ext/wasm/c-pp-lite.c

/*
** 2022-11-12:
**
** The author disclaims copyright to this source code.  In place of
** a legal notice, here is a blessing:
**
**  * May you do good and not evil.
**  * May you find forgiveness for yourself and forgive others.
**  * May you share freely, never taking more than you give.
**
************************************************************************
**
** The C-minus Preprocessor: a truly minimal C-like preprocessor.
** Why? Because C preprocessors _can_ process non-C code but generally make
** quite a mess of it. The purpose of this application is an extremely
** minimal preprocessor with only the most basic functionality of a C
** preprocessor, namely.
**
** The supported preprocessor directives are documented in the
** README.md hosted with this file.
**
** Any mention of "#" in the docs, e.g. "#if", is symbolic. The
** directive delimiter is configurable and defaults to "##". Define
** CMPP_DEFAULT_DELIM to a string when compiling to define the default
** at build-time.
**
** This preprocessor has only minimal support for replacement of tokens
** which live in the "content" blocks of inputs (that is, the pieces
** which are not prepocessor lines).
**
** See this file's README.md for details.
**
** Design note: this code makes use of sqlite3. Though not _strictly_
** needed in order to implement it, this tool was specifically created
** for use with the sqlite3 project's own JavaScript code, so there's
** no reason not to make use of it to do some of the heavy lifting. It
** does not require any cutting-edge sqlite3 features and should be
** usable with any version which supports `WITHOUT ROWID`.
**
** Author(s):
**
** - Stephan Beal <https://wanderinghorse.net/home/stephan/>
**
** Canonical homes:
**
** - https://fossil.wanderinghorse.net/r/c-pp
** - https://sqlite.org/src/file/ext/wasm/c-pp.c
**
** With the former hosting this app's SCM and the latter being the
** single known deployment of c-pp.c, where much of its development
** happens.
*/

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdarg.h>
#include <assert.h>
#include <ctype.h>

#include "sqlite3.h"

#if defined(_WIN32) || defined(WIN32)
#  include <io.h>
#  include <fcntl.h>
#  ifndef access
#    define access(f,m) _access((f),(m))
#  endif
#else
#  include <unistd.h>
#endif

#ifndef CMPP_DEFAULT_DELIM
#define CMPP_DEFAULT_DELIM "##"
#endif

#ifndef CMPP_ATSIGN
#define CMPP_ATSIGN (unsigned char)'@'
#endif

#if 1
#  define CMPP_NORETURN __attribute__((noreturn))
#else
#  define CMPP_NORETURN
#endif

/* Fatally exits the app with the given printf-style message. */
static CMPP_NORETURN void fatalv__base(char const *zFile, int line,
                                      char const *zFmt, va_list);
static CMPP_NORETURN void fatal__base(char const *zFile, int line,
                                      char const *zFmt, ...);
#define fatalv(...) fatalv__base(__FILE__,__LINE__,__VA_ARGS__)
#define fatal(...) fatal__base(__FILE__,__LINE__,__VA_ARGS__)

/** Proxy for free(), for symmetry with cmpp_realloc(). */
static void cmpp_free(void *p);
/** A realloc() proxy which dies fatally on allocation error. */
static void * cmpp_realloc(void * p, unsigned n);
#if 0
/** A malloc() proxy which dies fatally on allocation error. */
static void * cmpp_malloc(unsigned n);
#endif

static void check__oom2(void const *p, char const *zFile, int line){
  if(!p) fatal("Alloc failed at %s:%d", zFile, line);
}
#define check__oom(P) check__oom2((P), __FILE__, __LINE__)

/*
** If p is stdin or stderr then this is a no-op, else it is a
** proxy for fclose(). This is a no-op if p is NULL.
*/
static void FILE_close(FILE *p);
/*
** Works like fopen() but accepts the special name "-" to mean either
** stdin (if zMode indicates a real-only mode) or stdout. Fails
** fatally on error.
*/
static FILE * FILE_open(char const *zName, const char * zMode);
/*
** Reads the entire contents of the given file, allocating it in a
** buffer which gets assigned to `*pOut`. `*nOut` gets assigned the
** length of the output buffer. Fails fatally on error.
*/
static void FILE_slurp(FILE *pFile, unsigned char **pOut,
                       unsigned * nOut);

/*
** Intended to be passed an sqlite3 result code. If it's a non-0 value
** other than SQLITE_ROW or SQLITE_DONE then it emits a fatal error
** message which contains both the given string and the
** sqlite3_errmsg() from the application's database instance.
*/
static void db_affirm_rc(int rc, const char * zMsg);

/*
** Proxy for sqlite3_str_finish() which fails fatally if that
** routine returns NULL.
*/
static char * db_str_finish(sqlite3_str *s, int * n);
/*
** Proxy for sqlite3_str_new() which fails fatally if that
** routine returns NULL.
*/
static sqlite3_str * db_str_new(void);

/*
** Proxy for sqlite3_step() which fails fatally if the result
** is anything other than SQLITE_ROW or SQLITE_DONE.
*/
static int db_step(sqlite3_stmt *pStmt);
/*
** Proxy for sqlite3_bind_int() which fails fatally on error.
*/
static void db_bind_int(sqlite3_stmt *pStmt, int col, int val);
/*
** Proxy for sqlite3_bind_null() which fails fatally on error.
*/
static void db_bind_null(sqlite3_stmt *pStmt, int col);
/*
** Proxy for sqlite3_bind_text() which fails fatally on error.
*/
static void db_bind_text(sqlite3_stmt *pStmt, int col, const char * zStr);
/*
** Proxy for sqlite3_bind_text() which fails fatally on error.
*/
static void db_bind_textn(sqlite3_stmt *pStmt, int col, const char * zStr, int len);
#if 0
/*
** Proxy for sqlite3_bind_text() which fails fatally on error. It uses
** sqlite3_str_vappendf() so supports all of its formatting options.
*/
static void db_bind_textv(sqlite3_stmt *pStmt, int col, const char * zFmt, ...);
#endif
/*
** Proxy for sqlite3_free(), to be passed any memory which is allocated
** by sqlite3_malloc().
*/
static void db_free(void *m);

/*
** Returns true if the first nKey bytes of zKey are a legal string. If
** it returns false and zErrPos is not null, *zErrPos is set to the
** position of the illegal character. If nKey is negative, strlen() is
** used to calculate it.
*/
static int cmpp_is_legal_key(char const *zKey, int nKey, char const **zErrPos);

/*
** Fails fatally if !cmpp_is_legal_key(zKey).
*/
static void cmpp_affirm_legal_key(char const *zKey, int nKey);

/*
** Adds the given `#define` macro name to the list of macros, ignoring
** any duplicates. Fails fatally on error.
**
** If zVal is NULL then zKey may contain an '=', from which the value
** will be extracted. If zVal is not NULL then zKey may _not_ contain
** an '='.
*/
static void db_define_add(const char * zKey, char const *zVal);

/*
** Returns true if the given key is already in the `#define` list,
** else false. Fails fatally on db error.
**
** nName is the length of the key part of zName (which might have
** a following =y part. If it's negative, strlen() is used to
** calculate it.
*/
static int db_define_has(const char * zName, int nName);

/*
** Returns true if the given key is already in the `#define` list, and
** it has a truthy value (is not empty and not equal to '0'), else
** false. Fails fatally on db error.
**
** nName is the length of zName, or <0 to use strlen() to figure
** it out.
*/
static int db_define_get_bool(const char * zName, int nName);

/*
** Searches for a define where (k GLOB zName). If one is found, a copy
** of it is assigned to *zVal (the caller must eventually db_free()
** it)), *nVal (if nVal is not NULL) is assigned its strlen, and
** returns non-0. If no match is found, 0 is returned and neither
** *zVal nor *nVal are modified. If more than one result matches, a
** fatal error is triggered.
**
** It is legal for *zVal to be NULL (and *nVal to be 0) if it returns
** non-0. That just means that the key was defined with no value part.
*/
static int db_define_get(const char * zName, int nName, char **zVal, unsigned int *nVal);

/*
** Removes the given `#define` macro name from the list of
** macros. Fails fatally on error.
*/
static void db_define_rm(const char * zKey);
/*
** Adds the given filename to the list of being-`#include`d files,
** using the given source file name and line number of error reporting
** purposes. If recursion is later detected.
*/
static void db_including_add(const char * zKey, const char * zSrc, int srcLine);
/*
** Adds the given dir to the list of includes. They are checked in the
** order they are added.
*/
static void db_include_dir_add(const char * zKey);
/*
** Returns a resolved path of PREFIX+'/'+zKey, where PREFIX is one of
** the `#include` dirs (db_include_dir_add()). If no file match is
** found, NULL is returned. Memory must eventually be passed to
** db_free() to free it.
*/
static char * db_include_search(const char * zKey);
/*
** Removes the given key from the `#include` list.
*/
static void db_include_rm(const char * zKey);
/*
** A proxy for sqlite3_prepare() which fails fatally on error.
*/
static void db_prepare(sqlite3_stmt **pStmt, const char * zSql, ...);

/*
** Opens the given file and processes its contents as c-pp, sending
** all output to the global c-pp output channel. Fails fatally on
** error. If bRaw is true then the file's contents are passed through
** verbatim, rather than being preprocessed.
*/
static void cmpp_process_file(const char * zName, int bRaw);

/*
** Operator policy for cmpp_kvp_parse().
*/
enum cmpp_key_op_e {
  /* Fail if the key contains an operator. */
  cmpp_key_op_none,
  /* Accept only '='. */
  cmpp_key_op_eq1
};
typedef enum cmpp_key_op_e cmpp_key_op_e;

/*
** Operators and operator policies for use with X=Y-format keys.
*/
#define cmpp_kvp_op_map(E) \
  E(none,"")               \
  E(eq1,"=")               \
  E(eq2,"==")              \
  E(lt,"<")                \
  E(le,"<=")               \
  E(gt,">")                \
  E(ge,">=")

enum cmpp_kvp_op_e {
#define E(N,S) cmpp_kvp_op_ ## N,
  cmpp_kvp_op_map(E)
#undef E
};
typedef enum cmpp_kvp_op_e cmpp_kvp_op_e;

/*
** A snippet from a string.
*/
struct cmpp_snippet {
  char const *z;
  unsigned int n;
};
typedef struct cmpp_snippet cmpp_snippet;
#define cmpp_snippet_empty_m {0,0}

/*
** Result type for cmpp_kvp_parse().
*/
struct cmpp_kvp {
  cmpp_snippet k;
  cmpp_snippet v;
  cmpp_kvp_op_e op;
};

typedef struct cmpp_kvp cmpp_kvp;
#define cmpp_kvp_empty_m \
  {cmpp_snippet_empty_m,cmpp_snippet_empty_m,cmpp_kvp_op_none}
static const cmpp_kvp cmpp_kvp_empty = cmpp_kvp_empty_m;

/*
** Parses X or X=Y into p. Fails fatally on error.
**
** If nKey is negative then strlen() is used to calculate it.
**
** The third argument specifies whether/how to permit/treat the '='
** part of X=Y.
*/
static void cmpp_kvp_parse(cmpp_kvp * p,
                           char const *zKey, int nKey,
                           cmpp_kvp_op_e opPolicy);

/*
** Wrapper around a FILE handle.
*/
typedef struct FileWrapper FileWrapper;
struct FileWrapper {
  /* File's name. */
  char const *zName;
  /* FILE handle. */
  FILE * pFile;
  /* Where FileWrapper_slurp() stores the file's contents. */
  unsigned char * zContent;
  /* Size of this->zContent, as set by FileWrapper_slurp(). */
  unsigned nContent;
  /* See Global::pFiles. */
  FileWrapper * pTail;
};
#define FileWrapper_empty_m {0,0,0,0,0}
static const FileWrapper FileWrapper_empty = FileWrapper_empty_m;

/*
** Proxy for FILE_close() and frees all memory owned by p. A no-op if
** p is already closed.
*/
static void FileWrapper_close(FileWrapper * p);
/* Proxy for FILE_open(). Closes p first if it's currently opened. */
static void FileWrapper_open(FileWrapper * p, const char * zName, const char *zMode);
/* Proxy for FILE_slurp(). */
static void FileWrapper_slurp(FileWrapper * p);
/*
** If p->zContent ends in \n or \r\n, that part is replaced with 0 and
** p->nContent is adjusted. Returns true if it chomps, else false.
*/
int FileWrapper_chomp(FileWrapper * p);

/*
** Outputs a printf()-formatted message to stderr.
*/
static void g_stderr(char const *zFmt, ...);
/*
** Outputs a printf()-formatted message to stderr.
*/
static void g_stderrv(char const *zFmt, va_list);
#define g_debug(lvl,pfexpr)                                          \
  if(lvl<=g.flags.doDebug) g_stderr("%s @ %s():%d: ",g.zArgv0,__func__,__LINE__); \
  if(lvl<=g.flags.doDebug) g_stderr pfexpr

#define g_warn(zFmt,...) g_stderr("%s:%d %s() " zFmt "\n", __FILE__, __LINE__, __func__, __VA_ARGS__)
#define g_warn0(zMsg) g_stderr("%s:%d %s() %s\n", __FILE__, __LINE__, __func__, zMsg)

void cmpp_free(void *p){
  sqlite3_free(p);
}

void * cmpp_realloc(void * p, unsigned n){
  void * const rc = sqlite3_realloc(p, n);
  if(!rc) fatal("realloc(P,%u) failed", n);
  return rc;
}

#if 0
void * cmpp_malloc(unsigned n){
  void * const rc = sqlite3_alloc(n);
  if(!rc) fatal("malloc(%u) failed", n);
  return rc;
}
#endif

FILE * FILE_open(char const *zName, const char * zMode){
  FILE * p;
  if('-'==zName[0] && 0==zName[1]){
    p = strstr(zMode,"w") ? stdout : stdin;
  }else{
    p = fopen(zName, zMode);
    if(!p) fatal("Cannot open file [%s] with mode [%s]", zName, zMode);
  }
  return p;
}

void FILE_close(FILE *p){
  if(p && p!=stdout && p!=stderr){
    fclose(p);
  }
}

void FILE_slurp(FILE *pFile, unsigned char **pOut,
                unsigned * nOut){
  unsigned char zBuf[1024 * 8];
  unsigned char * pDest = 0;
  unsigned nAlloc = 0;
  unsigned nOff = 0;
  /* Note that this needs to be able to work on non-seekable streams,
  ** thus we read in chunks instead of doing a single alloc and
  ** filling it in one go. */
  while( !feof(pFile) ){
    size_t const n = fread(zBuf, 1, sizeof(zBuf), pFile);
    if(n>0){
      if(nAlloc < nOff + n + 1){
        nAlloc = nOff + n + 1;
        pDest = cmpp_realloc(pDest, nAlloc);
      }
      memcpy(pDest + nOff, zBuf, n);
      nOff += n;
    }
  }
  if(pDest) pDest[nOff] = 0;
  *pOut = pDest;
  *nOut = nOff;
}

void FileWrapper_close(FileWrapper * p){
  if(p->pFile) FILE_close(p->pFile);
  if(p->zContent) cmpp_free(p->zContent);
  *p = FileWrapper_empty;
}

void FileWrapper_open(FileWrapper * p, const char * zName,
                      const char * zMode){
  FileWrapper_close(p);
  p->pFile = FILE_open(zName, zMode);
  p->zName = zName;
}

void FileWrapper_slurp(FileWrapper * p){
  assert(!p->zContent);
  assert(p->pFile);
  FILE_slurp(p->pFile, &p->zContent, &p->nContent);
}

int FileWrapper_chomp(FileWrapper * p){
  if( p->nContent && '\n'==p->zContent[p->nContent-1] ){
    p->zContent[--p->nContent] = 0;
    if( p->nContent && '\r'==p->zContent[p->nContent-1] ){
      p->zContent[--p->nContent] = 0;
    }
    return 1;
  }
  return 0;
}

enum CmppParseState {
TS_Start = 1,
TS_If,
TS_IfPassed,
TS_Else,
TS_Error
};
typedef enum CmppParseState CmppParseState;
enum CmppTokenType {

#define CmppToken_map(E) \
  E(Invalid,0)           \
  E(Assert,"assert")     \
  E(AtPolicy,"@policy")  \
  E(Comment,"//")        \
  E(Define,"define")     \
  E(Elif,"elif")         \
  E(Else,"else")         \
  E(Endif,"endif")       \
  E(Error,"error")       \
  E(If,"if")             \
  E(Include,"include")   \
  E(Line,0)              \
  E(Opaque,0)            \
  E(Pragma,"pragma")     \
  E(Savepoint,"savepoint") \
  E(Stderr,"stderr")     \
  E(Undef,"undef")

#define E(N,TOK) TT_ ## N,
  CmppToken_map(E)
#undef E
};
typedef enum CmppTokenType CmppTokenType;

/*
** Map of directive (formerly keyword) names and their token types.
*/
static const struct {
#define E(N,TOK) struct cmpp_snippet N;
  CmppToken_map(E)
#undef E
} DStrings = {
#define E(N,TOK) .N = {TOK,sizeof(TOK)-1},
  CmppToken_map(E)
#undef E
};

//static
char const * TT_cstr(int tt){
  switch(tt){
#define E(N,TOK) case TT_ ## N: return DStrings.N.z;
    CmppToken_map(E)
#undef E
  }
  return NULL;
}

struct CmppToken {
  CmppTokenType ttype;
  /* Line number of this token in the source file. */
  unsigned lineNo;
  /* Start of the token. */
  unsigned char const * zBegin;
  /* One-past-the-end byte of the token. */
  unsigned char const * zEnd;
};
typedef struct CmppToken CmppToken;
#define CmppToken_empty_m {TT_Invalid,0,0,0}
static const CmppToken CmppToken_empty = CmppToken_empty_m;

/*
** CmppLevel represents one "level" of tokenization, starting at the
** top of the main input, incrementing once for each level of `#if`,
** and decrementing for each `#endif`.
** pushes a level.
*/
typedef struct CmppLevel CmppLevel;
struct CmppLevel {
  unsigned short flags;
  /*
  ** Used for controlling which parts of an if/elif/...endif chain
  ** should get output.
  */
  unsigned short skipLevel;
  /* The token which started this level (an 'if' or 'include'). */
  CmppToken token;
  CmppParseState pstate;
};
#define CmppLevel_empty_m {0U,0U,CmppToken_empty_m,TS_Start}
static const CmppLevel CmppLevel_empty = CmppLevel_empty_m;
enum CmppLevel_Flags {
/* Max depth of nested `#if` constructs in a single tokenizer. */
CmppLevel_Max = 10,
/* Max number of keyword arguments. */
CmppArgs_Max = 15,
/* Directive line buffer size */
CmppArgs_BufSize = 1024,
/* Flag indicating that output for a CmpLevel should be elided. */
CmppLevel_F_ELIDE = 0x01,
/*
** Mask of CmppLevel::flags which are inherited when CmppLevel_push()
** is used.
*/
CmppLevel_F_INHERIT_MASK = CmppLevel_F_ELIDE
};

typedef struct CmppTokenizer CmppTokenizer;
typedef struct CmppKeyword CmppKeyword;
typedef void (*cmpp_keyword_f)(CmppKeyword const * pKw, CmppTokenizer * t);
struct CmppKeyword {
  const char *zName;
  unsigned nName;
  int bTokenize;
  CmppTokenType ttype;
  cmpp_keyword_f xCall;
};

static CmppKeyword const * CmppKeyword_search(const char *zName);
static void cmpp_process_keyword(CmppTokenizer * const t);

/*
** Tokenizer for c-pp input files.
*/
struct CmppTokenizer {
  const char * zName;            /* Input (file) name for error reporting */
  unsigned const char * zBegin;  /* start of input */
  unsigned const char * zEnd;    /* one-after-the-end of input */
  unsigned const char * zPos;    /* current position */
  unsigned int lineNo;           /* line # of current pos */
  unsigned nSavepoint;
  CmppParseState pstate;
  CmppToken token;               /* current token result */
  struct {
    unsigned ndx;
    CmppLevel stack[CmppLevel_Max];
  } level;
  /* Args for use in cmpp_keyword_f() impls. */
  struct {
    CmppKeyword const * pKw;
    int argc;
    const unsigned char * argv[CmppArgs_Max];
    unsigned char lineBuf[CmppArgs_BufSize];
  } args;
};
#define CT_level(t) (t)->level.stack[(t)->level.ndx]
#define CT_pstate(t) CT_level(t).pstate
#define CT_skipLevel(t) CT_level(t).skipLevel
#define CLvl_skip(lvl) ((lvl)->skipLevel || ((lvl)->flags & CmppLevel_F_ELIDE))
#define CT_skip(t) CLvl_skip(&CT_level(t))
#define CmppTokenizer_empty_m {         \
    .zName=0, .zBegin=0, .zEnd=0,       \
    .zPos=0,                            \
    .lineNo=1U,                         \
    .pstate = TS_Start,                 \
    .token = CmppToken_empty_m,         \
    .level = {0U,{CmppLevel_empty_m}},  \
    .args = {0,0,{0},{0}}               \
  }
static const CmppTokenizer CmppTokenizer_empty = CmppTokenizer_empty_m;

static void CmppTokenizer_cleanup(CmppTokenizer * const t);

static void cmpp_t_out(CmppTokenizer * t, void const *z, unsigned int n);
/*static void cmpp_t_outf(CmppTokenizer * t, char const *zFmt, ...);*/

/*
** Pushes a new level into the given tokenizer. Fails fatally if
** it's too deep.
*/
static void CmppLevel_push(CmppTokenizer * const t);
/*
** Pops a level from the tokenizer. Fails fatally if the top
** level is popped.
*/
static void CmppLevel_pop(CmppTokenizer * const t);
/*
** Returns the current level object.
*/
static CmppLevel * CmppLevel_get(CmppTokenizer * const t);

/*
** Policies for how to handle undefined @tokens@ when performing
** content filtering.
*/
enum AtPolicy {
  AT_invalid = -1,
  /** Turn off @foo@ parsing. */
  AT_OFF = 0,
  /** Retain undefined @foo@ - emit it as-is. */
  AT_RETAIN,
  /** Elide undefined @foo@. */
  AT_ELIDE,
  /** Error for undefined @foo@. */
  AT_ERROR,
  AT_DEFAULT = AT_ERROR
};
typedef enum AtPolicy AtPolicy;

static AtPolicy AtPolicy_fromStr(char const *z, int bEnforce){
  if( 0==strcmp(z, "retain") ) return AT_RETAIN;
  if( 0==strcmp(z, "elide") ) return AT_ELIDE;
  if( 0==strcmp(z, "error") ) return AT_ERROR;
  if( 0==strcmp(z, "off") ) return AT_OFF;
  if( bEnforce ){
    fatal("Invalid @ policy value: %s. "
          "Try one of retain|elide|error|off.", z);
  }
  return AT_invalid;
}

/*
** Global app state singleton.
*/
static struct Global {
  /* main()'s argv[0]. */
  const char * zArgv0;
  /* App's db instance. */
  sqlite3 * db;
  /* Current tokenizer (for error reporting purposes). */
  CmppTokenizer const * tok;
  /*
  ** We use a linked-list of these to keep track of our opened
  ** files so that we can clean then up via atexit() in the case of
  ** fatal error (to please valgrind).
  */
  FileWrapper * pFiles;
  /* Output channel. */
  FileWrapper out;
  struct {
    /*
    ** Bytes of the keyword delimiter/prefix. Owned
    ** elsewhere.
    */
    const char * z;
    /* Byte length of this->zDelim. */
    unsigned short n;
    /*
    ** The @token@ delimiter.
    **
    ** Potential TODO is replace this with a pair of opener/closer
    ** strings, e.g. "{{" and "}}".
    */
    const unsigned char chAt;
  } delim;
  struct {
#define CMPP_SAVEPOINT_NAME "_cmpp_"
#define GStmt_map(E)               \
    E(defIns,"INSERT OR REPLACE INTO def(k,v) VALUES(?,?)") \
    E(defDel,"DELETE FROM def WHERE k GLOB ?")         \
    E(defHas,"SELECT 1 FROM def WHERE k GLOB ?")       \
    E(defGet,"SELECT k,v FROM def WHERE k GLOB ?")     \
    E(defGetBool,                                      \
      "SELECT 1 FROM def WHERE k = ?1"                 \
      " AND v IS NOT NULL"                             \
      " AND '0'!=v AND ''!=v")                         \
    E(defSelAll,"SELECT k,v FROM def ORDER BY k")      \
    E(inclIns,"INSERT OR FAIL INTO incl(file,srcFile," \
      "srcLine) VALUES(?,?,?)")                        \
    E(inclDel,"DELETE FROM incl WHERE file=?")         \
    E(inclHas,"SELECT 1 FROM incl WHERE file=?")       \
    E(inclPathAdd,"INSERT OR FAIL INTO "               \
      "inclpath(seq,dir) VALUES(?,?)")                 \
    E(inclSearch,                                      \
      "SELECT ?1 fn WHERE fileExists(fn) "             \
      "UNION ALL SELECT * FROM ("                      \
      "SELECT replace(dir||'/'||?1, '//','/') AS fn "  \
      "FROM inclpath WHERE fileExists(fn) ORDER BY seq"\
      ")")                                             \
    E(spBegin,"SAVEPOINT " CMPP_SAVEPOINT_NAME)        \
    E(spRollback,"ROLLBACK TO SAVEPOINT "              \
      CMPP_SAVEPOINT_NAME)                             \
    E(spRelease,"RELEASE SAVEPOINT " CMPP_SAVEPOINT_NAME)

#define E(N,S) sqlite3_stmt * N;
    GStmt_map(E)
#undef E
  } stmt;
  struct {
    FILE * pFile;
    int expandSql;
  } sqlTrace;
  struct {
    AtPolicy atPolicy;
    /* If true, enables certain debugging output. */
    char doDebug;
    /* If true, chomp() files read via -Fx=file. */
    char chompF;
  } flags;
} g = {
  .zArgv0 = "?",
  .db = 0,
  .tok = 0,
  .pFiles = 0,
  .out = FileWrapper_empty_m,
  .delim = {
    .z = CMPP_DEFAULT_DELIM,
    .n = (unsigned short) sizeof(CMPP_DEFAULT_DELIM)-1,
    .chAt = '@'
  },
  .stmt = {
    .defIns =   0,
    .defDel = 0,
    .defHas = 0,
    .defGet = 0,
    .defGetBool = 0,
    .inclIns =   0,
    .inclDel =   0,
    .inclHas =   0,
    .inclPathAdd =   0,
    .inclSearch =   0
  },
  .sqlTrace = {
    .pFile = 0,
    .expandSql = 0
  },
  .flags = {
    .atPolicy = AT_OFF,
    .doDebug = 0,
    .chompF = 0
  }
};

/** Distinct IDs for each g.stmt member. */
enum GStmt_e {
  GStmt_none = 0,
#define E(N,S) GStmt_ ## N,
  GStmt_map(E)
#undef E
};

/*
** Returns the g.stmt.X corresponding to `which`, initializing it if
** needed. It does not return NULL - it fails fatally on error.
*/
static sqlite3_stmt * g_stmt(enum GStmt_e which){
  sqlite3_stmt ** q = 0;
  char const * zSql = 0;
  switch(which){
    case GStmt_none:
      fatal("GStmt_none is not a valid statement handle");
      return NULL;
#define E(N,S) case GStmt_ ## N: zSql = S; q = &g.stmt.N; break;
    GStmt_map(E)
#undef E
  }
  assert( q );
  assert( zSql && *zSql );
  if( !*q ){
    db_prepare(q, "%s", zSql);
    assert( *q );
  }
  return *q;
}
static void g_stmt_reset(sqlite3_stmt * const q){
  sqlite3_clear_bindings(q);
  sqlite3_reset(q);
}

#if 0
/*
** Outputs a printf()-formatted message to c-pp's global output
** channel.
*/
static void g_outf(char const *zFmt, ...);
void g_outf(char const *zFmt, ...){
  va_list va;
  va_start(va, zFmt);
  vfprintf(g.out.pFile, zFmt, va);
  va_end(va);
}
#endif

/* Outputs n bytes from z to c-pp's global output channel. */
static void g_out(void const *z, unsigned int n);
void g_out(void const *z, unsigned int n){
  if(g.out.pFile && 1!=fwrite(z, n, 1, g.out.pFile)){
    int const err = errno;
    fatal("fwrite() output failed with errno #%d", err);
  }
}

void g_stderrv(char const *zFmt, va_list va){
  if( g.out.pFile==stdout ){
    fflush(g.out.pFile);
  }
  vfprintf(stderr, zFmt, va);
}

void g_stderr(char const *zFmt, ...){
  va_list va;
  va_start(va, zFmt);
  g_stderrv(zFmt, va);
  va_end(va);
}

/*
** Emits n bytes of z if CT_skip(t) is false.
*/
void cmpp_t_out(CmppTokenizer * t, void const *z, unsigned int n){
  g_debug(3,("CT_skipLevel() ?= %d\n",CT_skipLevel(t)));
  g_debug(3,("CT_skip() ?= %d\n",CT_skip(t)));
  if(!CT_skip(t)) g_out(z, n);
}

void CmppLevel_push(CmppTokenizer * const t){
  CmppLevel * pPrev;
  CmppLevel * p;
  if(t->level.ndx+1 == (unsigned)CmppLevel_Max){
    fatal("%sif nesting level is too deep. Max=%d\n",
          g.delim.z, CmppLevel_Max);
  }
  pPrev = &CT_level(t);
  g_debug(3,("push from tokenizer level=%u flags=%04x\n",
             t->level.ndx, pPrev->flags));
  p = &t->level.stack[++t->level.ndx];
  *p = CmppLevel_empty;
  p->token = t->token;
  p->flags = (CmppLevel_F_INHERIT_MASK & pPrev->flags);
  if(CLvl_skip(pPrev)) p->flags |= CmppLevel_F_ELIDE;
  g_debug(3,("push to tokenizer level=%u flags=%04x\n",
             t->level.ndx, p->flags));
}

void CmppLevel_pop(CmppTokenizer * const t){
  if(!t->level.ndx){
    fatal("Internal error: CmppLevel_pop() at the top of the stack");
  }
  g_debug(3,("pop from tokenizer level=%u, flags=%04x skipLevel?=%d\n",
             t->level.ndx,
             t->level.stack[t->level.ndx].flags, CT_skipLevel(t)));
  g_debug(3,("CT_skipLevel() ?= %d\n",CT_skipLevel(t)));
  g_debug(3,("CT_skip() ?= %d\n",CT_skip(t)));
  t->level.stack[t->level.ndx--] = CmppLevel_empty;
  g_debug(3,("pop to tokenizer level=%u, flags=%04x\n", t->level.ndx,
             t->level.stack[t->level.ndx].flags));
  g_debug(3,("CT_skipLevel() ?= %d\n",CT_skipLevel(t)));
  g_debug(3,("CT_skip() ?= %d\n",CT_skip(t)));
}

CmppLevel * CmppLevel_get(CmppTokenizer * const t){
  return &t->level.stack[t->level.ndx];
}


void db_affirm_rc(int rc, const char * zMsg){
  switch(rc){
    case 0:
    case SQLITE_DONE:
    case SQLITE_ROW:
      break;
    default:
      assert( g.db );
      fatal("Db error #%d %s: %s", rc, zMsg,
            sqlite3_errmsg(g.db));
  }
}

int db_step(sqlite3_stmt *pStmt){
  int const rc = sqlite3_step(pStmt);
  switch( rc ){
    case SQLITE_ROW:
    case SQLITE_DONE:
      break;
    default:
      db_affirm_rc(rc, "from db_step()");
  }
  return rc;
}

static sqlite3_str * db_str_new(void){
  sqlite3_str * rc = sqlite3_str_new(g.db);
  if(!rc) fatal("Alloc failed for sqlite3_str_new()");
  return rc;
}

static char * db_str_finish(sqlite3_str *s, int * n){
  int const rc = sqlite3_str_errcode(s);
  if(rc) fatal("Error #%d from sqlite3_str_errcode()", rc);
  if(n) *n = sqlite3_str_length(s);
  char * z = sqlite3_str_finish(s);
  if(!z) fatal("Alloc failed for sqlite3_str_new()");
  return z;
}

void db_prepare(sqlite3_stmt **pStmt, const char * zSql, ...){
  int rc;
  sqlite3_str * str = db_str_new();
  char * z = 0;
  int n = 0;
  va_list va;
  va_start(va, zSql);
  sqlite3_str_vappendf(str, zSql, va);
  va_end(va);
  rc = sqlite3_str_errcode(str);
  if(rc) fatal("sqlite3_str_errcode() = %d", rc);
  z = db_str_finish(str, &n);
  rc = sqlite3_prepare_v2(g.db, z, n, pStmt, 0);
  if(rc) fatal("Error #%d (%s) preparing: %s",
               rc, sqlite3_errmsg(g.db), z);
  sqlite3_free(z);
}

void db_bind_int(sqlite3_stmt *pStmt, int col, int val){
  db_affirm_rc(sqlite3_bind_int(pStmt, col, val),
               "from db_bind_int()");
}

void db_bind_null(sqlite3_stmt *pStmt, int col){
  db_affirm_rc(sqlite3_bind_null(pStmt, col),
               "from db_bind_null()");
}

void db_bind_textn(sqlite3_stmt *pStmt, int col,
                   const char * zStr, int n){
  db_affirm_rc(
    (zStr && n)
    ? sqlite3_bind_text(pStmt, col, zStr, n, SQLITE_TRANSIENT)
    : sqlite3_bind_null(pStmt, col),
    "from db_bind_textn()"
  );
}

void db_bind_text(sqlite3_stmt *pStmt, int col,
                  const char * zStr){
  db_bind_textn(pStmt, col, zStr, -1);
}

#if 0
void db_bind_textv(sqlite3_stmt *pStmt, int col,
                   const char * zFmt, ...){
  int rc;
  sqlite3_str * str = db_str_new();
  int n = 0;
  char * z;
  va_list va;
  va_start(va,zFmt);
  sqlite3_str_vappendf(str, zFmt, va);
  va_end(va);
  z = db_str_finish(str, &n);
  rc = sqlite3_bind_text(pStmt, col, z, n, sqlite3_free);
  db_affirm_rc(rc,"from db_bind_textv()");
}
#endif

void db_free(void *m){
  sqlite3_free(m);
}

void db_define_add(const char * zKey, char const *zVal){
  cmpp_kvp kvp = cmpp_kvp_empty;
  cmpp_kvp_parse(&kvp, zKey, -1,
    zVal
    ? cmpp_key_op_none
    : cmpp_key_op_eq1
  );
  if( kvp.v.z ){
    if( zVal ){
      assert(!"cannot happen - cmpp_key_op_none will prevent it");
      fatal("Cannot assign two values to [%.*s] [%.*s] [%s]",
            kvp.k.n, kvp.k.z, kvp.v.n, kvp.v.z, zVal);
    }
  }else{
    kvp.v.z = zVal;
    kvp.v.n = zVal ? (int)strlen(zVal) : 0;
  }
  sqlite3_stmt * const q = g_stmt(GStmt_defIns);
  //g_stderr("zKey=%s\nzVal=%s\nzEq=%s\n", zKey, zVal, zEq);
  db_bind_textn(q, 1, kvp.k.z, kvp.k.n);
  if( kvp.v.z ){
    if( kvp.v.n ){
      db_bind_textn(q, 2, kvp.v.z, (int)kvp.v.n);
    }else{
      db_bind_null(q, 2);
    }
  }else{
    db_bind_int(q, 2, 1);
  }
  db_step(q);
  g_debug(2,("define: %s%s%s\n",
             zKey,
             zVal ? " with value " : "",
             zVal ? zVal : ""));
  sqlite3_reset(q);
}

static void db_define_add_file(const char * zKey){
  cmpp_kvp kvp = cmpp_kvp_empty;
  cmpp_kvp_parse(&kvp, zKey, -1, cmpp_kvp_op_eq1);
  if( !kvp.v.z || !kvp.v.n ){
    fatal("Invalid filename: %s", zKey);
  }
  sqlite3_stmt * q = 0;
  FileWrapper fw = FileWrapper_empty;
  FileWrapper_open(&fw, kvp.v.z, "r");
  FileWrapper_slurp(&fw);
  q = g_stmt(GStmt_defIns);
  //g_stderr("zKey=%s\nzVal=%s\nzEq=%s\n", zKey, zVal, zEq);
  db_bind_textn(q, 1, kvp.k.z, (int)kvp.k.n);
  if( g.flags.chompF ){
    FileWrapper_chomp(&fw);
  }
  if( fw.nContent ){
    db_affirm_rc(
      sqlite3_bind_text(q, 2,
                        (char const *)fw.zContent,
                        (int)fw.nContent, sqlite3_free),
      "binding file content");
    fw.zContent = 0 /* transfered ownership */;
    fw.nContent = 0;
  }else{
    db_affirm_rc( sqlite3_bind_null(q, 2),
                  "binding empty file content");
  }
  FileWrapper_close(&fw);
  db_step(q);
  g_stmt_reset(q);
  g_debug(2,("define: %s%s%s\n",
             kvp.k.z,
             kvp.v.z ? " with value " : "",
             kvp.v.z ? kvp.v.z : ""));
}

#define ustr_c(X) ((unsigned char const *)X)

static inline unsigned int cmpp_strlen(char const *z, int n){
  return n<0 ? (int)strlen(z) : (unsigned)n;
}


int db_define_has(const char * zName, int nName){
  int rc;
  sqlite3_stmt * const q = g_stmt(GStmt_defHas);
  nName = cmpp_strlen(zName, nName);
  db_bind_textn(q, 1, zName, nName);
  rc = db_step(q);
  if(SQLITE_ROW == rc){
    rc = 1;
  }else{
    assert(SQLITE_DONE==rc);
    rc = 0;
  }
  g_debug(1,("defined [%s] ?= %d\n",zName, rc));
  g_stmt_reset(q);
  return rc;
}

int db_define_get_bool(const char * zName, int nName){
  sqlite3_stmt * const q = g_stmt(GStmt_defGetBool);
  int rc = 0;
  nName = cmpp_strlen(zName, nName);
  db_bind_textn(q, 1, zName, nName);
  rc = db_step(q);
  if(SQLITE_ROW == rc){
    if( SQLITE_ROW==sqlite3_step(q) ){
      fatal("Key is ambiguous: %s", zName);
    }
    rc = 1;
  }else{
    assert(SQLITE_DONE==rc);
    rc = 0;
  }
  g_stmt_reset(q);
  return rc;
}

int db_define_get(const char * zName, int nName,
                  char **zVal, unsigned int *nVal){
  sqlite3_stmt * q = g_stmt(GStmt_defGet);
  nName = cmpp_strlen(zName, nName);
  db_bind_textn(q, 1, zName, nName);
  int n = 0;
  int rc = db_step(q);
  if(SQLITE_ROW == rc){
    const unsigned char * z = sqlite3_column_text(q, 1);
    n = sqlite3_column_bytes(q,1);
    if( nVal ) *nVal = (unsigned)n;
    *zVal = sqlite3_mprintf("%.*s", n, z);
    if( n && z ) check__oom(*zVal);
    if( SQLITE_ROW==sqlite3_step(q) ){
      db_free(*zVal);
      *zVal = 0;
      fatal("Key is ambiguous: %.*s\n",
            nName, zName);
    }
    rc = 1;
  }else{
    assert(SQLITE_DONE==rc);
    rc = 0;
  }
  g_debug(1,("define [%.*s] ?= %d %.*s\n",
             nName, zName, rc,
             *zVal ? n : 0,
             *zVal ? *zVal : "<NULL>"));
  g_stmt_reset(q);
  return rc;
}

void db_define_rm(const char * zKey){
  int rc;
  int n = 0;
  sqlite3_stmt * const q = g_stmt(GStmt_defDel);
  db_bind_text(q, 1, zKey);
  rc = db_step(q);
  if(SQLITE_DONE != rc){
    db_affirm_rc(rc, "Stepping DELETE on def");
  }
  g_debug(2,("undefine: %.*s\n",n, zKey));
  g_stmt_reset(q);
}

void db_including_add(const char * zKey, const char * zSrc, int srcLine){
  int rc;
  sqlite3_stmt * const q = g_stmt(GStmt_inclIns);
  db_bind_text(q, 1, zKey);
  db_bind_text(q, 2, zSrc);
  db_bind_int(q, 3, srcLine);
  rc = db_step(q);
  if(SQLITE_DONE != rc){
    db_affirm_rc(rc, "Stepping INSERT on incl");
  }
  g_debug(2,("is-including-file add [%s] from [%s]:%d\n", zKey, zSrc, srcLine));
  g_stmt_reset(q);
}

void db_include_rm(const char * zKey){
  int rc;
  sqlite3_stmt * const q = g_stmt(GStmt_inclDel);
  db_bind_text(q, 1, zKey);
  rc = db_step(q);
  if(SQLITE_DONE != rc){
    db_affirm_rc(rc, "Stepping DELETE on incl");
  }
  g_debug(2,("inclpath rm [%s]\n", zKey));
  g_stmt_reset(q);
}

char * db_include_search(const char * zKey){
  char * zName = 0;
  sqlite3_stmt * const q = g_stmt(GStmt_inclSearch);
  db_bind_text(q, 1, zKey);
  if(SQLITE_ROW==db_step(q)){
    const unsigned char * z = sqlite3_column_text(q, 0);
    zName = z ? sqlite3_mprintf("%s", z) : 0;
    if(!zName) fatal("Alloc failed");
  }
  g_stmt_reset(q);
  return zName;
}

static int db_including_has(const char * zName){
  int rc;
  sqlite3_stmt * const q = g_stmt(GStmt_inclHas);
  db_bind_text(q, 1, zName);
  rc = db_step(q);
  if(SQLITE_ROW == rc){
    rc = 1;
  }else{
    assert(SQLITE_DONE==rc);
    rc = 0;
  }
  g_debug(2,("inclpath has [%s] = %d\n",zName, rc));
  g_stmt_reset(q);
  return rc;
}

#if 0
/*
** Fails fatally if the `#include` list contains the given key.
*/
static void db_including_check(const char * zKey);
void db_including_check(const char * zName){
  if(db_including_has(zName)){
    fatal("Recursive include detected: %s\n", zName);
  }
}
#endif

void db_include_dir_add(const char * zDir){
  static int seq = 0;
  int rc;
  sqlite3_stmt * const q = g_stmt(GStmt_inclPathAdd);
  db_bind_int(q, 1, ++seq);
  db_bind_text(q, 2, zDir);
  rc = db_step(q);
  if(SQLITE_DONE != rc){
    db_affirm_rc(rc, "Stepping INSERT on inclpath");
  }
  g_debug(2,("inclpath add #%d: %s\n",seq, zDir));
  g_stmt_reset(q);
}

void g_FileWrapper_link(FileWrapper *fp){
  assert(!fp->pTail);
  fp->pTail = g.pFiles;
  g.pFiles = fp;
}

void g_FileWrapper_close(FileWrapper *fp){
  assert(fp);
  assert(fp->pTail || g.pFiles==fp);
  g.pFiles = fp->pTail;
  fp->pTail = 0;
  FileWrapper_close(fp);
}

static void g_cleanup(int bCloseFileChain){
  if( g.db ){
#define E(N,S) sqlite3_finalize(g.stmt.N); g.stmt.N = 0;
  GStmt_map(E)
#undef E
  }
  if( bCloseFileChain ){
    FileWrapper * fpNext = 0;
    for( FileWrapper * fp=g.pFiles; fp; fp=fpNext ){
      fpNext = fp->pTail;
      fp->pTail = 0;
      FileWrapper_close(fp);
    }
  }
  FileWrapper_close(&g.out);
  if(g.db){
    sqlite3_close(g.db);
    g.db = 0;
  }
}

static void cmpp_atexit(void){
  g_cleanup(1);
}

int cmpp_is_legal_key(char const *zKey, int nKey, char const **zAt){
  char const * z = zKey;
  nKey = cmpp_strlen(zKey, nKey);
  if( !nKey ){
    if( zAt ) *zAt = z;
    return 0;
  }
  char const * const zEnd = z ? z + nKey : NULL;
  for( ; z < zEnd; ++z ){
    switch( (0x80 & *z) ? 0 : *z ){
      case 0:
      case '_':
        continue;
      case '-':
      case '.':
      case '/':
      case ':':
      case '=':
      case '0': case '1': case '2': case '3': case '4':
      case '5': case '6': case '7': case '8': case '9':
        if( z==zKey ) break;
        continue;
      default:
        if( isalpha((int)*z) ) continue;
    }
    if( zAt ) *zAt = z;
    return 0;
  }
  assert( z==zEnd );
  return 1;
}

void cmpp_affirm_legal_key(char const *zKey, int nKey){
  char const *zAt = 0;
  nKey = cmpp_strlen(zKey, nKey);
  if( !cmpp_is_legal_key(zKey, nKey, &zAt) ){
    assert( zAt );
    fatal("Illegal character 0x%02x in key [%.*s]\n",
          (int)*zAt, nKey, zKey);
  }
}

/*
** sqlite3 UDF which returns true if its argument refers to an
** accessible file, else false.
*/
static void udf_file_exists(
  sqlite3_context *context,
  int argc,
  sqlite3_value **argv
){
  const char *zName;
  (void)(argc);  /* Unused parameter */
  zName = (const char*)sqlite3_value_text(argv[0]);
  if( zName==0 ) return;
  sqlite3_result_int(context, 0==access(zName, 0));
}

/**
 ** This sqlite3_trace_v2() callback outputs tracing info using
 ** g.sqlTrace.pFile.
*/
static int cmpp__db_sq3TraceV2(unsigned t,void*c,void*p,void*x){
  static unsigned int counter = 0;
  switch(t){
    case SQLITE_TRACE_STMT:{
      FILE * const fp = g.sqlTrace.pFile;
      if( fp ){
        char const * const zSql = (char const *)x;
        char * const zExp = g.sqlTrace.expandSql
          ? sqlite3_expanded_sql((sqlite3_stmt*)p)
          : 0;
        fprintf(fp, "SQL TRACE #%u: %s\n",
                ++counter, zExp ? zExp : zSql);
        sqlite3_free(zExp);
      }
      break;
    }
  }
  return 0;
}

/* Initialize g.db, failing fatally on error. */
static void cmpp_initdb(void){
  int rc;
  char * zErr = 0;
  const char * zSchema =
    "CREATE TABLE def("
    /* ^^^ defines */
      "k TEXT PRIMARY KEY NOT NULL,"
      "v TEXT DEFAULT NULL"
    ") WITHOUT ROWID;"
    "CREATE TABLE incl("
    /* ^^^ files currently being included */
      "file TEXT PRIMARY KEY NOT NULL,"
      "srcFile TEXT DEFAULT NULL,"
      "srcLine INTEGER DEFAULT 0"
    ") WITHOUT ROWID;"
    "CREATE TABLE inclpath("
    /* ^^^ include path */
      "seq INTEGER UNIQUE ON CONFLICT IGNORE, "
      "dir TEXT PRIMARY KEY NOT NULL ON CONFLICT IGNORE"
    ");"
    "BEGIN;"
    ;
  assert(0==g.db);
  if(g.db) return;
  rc = sqlite3_open_v2(":memory:", &g.db, SQLITE_OPEN_READWRITE, 0);
  if(rc) fatal("Error opening :memory: db.");
  sqlite3_trace_v2(g.db, SQLITE_TRACE_STMT, cmpp__db_sq3TraceV2, 0);
  rc = sqlite3_exec(g.db, zSchema, 0, 0, &zErr);
  if(rc) fatal("Error initializing database: %s", zErr);
  rc = sqlite3_create_function(g.db, "fileExists", 1,
                               SQLITE_UTF8|SQLITE_DIRECTONLY, 0,
                               udf_file_exists, 0, 0);
  db_affirm_rc(rc, "UDF registration failed.");
}

/*
** For position zPos, which must be in the half-open range
** [zBegin,zEnd), returns g.delim.n if it is at the start of a line and
** starts with g.delim.z, else returns 0.
*/
//static
unsigned short cmpp_is_delim(unsigned char const *zBegin,
                                    unsigned char const *zEnd,
                                    unsigned char const *zPos){
  assert(zEnd>zBegin);
  assert(zPos<zEnd);
  assert(zPos>=zBegin);
  if(zPos>zBegin &&
     ('\n'!=*(zPos - 1)
      || ((unsigned)(zEnd - zPos) <= g.delim.n))){
    return 0;
  }else if(0==memcmp(zPos, g.delim.z, g.delim.n)){
    return g.delim.n;
  }else{
    return 0;
  }
}

static void cmpp_t_out_expand(CmppTokenizer * const t,
                              unsigned char const * zFrom,
                              unsigned int n);

static inline int cmpp__isspace(int ch){
  return ' '==ch || '\t'==ch;
}

static inline unsigned cmpp__strlenu(unsigned char const *z, int n){
  return n<0 ? (unsigned)strlen((char const *)z) : (unsigned)n;
}

static inline void cmpp__skip_space_c( unsigned char const **p,
                                       unsigned char const *zEnd ){
  unsigned char const * z = *p;
  while( z<zEnd && cmpp__isspace(*z) ) ++z;
  *p = z;
}

#define ustr_c(X) ((unsigned char const *)X)
//#define ustr_nc(X) ((unsigned char *)X)

/**
   Scan [t->zPos,t->zEnd) for a derective delimiter. Emits any
   non-delimiter output found along the way.

   This updtes t->zPos and t->lineNo as it goes.

   If a delimiter is found, it updates t->token and returns 0.
   On no match returns 0.
*/
static
int CmppTokenizer__delim_search(CmppTokenizer * const t){
  if(!t->zPos) t->zPos = t->zBegin;
  if( t->zPos>=t->zEnd ){
    return 0;
  }
  assert( (t->zPos==t->zBegin || t->zPos[-1]=='\n')
          && "Else we've mismanaged something.");
  char const * const zD = g.delim.z;
  unsigned short const nD = g.delim.n;
  unsigned char const * const zEnd = t->zEnd;
  unsigned char const * zLeft = t->zPos;
  unsigned char const * z = zLeft;

  assert( 0==*zEnd && "Else we'll misinteract with strcspn()" );
  if( *zEnd ){
    fatal("Input must be NUL-terminated.");
    return 0;
  }
#define tflush                                        \
  if(z>zEnd) z=zEnd;                                  \
  if( z>zLeft ) {                                     \
    cmpp_t_out_expand(t, zLeft, (unsigned)(z-zLeft)); \
  } zLeft = z
  while(z < zEnd){
    size_t nNlTotal = 0;
    unsigned char const * zNl;
    size_t nNl2 = strcspn((char const *)z, "\n");
    zNl = (z + nNl2 >= zEnd ? zEnd : z + nNl2);
    if( nNl2 >= CmppArgs_BufSize /* too long */
        //|| '\n'!=(char)*zNl   /* end of input */
        /* ^^^ we have to accept a missing trailing EOL for the
           sake of -e scripts. */
    ){
      /* we'd like to error out here, but only if we know we're
         reading reading a directive line. */
      ++t->lineNo;
      z = zNl + 1;
      tflush;
      continue;
    }
    nNlTotal += nNl2;
    assert( '\n'==*zNl || !*zNl );
    assert( '\n'==*zNl || zNl==zEnd );
    //g_stderr("input: zNl=%d z=<<<%.*s>>>", (int)*zNl, (zNl-z), z);
    unsigned char const * const zBOL = z;
    cmpp__skip_space_c(&z, zNl);
    if( z+nD < zNl && 0==memcmp(z, zD, nD) ){
      /* Found a directive delimiter. */
      if( zBOL!=z ){
        /* Do not emit space from the same line which preceeds a
           delimiter */
        zLeft = z;
      }
      while( zNl>z && zNl<zEnd
             && '\n'==*zNl && '\\'==zNl[-1] ){
        /* Backslash-escaped newline: extend the token
           to consume it all. */
        ++t->lineNo;
        ++zNl;
        nNl2 = strcspn((char const *)zNl, "\n");
        if( !nNl2 ) break;
        nNlTotal += nNl2;
        zNl += nNl2;
      }
      assert( zNl<=zEnd && "Else our input was not NUL-terminated");
      if( nNlTotal >= CmppArgs_BufSize ){
        fatal("Directive line is too long (%u)",
              (unsigned)(zNl-z));
        break;
      }
      tflush;
      t->token.zBegin = z + nD;
      t->token.zEnd = zNl;
      cmpp__skip_space_c(&t->token.zBegin, t->token.zEnd);
      t->token.ttype = TT_Line;
      t->token.lineNo = t->lineNo++;
      t->zPos = t->token.zEnd + 1;
      if( 0 ){
        g_stderr("token=<<%.*s>>", (t->token.zEnd - t->token.zBegin),
                 t->token.zBegin);
      }
      return 1;
    }
    z = zNl+1;
    ++t->lineNo;
    tflush;
    //g_stderr("line #%d no match\n",(int)t->lineNo);
  }
  tflush;
  t->zPos = z;
  return 0;
#undef tflush
}

void cmpp_kvp_parse(cmpp_kvp * p, char const *zKey, int nKey,
                    cmpp_kvp_op_e opPolicy){
  char chEq = 0;
  char opLen = 0;
  *p = cmpp_kvp_empty;
  p->k.z = zKey;
  p->k.n = cmpp_strlen(zKey, nKey);
  switch( opPolicy ){
    case cmpp_kvp_op_none: break;
    case cmpp_kvp_op_eq1:
      chEq = '=';
      opLen = 1;
      break;
    default:
      assert(!"don't use these yet");
      /* todo: ==, !=, <=, <, >, >= */
      chEq = '=';
      opLen = 1;
      break;
  }
  assert( chEq );
  p->op = cmpp_kvp_op_none;
  const char * const zEnd = p->k.z + p->k.n;
  for(const char * zPos = p->k.z ; *zPos && zPos<zEnd ; ++zPos) {
    if( chEq==*zPos ){
      if( cmpp_kvp_op_none==opPolicy ){
        fatal("Illegal operator in key: %s", zKey);
      }
      p->op = cmpp_kvp_op_eq1;
      p->k.n = (unsigned)(zPos - zKey);
      zPos += opLen;
      assert( zPos <= zEnd );
      p->v.z = zPos;
      p->v.n = (unsigned)(zEnd - zPos);
      break;
    }
  }
  cmpp_affirm_legal_key(p->k.z, p->k.n);
}

static void cmpp_t_out_expand(CmppTokenizer * const t,
                              unsigned char const * zFrom,
                              unsigned int n){
  unsigned char const *zLeft = zFrom;
  unsigned char const * const zEnd = zFrom + n;
  unsigned char const *z = AT_OFF==g.flags.atPolicy ? zEnd : zLeft;
  unsigned char const chEol = (unsigned char)'\n';
  int state = 0 /* 0==looking for opening @
                ** 1==looking for closing @ */;
  if( 0 ){
    g_warn("zLeft=%d %c", (int)*zLeft, *zLeft);
  }
#define tflush \
  if(z>zEnd) z=zEnd; \
  if(zLeft<z){ cmpp_t_out(t, zLeft, (z-zLeft)); } zLeft = z
  for( ; z<zEnd; ++z ){
    zLeft = z;
    for( ;z<zEnd; ++z ){
      if( chEol==*z ){
        state = 0;
        continue;
      }
      if( g.delim.chAt==*z ){
        if( 0==state ){
          tflush;
          state = 1;
        }else{ /* process chAt...chAt */
          char *zVal = 0;
          unsigned int nVal = 0;
          assert( 1==state );
          assert( g.delim.chAt==*zLeft );
          assert( zLeft<z );
          if( z==zLeft+1 ){
            tflush;
          }else{
            char const *zKey = (char const*)zLeft+1;
            int const nKey = (z-zLeft-1);
            if( db_define_get(zKey, nKey, &zVal, &nVal) ){
              if( nVal ){
                cmpp_t_out(t, (unsigned char const*)zVal, nVal);
              }else{
                /* Elide it */
              }
              zLeft = z+1/*skip closing g.delim.chAt*/;
              db_free(zVal);
            }else{
              assert( !zVal );
              /* No match. Emit it as-is. */
              switch( g.flags.atPolicy ){
                case AT_RETAIN:
                  tflush;
                  break;
                case AT_ERROR:
                  fatal("Undefined key: %c%.*s%c",
                        g.delim.chAt, nKey, zKey, g.delim.chAt );
                  break;
                case AT_ELIDE:
                  zLeft = z+1;
                  break;
                case AT_invalid:
                case AT_OFF:
                  fatal("Unhandled g.flags.atPolicy #%d!",
                        g.flags.atPolicy);
                  break;
              }
            }
            state = 0;
          }
        }/* process chAt...chAt */
      }/*g.delim.chAt*/
    }/*per-line loop*/
  }/*outer loop*/
  tflush;
#undef tflush
  return;
}

/*
** Scans t to the next keyword line, emitting all input before that
** which is _not_ a keyword line unless it's elided due to being
** inside a block which elides its content. Returns 0 if no keyword
** line was found, in which case the end of the input has been
** reached, else returns a truthy value and sets up t's state for use
** with cmpp_process_keyword(), which should then be called.
*/
static int cmpp_next_keyword_line(CmppTokenizer * const t){
  CmppToken * const tok = &t->token;

  assert(t->zBegin);
  assert(t->zEnd > t->zBegin);
  if(!t->zPos) t->zPos = t->zBegin;
  t->args.pKw = 0;
  t->args.argc = 0;
  *tok = CmppToken_empty;
  if( !CmppTokenizer__delim_search(t) ){
    return 0;
  }
  /* Split t->token into arguments for the line's keyword */
  int i, argc = 0, prevChar = 0;
  const unsigned tokLen = (unsigned)(tok->zEnd - tok->zBegin);
  unsigned char * zKwd;
  unsigned char * zEsc;
  unsigned char * zz;

  assert(TT_Line==tok->ttype);
  g_debug(2,("token @ line %u len=%u [[[%.*s]]]\n",
             tok->lineNo, tokLen, tokLen, tok->zBegin));
  zKwd = &t->args.lineBuf[0];
  memcpy(zKwd, tok->zBegin, tokLen);
  memset(zKwd + tokLen, 0, sizeof(t->args.lineBuf) - tokLen);
  for( zEsc = 0, zz = zKwd; *zz; ++zz ){
    /* Convert backslash-escaped newlines to whitespace */
    switch((int)*zz){
      case (int)'\\':
        if(zEsc) zEsc = 0;
        else zEsc = zz;
        break;
      case (int)'\n':
        assert(zEsc && "Should not have an unescaped newline?");
        if(zEsc==zz-1){
          *zEsc = (unsigned char)' ';
          /* FIXME?: memmove() lnBuf content one byte to the left here
          ** to collapse backslash and newline into a single
          ** byte. Also consider collapsing all leading space on the
          ** next line. (Much later: or just collapse the output as we go,
          ** effectively shrinking the line.) */
        }
        zEsc = 0;
        *zz = (unsigned char)' ';
        break;
      default:
        zEsc = 0;
        break;
    }
  }
  t->args.argv[argc++] = zKwd;
  for( zz = zKwd; *zz; ++zz ){
    if(isspace(*zz)){
      *zz = 0;
      break;
    }
  }
  t->args.pKw = CmppKeyword_search((char const *)zKwd);
  if(!t->args.pKw){
    fatal("Unknown keyword '%s' at line %u\n", (char const *)zKwd,
          tok->lineNo);
  }
  for( ++zz ; *zz && isspace(*zz); ++zz ){}
  if(t->args.pKw->bTokenize){
    for( ; *zz; prevChar = *zz, ++zz ){
      /* Split string into word-shaped tokens.
      ** TODO ?= quoted strings, for the sake of the
      ** #error keyword. */
      if(isspace(*zz)){
        assert(zz!=zKwd && "Leading space was stripped earlier.");
        *zz = 0;
      }else{
        if(argc == (int)CmppArgs_Max){
          fatal("Too many arguments @ line %u: %.*s",
                tok->lineNo, tokLen, tok->zBegin);
        }else if(zz>zKwd && !prevChar){
          t->args.argv[argc++] = zz;
        }
      }
    }
  }else{
    /* Treat rest of line as one token */
    if(*zz) t->args.argv[argc++] = zz;
  }
  tok->ttype = t->args.pKw->ttype;
  if(g.flags.doDebug>1){
    for(i = 0; i < argc; ++i){
      g_debug(0,("line %u arg #%d=%s\n",
                 tok->lineNo, i,
                 (char const *)t->args.argv[i]));
    }
  }
  t->args.argc = argc;
  return 1;
}

/* Internal error reporting helper for cmpp_keyword_f() impls. */
static CMPP_NORETURN void cmpp_kwd__err_(char const *zFile, int line,
                                         CmppKeyword const * pKw,
                                         CmppTokenizer const *t,
                                         char const *zFmt, ...){
  va_list va;
  g_stderr("%s @ %s line %u:",
           pKw->zName, t->zName, t->token.lineNo);
  va_start(va, zFmt);
  g.tok = 0 /* stop fatalv__base() from duplicating the file info */;
  fatalv__base(zFile, line, zFmt, va);
  /* not reached */
  va_end(va);
}
#define cmpp_kwd__err(...) cmpp_kwd__err_(__FILE__,__LINE__, __VA_ARGS__)
#define cmpp_t__err(T,...) cmpp_kwd__err_(__FILE__,__LINE__, (T)->args.pKw, (T), __VA_ARGS__)

/* No-op cmpp_keyword_f() impl. */
static void cmpp_kwd_noop(CmppKeyword const * pKw, CmppTokenizer *t){
  (void)pKw;
  (void)t;
}

/* #error impl. */
static void cmpp_kwd_error(CmppKeyword const * pKw, CmppTokenizer *t){
  if(CT_skip(t)) return;
  else{
    assert(t->args.argc < 3);
    const char *zBegin = t->args.argc>1
      ? (const char *)t->args.argv[1] : 0;
    cmpp_t__err(t, "%s", zBegin ? zBegin : "(no additional info)");
  }
}

/* Impl. for #define, #undef */
static void cmpp_kwd_define(CmppKeyword const * pKw, CmppTokenizer *t){
  if(CT_skip(t)) return;
  if(t->args.argc<2){
    cmpp_kwd__err(pKw, t, "Expecting one or more arguments");
  }else{
    int i = 1;
    for( ; i < t->args.argc; ++i){
      char const * const zArg = (char const *)t->args.argv[i];
      cmpp_affirm_legal_key(zArg, -1);
      if( TT_Define==pKw->ttype ){
        db_define_add( zArg, NULL );
      }else{
        db_define_rm( zArg );
      }
    }
  }
}

static int cmpp_val_matches(char const *zGlob, char const *zRhs){
  return 0==sqlite3_strglob(zGlob, zRhs);
}

typedef int (*cmpp_vcmp_f)(char const *zLhs, char const *zRhs);

/*
** Accepts a key in the form X or X=Y. In the former case, it uses
** db_define_get_bool(kvp->k) to determine its truthiness, else it
** compares the kvp->v part to kvp->k's defined value to determine
** truthiness.
**
** Unless...
**
** If bCheckDefined is true is true then (A) it returns true if the
** value is defined and (B) fails fatally if given an X=Y-format key.
**
** Returns true if zKey evals to true, else false.
*/
//static
int cmpp_kvp_truth(CmppKeyword const * const pKw,
                   CmppTokenizer const * const t,
                   cmpp_kvp const * const kvp,
                   int bCheckDefined){
  int buul = 0;
  if( kvp->v.z ){
    if( bCheckDefined ){
      cmpp_kwd__err(pKw, t, "Value part is not legal for "
                    "is-defined checks: %.s",
                    kvp->k.n, kvp->k.z);
    }
    char * zVal = 0;
    unsigned int nVal = 0;
    buul = db_define_get(kvp->k.z, (int)kvp->k.n, &zVal, &nVal);
      //g_debug(0,("checking key[%.*s]=%.*s\n", (zEq-zKey), zKey, nVal, zVal));
    if( kvp->v.n && nVal ){
      /* FIXME? do this with a query */
      /*g_debug(0,("if get-define [%.*s]=[%.*s] zValPart=%s\n",
        (zEq-zKey), zKey,
        nVal, zVal, zValPart));*/
      buul = cmpp_val_matches(kvp->v.z, zVal);
      //g_debug(0,("buul=%d\n", buul));
    }else{
      assert( 0==kvp->v.n || 0==nVal );
      buul = kvp->v.n == nVal;
    }
    db_free(zVal);
  }else{
    if( bCheckDefined ){
      buul = db_define_has(kvp->k.z, kvp->k.n);
    }else{
      buul = db_define_get_bool(kvp->k.z, kvp->k.n);
    }
  }
  return buul;
}

#if 0
/*
** A thin proxy for cmpp_kvp_truth().
*/
static int cmpp_key_truth(CmppKeyword const * pKw,
                          CmppTokenizer const * t,
                          char const *zKey, int bCheckDefined){
  cmpp_kvp kvp = cmpp_kvp_empty;
  cmpp_kvp_parse(&kvp, zKey, -1, cmpp_kvp_op_eq1);
  return cmpp_kvp_truth(pKw, t, &kvp, bCheckDefined);
}
#endif

//static
cmpp_kvp_op_e cmpp_t_is_op(CmppTokenizer const * t, int arg){
  if( t->args.argc > arg ){
    char const * const z = (char const *)t->args.argv[arg];
#define E(N,S) if( strcmp(S,z) ) return cmpp_kvp_op_ ## N; else
  cmpp_kvp_op_map(E)
#undef E
    if(0) {}
  }
  return cmpp_kvp_op_none;
}

/*
** A single part of an #if-type expression. They are parsed from
** CmppTokenizer::args in this form:
**
**  not* defined{0,1} key[=[value]]
*/
struct CmppExprDef {
  /* The key part of the input. */
  cmpp_kvp kvp;
  struct {
    int ndx;
    int next;
  } arg;
  CmppTokenizer const * tizer;
  /* Set to 0 or 1 depending how many "not" are parsed. */
  unsigned char bNegated;
  /* Set to 1 if "defined" is parsed. */
  unsigned char bCheckDefined;
};
typedef struct CmppExprDef CmppExprDef;
#define CmppExprDef_empty_m {cmpp_kvp_empty_m,{0,0},0,0,0}
static const CmppExprDef CmppExprDef_empty = CmppExprDef_empty_m;

/*
** Evaluate cep to true or false and return that value:
**
** If cep->bCheckDefined, return the result of db_define_has().
**
** Else if cep->kvp.v.z is not NULL then fetch the define's value
** and return the result of cmpp_val_matches(cep->kvp.v.z,thatValue).
**
** Else return the result of db_define_get_bool().
**
** The returned result accounts for cep->bNegated.
*/
static int CmppExprDef_eval(CmppExprDef const * cep){
  int buul = 0;

  if( cep->bCheckDefined ){
    assert( !cep->kvp.v.n );
    buul = db_define_has(cep->kvp.k.z, (int)cep->kvp.k.n);
  }else if( cep->kvp.v.z ){
    unsigned nVal = 0;
    char * zVal = 0;
    buul = db_define_get(cep->kvp.k.z, cep->kvp.k.n, &zVal, &nVal);
    if( nVal ){
      buul = cmpp_val_matches(cep->kvp.v.z, zVal);
    }
    db_free(zVal);
  }else{
    buul = db_define_get_bool(cep->kvp.k.z, cep->kvp.k.n);
  }
  return cep->bNegated ? !buul : buul;
}

/*
** Expects t->args, starting at t->args.argv[startArg], to parse to
** one CmmpExprDef. It clears cep and repopulates it with info about
** the parse. Fails fatally on a parse error.
**
** Returns true if it reads one, false if it doesn't, and fails fatally
** if what it tries to parse is not empty but is not a CmppExprDef.
**
** Specifically, it parses:
**
**   not+ defined? Word[=value]
**
*/
static int CmppExprDef_read_one(CmppKeyword const * pKw,
                                CmppTokenizer const * t,
                                int startArg, CmppExprDef * cep){
  char const *zKey = 0;
  *cep = CmppExprDef_empty;
  cep->arg.ndx = startArg;
  assert( t->args.pKw );
  assert( t->args.pKw==pKw );
  cep->tizer = t;
  for(int i = startArg; !zKey && i<t->args.argc; ++i ){
    char const * z = (char const *)t->args.argv[i];
    if( 0==strcmp(z, "not") ){
      cep->bNegated = !cep->bNegated;
    }else if( 0==strcmp(z,"defined") ){
      if( cep->bCheckDefined ){
        cmpp_kwd__err(pKw, t,
                      "Cannot use 'defined' more than once");
      }
      cep->bCheckDefined = 1;
    }else{
      assert( !zKey );
      cmpp_kvp_parse(&cep->kvp, z, -1, cmpp_kvp_op_eq1);
      if( cep->bCheckDefined && cep->kvp.v.z ){
        cmpp_kwd__err(pKw, t, "Cannot use X=Y keys with 'defined'");
        cep->arg.next = ++i;
      }
      return 1;
    }
  }
  return 0;
}

/*
** Evals pStart and then proceeds to process any remaining arguments
** in t->args as RHS expressions. Returns the result of the expression
** as a bool.
**
** Specifically, it parses:
**
**   and|or CmppExprDef
**
** Where CmppExprDef is the result of CmppExprDef_read_one().
*/
static int CmppExprDef_parse_cond(CmppKeyword const *pKw,
                                  CmppTokenizer *t,
                                  CmppExprDef const * pStart){
  enum { Op_none = 0, Op_And, Op_Or };
  int lhs = CmppExprDef_eval(pStart);
  int op = Op_none;
  int i = pStart->arg.next;
  for( ; i < t->args.argc; ++i ){
    CmppExprDef eNext = CmppExprDef_empty;
    char const *z = (char const *)t->args.argv[i];
    if( 0==strcmp("and",z) ){
      if( Op_none!=op ) goto multiple_ops;
      op = Op_And;
      continue;
    }else if( 0==strcmp("or",z) ){
      if( Op_none!=op ) goto multiple_ops;
      op = Op_Or;
      continue;
    }else if( !CmppExprDef_read_one(pKw, t, i, &eNext) ){
      if( Op_none!=op ){
        cmpp_t__err(t, "Stray operator: %s",z);
      }
    }
    assert( eNext.kvp.k.z );
    int const rhs = CmppExprDef_eval(&eNext);
    switch( op ){
      case Op_none: break;
      case Op_And: lhs = lhs && rhs; break;
      case Op_Or:  lhs = lhs || rhs; break;
      default:
        assert(!"cannot happen");
        fatal("this cannot happen");
    }
    op = Op_none;
  }
  if( Op_none!=op ){
    cmpp_t__err(t, "Extra operator at end of expression");
  }else if( i < t->args.argc ){
    assert(!"cannot happen");
    cmpp_kwd__err(t->args.pKw, t, "Unhandled extra arguments");
  }else{
    return lhs;
  }
  assert(!"not reached");
multiple_ops:
  cmpp_t__err(t,"Cannot have multiple operators");
  return 0 /* not reached */;
}

/* Impl. for #if, #elif, #assert. */
static void cmpp_kwd_if(CmppKeyword const * pKw, CmppTokenizer *t){
  CmppParseState tmpState = TS_Start;
  CmppExprDef cep = CmppExprDef_empty;
  //int buul = 0;
  assert( TT_If==pKw->ttype
          || TT_Elif==pKw->ttype
          || TT_Assert==pKw->ttype);
  if(t->args.argc<2){
    cmpp_kwd__err(pKw, t, "Expecting an argument");
  }
  CmppExprDef_read_one(pKw, t, 1, &cep);
  if( !cep.kvp.k.z ){
    cmpp_kwd__err(pKw, t, "Missing key argument");
  }
  /*g_debug(0,("%s %s level %u pstate=%d bNot=%d bCheckDefined=%d\n",
             pKw->zName, zKey, t->level.ndx, (int)CT_pstate(t),
             bNot, bCheckDefined));*/
  switch(pKw->ttype){
    case TT_Assert:
      break;
    case TT_Elif:
      switch(CT_pstate(t)){
        case TS_If: break;
        case TS_IfPassed: CT_level(t).flags |= CmppLevel_F_ELIDE; return;
        default:
          cmpp_kwd__err(pKw, t, "'%s' used out of context",
                        pKw->zName);
      }
      break;
    case TT_If:
      CmppLevel_push(t);
      break;
    default:
      assert(!"cannot happen");
      cmpp_kwd__err(pKw, t, "Unexpected keyword token type");
      break;
  }
  if( CmppExprDef_parse_cond( pKw, t, &cep ) ){
    CT_pstate(t) = tmpState = TS_IfPassed;
    CT_skipLevel(t) = 0;
  }else{
    if( TT_Assert==pKw->ttype ){
      cmpp_kwd__err(pKw, t, "Assertion failed: %s",
                    /* fixme: emit the whole line. We don't have it
                       handy in a readily-printable form. */
                    cep.kvp.k.z);
    }
    CT_pstate(t) = TS_If /* also for TT_Elif */;
    CT_skipLevel(t) = 1;
    g_debug(3,("setting CT_skipLevel = 1 @ level %d\n", t->level.ndx));
  }
  if( TT_If==pKw->ttype ){
    unsigned const lvlIf = t->level.ndx;
    CmppToken const lvlToken = CT_level(t).token;
    while(cmpp_next_keyword_line(t)){
      cmpp_process_keyword(t);
      if(lvlIf > t->level.ndx){
        assert(TT_Endif == t->token.ttype);
        break;
      }
#if 0
      if(TS_IfPassed==tmpState){
        tmpState = TS_Start;
        t->level.stack[lvlIf].flags |= CmppLevel_F_ELIDE;
        g_debug(1,("Setting ELIDE for TS_IfPassed @ lv %d (lvlIf=%d)\n", t->level.ndx, lvlIf));
      }
#endif
    }
    if(lvlIf <= t->level.ndx){
      cmpp_kwd__err(pKw, t,
                    "Input ended inside an unterminated %sif "
                    "opened at [%s] line %u",
                    g.delim.z, t->zName, lvlToken.lineNo);
    }
  }
}

/* Impl. for #else. */
static void cmpp_kwd_else(CmppKeyword const * pKw, CmppTokenizer *t){
  if(t->args.argc>1){
    cmpp_kwd__err(pKw, t, "Expecting no arguments");
  }
  switch(CT_pstate(t)){
    case TS_IfPassed: CT_skipLevel(t) = 1; break;
    case TS_If: CT_skipLevel(t) = 0; break;
    default:
      cmpp_kwd__err(pKw, t, "'%s' with no matching 'if'",
                    pKw->zName);
  }
  /*g_debug(0,("else flags=0x%02x skipLevel=%u\n",
    CT_level(t).flags, CT_level(t).skipLevel));*/
  CT_pstate(t) = TS_Else;
}

/* Impl. for #endif. */
static void cmpp_kwd_endif(CmppKeyword const * pKw, CmppTokenizer *t){
  /* Maintenance reminder: we ignore all arguments after the endif
  ** to allow for constructs like:
  **
  ** #endif // foo
  **
  ** in a manner which does not require a specific comment style */
  switch(CT_pstate(t)){
    case TS_Else:
    case TS_If:
    case TS_IfPassed:
      break;
    default:
      cmpp_kwd__err(pKw, t, "'%s' with no matching 'if'",
                    pKw->zName);
  }
  CmppLevel_pop(t);
}

/* Impl. for #include. */
static void cmpp_kwd_include(CmppKeyword const * pKw, CmppTokenizer *t){
  char const * zFile;
  char * zResolved;
  int bRaw = 0 /* -raw flag */;
  if(CT_skip(t)) return;
  else if(t->args.argc<2 || t->args.argc>3){
    cmpp_kwd__err(pKw, t, "Expected args: ?-raw? filename");
  }
  if(t->args.argc==2){
    zFile = (const char *)t->args.argv[1];
  }else{
    if( 0==strcmp("-raw", (char*)t->args.argv[1]) ){
      bRaw = 1;
    }else{
      cmpp_kwd__err(pKw, t, "Unhandled argument: %s",
                    t->args.argv[1]);
    }
    zFile = (const char *)t->args.argv[2];
  }
  if(!bRaw && db_including_has(zFile)){
    /* Note that different spellings of the same filename
    ** will elude this check, but that seems okay, as different
    ** spellings means that we're not re-running the exact same
    ** invocation. We might want some other form of multi-include
    ** protection, rather than this, however. There may well be
    ** sensible uses for recursion. */
    cmpp_t__err(t, "Recursive include of file: %s", zFile);
  }
  zResolved = db_include_search(zFile);
  if(zResolved){
    if( bRaw ) db_including_add(zFile, t->zName, t->token.lineNo);
    cmpp_process_file(zResolved, bRaw);
    if( bRaw ) db_include_rm(zFile);
    db_free(zResolved);
  }else{
    cmpp_t__err(t, "file not found: %s", zFile);
  }
}

static void cmpp_dump_defines( FILE * fp, int bIndent ){
  sqlite3_stmt * const q = g_stmt(GStmt_defSelAll);
  while( SQLITE_ROW==sqlite3_step(q) ){
    unsigned char const * zK = sqlite3_column_text(q, 0);
    unsigned char const * zV = sqlite3_column_text(q, 1);
    int const nK = sqlite3_column_bytes(q, 0);
    int const nV = sqlite3_column_bytes(q, 1);
    fprintf(fp, "%s%.*s = %.*s\n",
            bIndent ? "\t" : "", nK, zK, nV, zV);
  }
  g_stmt_reset(q);
}

/* Impl. for #pragma. */
static void cmpp_kwd_pragma(CmppKeyword const * pKw, CmppTokenizer *t){
  const char * zArg;
  if(CT_skip(t)) return;
  else if(t->args.argc<2){
    cmpp_kwd__err(pKw, t, "Expecting an argument");
  }
  zArg = (const char *)t->args.argv[1];
#define M(X) 0==strcmp(zArg,X)
  if(M("defines")){
    cmpp_dump_defines(stderr, 1);
  }
  else if(M("chomp-F")){
    g.flags.chompF = 1;
  }else if(M("no-chomp-F")){
    g.flags.chompF = 0;
  }
#if 0
  /* now done by cmpp_kwd_at_policy() */
  else if(M("@")){
    if(t->args.argc>2){
      g.flags.atPolicy =
        AtPolicy_fromStr((char const *)t->args.argv[2], 1);
    }else{
      g.flags.atPolicy = AT_DEFAULT;
    }
  }else if(M("no-@")){
    g.flags.atPolicy = AT_OFF;
  }
#endif
  else{
    cmpp_kwd__err(pKw, t, "Unknown pragma: %s", zArg);
  }
#undef M
}

static void db_step_reset(sqlite3_stmt * const q, char const * zErrTip){
  db_affirm_rc(sqlite3_step(q), zErrTip);
  g_stmt_reset(q);
}

static void cmpp_sp_begin(CmppTokenizer * const t){
  db_step_reset(g_stmt(GStmt_spBegin), "Starting savepoint");
  ++t->nSavepoint;
}

static void cmpp_sp_rollback(CmppTokenizer * const t){
  if( !t->nSavepoint ){
    cmpp_t__err(t, "Cannot roll back: no active savepoint");
  }
  db_step_reset(g_stmt(GStmt_spRollback),
                "Rolling back savepoint");
  db_step_reset(g_stmt(GStmt_spRelease),
                "Releasing rolled-back savepoint");
  --t->nSavepoint;
}

static void cmpp_sp_commit(CmppTokenizer * const t){
  if( !t->nSavepoint ){
    cmpp_t__err(t, "Cannot commit: no active savepoint");
  }
  db_step_reset(g_stmt(GStmt_spRelease), "Rolling back savepoint");
  --t->nSavepoint;
}

void CmppTokenizer_cleanup(CmppTokenizer * const t){
  while( t->nSavepoint ){
    cmpp_sp_rollback(t);
  }
}

/* Impl. for #savepoint. */
static void cmpp_kwd_savepoint(CmppKeyword const * pKw, CmppTokenizer *t){
  const char * zArg;
  if(CT_skip(t)) return;
  else if(t->args.argc!=2){
    cmpp_kwd__err(pKw, t, "Expecting one argument");
  }
  zArg = (const char *)t->args.argv[1];
#define M(X) 0==strcmp(zArg,X)
  if(M("begin")){
    cmpp_sp_begin(t);
  }else if(M("rollback")){
    cmpp_sp_rollback(t);
  }else if(M("commit")){
    cmpp_sp_commit(t);
  }else{
    cmpp_kwd__err(pKw, t, "Unknown savepoint option: %s", zArg);
  }
#undef SP_NAME
#undef M
}

/* #stder impl. */
static void cmpp_kwd_stderr(CmppKeyword const * pKw, CmppTokenizer *t){
  if(CT_skip(t)) return;
  else{
    const char *zBegin = t->args.argc>1
      ? (const char *)t->args.argv[1] : 0;
    if(zBegin){
      g_stderr("%s:%u: %s\n", t->zName, t->token.lineNo, zBegin);
    }else{
      g_stderr("%s:%u: (no %.*s%s argument)\n",
               t->zName, t->token.lineNo,
               g.delim.n, g.delim.z, pKw->zName);
    }
  }
}

/* Impl. for the @ policy. */
static void cmpp_kwd_at_policy(CmppKeyword const * pKw, CmppTokenizer *t){
  if(CT_skip(t)) return;
  else if(t->args.argc<2){
    g.flags.atPolicy = AT_DEFAULT;
  }else{
    g.flags.atPolicy = AtPolicy_fromStr((char const*)t->args.argv[1], 1);
  }
}


#if 0
/* Impl. for dummy placeholder. */
static void cmpp_kwd_todo(CmppKeyword const * pKw, CmppTokenizer *t){
  (void)t;
  g_debug(0,("TODO: keyword handler for %s\n", pKw->zName));
}
#endif

CmppKeyword aKeywords[] = {
/* Keep these sorted by zName */
#define S(NAME) DStrings.NAME.z, DStrings.NAME.n
  {S(Comment), 0, TT_Comment, cmpp_kwd_noop},
  {S(AtPolicy), 1, TT_AtPolicy, cmpp_kwd_at_policy},
  {S(Assert),1, TT_Assert, cmpp_kwd_if},
  {S(Define), 1, TT_Define, cmpp_kwd_define},
  {S(Elif), 1, TT_Elif, cmpp_kwd_if},
  {S(Else), 1, TT_Else, cmpp_kwd_else},
  {S(Endif), 0, TT_Endif, cmpp_kwd_endif},
  {S(Error), 0, TT_Error, cmpp_kwd_error},
  {S(If), 1, TT_If, cmpp_kwd_if},
  {S(Include), 1, TT_Include, cmpp_kwd_include},
  {S(Pragma), 1, TT_Pragma, cmpp_kwd_pragma},
  {S(Savepoint), 1, TT_Savepoint, cmpp_kwd_savepoint},
  {S(Stderr), 0, TT_Stderr, cmpp_kwd_stderr},
  {S(Undef), 1, TT_Undef, cmpp_kwd_define},
#undef S
  {0,0,TT_Invalid, 0}
};

static int cmpp_CmppKeyword(const void *p1, const void *p2){
  char const * zName = (const char *)p1;
  CmppKeyword const * kw = (CmppKeyword const *)p2;
  return strcmp(zName, kw->zName);
}

CmppKeyword const * CmppKeyword_search(const char *zName){
  return (CmppKeyword const *)bsearch(zName, &aKeywords[0],
                                      sizeof(aKeywords)/sizeof(aKeywords[0]) - 1,
                                      sizeof(aKeywords[0]),
                                      cmpp_CmppKeyword);
}

void cmpp_process_keyword(CmppTokenizer * const t){
  assert(t->args.pKw);
  assert(t->args.argc);
  t->args.pKw->xCall(t->args.pKw, t);
  t->args.pKw = 0;
  t->args.argc = 0;
}

void cmpp_process_string(const char * zName,
                        unsigned char const * zIn,
                        int nIn){
  nIn = cmpp__strlenu(zIn, nIn);
  if( !nIn ) return;
  CmppTokenizer const * const oldTok = g.tok;
  CmppTokenizer ct = CmppTokenizer_empty;
  ct.zName = zName;
  ct.zBegin = zIn;
  ct.zEnd = zIn + nIn;
  while(cmpp_next_keyword_line(&ct)){
    cmpp_process_keyword(&ct);
  }
  if(0!=ct.level.ndx){
    CmppLevel const * const lv = CmppLevel_get(&ct);
    fatal("Input ended inside an unterminated nested construct "
          "opened at [%s] line %u", zName, lv->token.lineNo);
  }
  CmppTokenizer_cleanup(&ct);
  g.tok = oldTok;
}

void cmpp_process_file(const char * zName, int bRaw){
  FileWrapper fw = FileWrapper_empty;
  FileWrapper_open(&fw, zName, "r");
  g_FileWrapper_link(&fw);
  FileWrapper_slurp(&fw);
  g_debug(1,("Read %u byte(s) from [%s]\n", fw.nContent, fw.zName));
  if( fw.zContent ){
    if( bRaw ){
      FileWrapper fw = FileWrapper_empty;
      FileWrapper_open(&fw, zName, "rb");
      g_FileWrapper_link(&fw);
      FileWrapper_slurp(&fw);
      if( 1!=fwrite(fw.zContent, fw.nContent, 1, g.out.pFile) ){
        fatal("fwrite() failed with errno %d\n", errno);
      }
      g_FileWrapper_close(&fw);
    }else{
      cmpp_process_string(zName, fw.zContent, fw.nContent);
    }
  }
  g_FileWrapper_close(&fw);
}


void fatalv__base(char const *zFile, int line,
                  char const *zFmt, va_list va){
  FILE * const fp = stderr;
  fflush(stdout);
  fputc('\n', fp);
  if( g.flags.doDebug ){
    fprintf(fp, "%s: ", g.zArgv0);
    if( zFile ){
      fprintf(fp, "%s:%d ",zFile, line);
    }
  }
  if( g.tok ){
    fprintf(fp,"@%s:%d: ",
            (g.tok->zName && 0==strcmp("-",g.tok->zName))
            ? "<stdin>"
            : g.tok->zName,
            g.tok->lineNo);
  }
  if(zFmt && *zFmt){
    vfprintf(fp, zFmt, va);
  }
  fputc('\n', fp);
  fflush(fp);
  exit(1);
}

void fatal__base(char const *zFile, int line,
                 char const *zFmt, ...){
  va_list va;
  va_start(va, zFmt);
  fatalv__base(zFile, line, zFmt, va);
  va_end(va);
}

#undef CT_level
#undef CT_pstate
#undef CT_skipLevel
#undef CT_skip
#undef CLvl_skip

static void usage(int isErr){
  FILE * const fOut = isErr ? stderr : stdout;
  fprintf(fOut, "Usage: %s [flags] [infile...]\n", g.zArgv0);
  fprintf(fOut,
          "Flags and filenames may be in any order and "
          "they are processed in that order.\n"
          "\nFlags:\n");
#define GAP "     "
#define arg(F,D) fprintf(fOut,"\n  %s\n" GAP "%s\n",F, D)
  arg("-o|--outfile FILE","Send output to FILE (default=- (stdout)).\n"
      GAP "Because arguments are processed in order, this should\n"
      GAP "normally be given before -f.");
  arg("-f|--file FILE","Process FILE (default=- (stdin)).\n"
      GAP "All non-flag arguments are assumed to be the input files.");
  arg("-DXYZ[=value]","Define XYZ to the given value (default=1).");
  arg("-UXYZ","Undefine all defines matching glob XYZ.");
  arg("-IXYZ","Add dir XYZ to the " CMPP_DEFAULT_DELIM "include path.");
  arg("-FXYZ=filename",
      "Define XYZ to the raw contents of the given file.\n"
      GAP "The file is not processed as by " CMPP_DEFAULT_DELIM"include\n"
      GAP "Maybe it should be. Or maybe we need a new flag for that.");
  arg("-d|--delimiter VALUE", "Set keyword delimiter to VALUE "
      "(default=" CMPP_DEFAULT_DELIM ").");
  arg("--@policy retain|elide|error|off",
      "Specifies how to handle @tokens@ (default=off).\n"
      GAP "off    = do not look for @tokens@\n"
      GAP "retain = parse @tokens@ and retain any undefined ones\n"
      GAP "elide  = parse @tokens@ and elide any undefined ones\n"
      GAP "error  = parse @tokens@ and error out for any undefined ones"
  );
  arg("-@", "Equivalent to --@policy=error.");
  arg("-no-@", "Equivalent to --@policy=off (the default).");
  arg("--sql-trace", "Send a trace of all SQL to stderr.");
  arg("--sql-trace-x",
      "Like --sql-trace but expand all bound values in the SQL.");
  arg("--no-sql-trace", "Disable SQL tracing (default).");
  arg("--chomp-F", "One trailing newline is trimmed from files "
      "read via -FXYZ=filename.");
  arg("--no-chomp-F", "Disable --chomp-F (default).");
#undef arg
#undef GAP
  fputs("\nFlags which require a value accept either "
        "--flag=value or --flag value.\n\n",fOut);
}

/*
** Expects that *ndx points to the current argv entry and that it is a
** flag which expects a value. This function checks for --flag=val and
** (--flag val) forms. If a value is found then *ndx is adjusted (if
** needed) to point to the next argument after the value and *zVal is
** pointed to the value. If no value is found then it fails fatally.
*/
static void get_flag_val(int argc, char const * const * argv, int * ndx,
                         char const **zVal){
  char const * zEq = strchr(argv[*ndx], '=');
  if( zEq ){
    *zVal = zEq+1;
    return;
  }
  if(*ndx+1>=argc){
    fatal("Missing value for flag '%s'", argv[*ndx]);
  }
  *zVal = argv[++*ndx];
}

static int arg_is_flag( char const *zFlag, char const *zArg,
                        char const **zValIfEqX ){
  *zValIfEqX = 0;
  if( 0==strcmp(zFlag, zArg) ) return 1;
  char const * z = strchr(zArg,'=');
  if( z && z>zArg ){
    /* compare the part before the '=' */
    if( 0==strncmp(zFlag, zArg, z-zArg) ){
      if( !zFlag[z-zArg] ){
        *zValIfEqX = z+1;
        return 1;
      }
      /* Else it was a prefix match. */
    }
  }
  return 0;
}

static void define_argv(int argc, char const * const * argv){
  sqlite3_str * const s = sqlite3_str_new(g.db);
  sqlite3_str_append(s, "c-pp::argv=", 11);
  for( int i = 0; i < argc; ++i ){
    if( i ) sqlite3_str_appendchar(s, 1, ' ');
    sqlite3_str_appendf(s, "%s", argv[i]);
  }
  char * const z = sqlite3_str_finish(s);
  assert(z);
  if(z){
    db_define_add(z, NULL);
    sqlite3_free(z);
  }
}

int main(int argc, char const * const * argv){
  int rc = 0;
  int inclCount = 0;
  int nFile = 0;
  int ndxTrace = 0;
  int expandMode = 0;
  char const * zVal = 0;
#define ARGVAL if( !zVal ) get_flag_val(argc, argv, &i, &zVal)
#define M(X) arg_is_flag(X, zArg, &zVal)
#define ISFLAG(X) else if(M(X))
#define ISFLAG2(X,Y) else if(M(X) || M(Y))
#define NOVAL if( zVal ) fatal("Unexpected value for %s", zArg)
#define g_out_open \
  if(!g.out.pFile) FileWrapper_open(&g.out, "-", "w");    \
  if(!inclCount){ db_include_dir_add("."); ++inclCount; } (void)0

  g.zArgv0 = argv[0];
#define DOIT if(doIt)
  for(int doIt = 0; doIt<2; ++doIt){
    /**
       Loop through the flags twice. The first time we just validate
       and look for --help/-?. The second time we process the flags.
       This approach allows us to easily chain multiple files and
       flags:

       ./c-pp -Dfoo -o foo x.y -Ufoo -Dbar -o bar x.y
    */
    DOIT{
      atexit(cmpp_atexit);
      if( 1==ndxTrace ){
        /* Ensure that we start with tracing in the early stage if
           --sql-trace is the first arg, in order to log schema
           setup. */
        g.sqlTrace.pFile = stderr;
        g.sqlTrace.expandSql = expandMode;
      }
      cmpp_initdb();
      define_argv(argc, argv);
    }
    for(int i = 1; i < argc; ++i){
      int negate = 0;
      char const * zArg = argv[i];
      //g_stderr("i=%d zArg=%s\n", i, zArg);
      zVal = 0;
      while('-'==*zArg) ++zArg;
      if(zArg==argv[i]/*not a flag*/){
        zVal = zArg;
        goto do_infile;
      }
      if( 0==strncmp(zArg,"no-",3) ){
        zArg += 3;
        negate = 1;
      }
      ISFLAG2("?","help"){
        NOVAL;
        usage(0);
        goto end;
      }else if('D'==*zArg){
        ++zArg;
        if(!*zArg) fatal("Missing key for -D");
        DOIT {
          db_define_add(zArg, 0);
        }
      }else if('F'==*zArg){
        ++zArg;
        if(!*zArg) fatal("Missing key for -F");
        DOIT {
          db_define_add_file(zArg);
        }
      }else if('U'==*zArg){
        ++zArg;
        if(!*zArg) fatal("Missing key for -U");
        DOIT {
          db_define_rm(zArg);
        }
      }else if('I'==*zArg){
        ++zArg;
        if(!*zArg) fatal("Missing directory for -I");
        DOIT {
          db_include_dir_add(zArg);
          ++inclCount;
        }
      }
      ISFLAG2("o","outfile"){
        ARGVAL;
        DOIT {
          FileWrapper_open(&g.out, zVal, "w");
        }
      }
      ISFLAG2("f","file"){
        ARGVAL;
      do_infile:
        DOIT {
          ++nFile;
          g_out_open;
          cmpp_process_file(zVal, 0);
        }
      }
      ISFLAG("e"){
        ARGVAL;
        DOIT {
          ++nFile;
          g_out_open;
          cmpp_process_string("-e script", ustr_c(zVal), -1);
        }
      }
      ISFLAG("@"){
        NOVAL;
        DOIT {
          assert( AT_DEFAULT!=AT_OFF );
          g.flags.atPolicy = negate ? AT_OFF : AT_DEFAULT;
        }
      }
      ISFLAG("@policy"){
        AtPolicy aup;
        ARGVAL;
        aup = AtPolicy_fromStr(zVal, 1);
        DOIT {
          g.flags.atPolicy = aup;
        }
      }
      ISFLAG("debug"){
        NOVAL;
        g.flags.doDebug += negate ? -1 : 1;
      }
      ISFLAG("sql-trace"){
        NOVAL;
        /* Needs to be set before the start of the second pass, when
           the db is inited. */
        g.sqlTrace.expandSql = 0;
        DOIT {
          g.sqlTrace.pFile = negate ? (FILE*)0 : stderr;
        }else if( !ndxTrace && !negate ){
          ndxTrace = i;
          expandMode = 0;
        }
      }
      ISFLAG("sql-trace-x"){
        NOVAL;
        g.sqlTrace.expandSql = 1;
        DOIT {
          g.sqlTrace.pFile = negate ? (FILE*)0 : stderr;
        }else if( !ndxTrace && !negate ){
          ndxTrace = i;
          expandMode = 1;
        }
      }
      ISFLAG("chomp-F"){
        NOVAL;
        DOIT g.flags.chompF = !negate;
      }
      ISFLAG2("d","delimiter"){
        ARGVAL;
        if( !doIt ){
          g.delim.z = zVal;
          g.delim.n = (unsigned short)strlen(zVal);
          if(!g.delim.n) fatal("Keyword delimiter may not be empty.");
        }
      }
      ISFLAG2("dd", "dump-defines"){
        DOIT {
          FILE * const fp = stderr;
          fprintf(fp, "All %sdefine entries:\n", g.delim.z);
          cmpp_dump_defines(fp, 1);
        }
      }
      else{
        fatal("Unhandled flag: %s", argv[i]);
      }
    }
    DOIT {
      if(!nFile){
        if(!g.out.zName) g.out.zName = "-";
        if(!inclCount){
          db_include_dir_add(".");
          ++inclCount;
        }
        FileWrapper_open(&g.out, g.out.zName, "w");
        cmpp_process_file("-", 0);
      }
    }
  }
  end:
  g_cleanup(1);
  return rc ? EXIT_FAILURE : EXIT_SUCCESS;
}