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dnl Copyright (C) 2005, 2007, 2009-2025 Free Software Foundation, Inc. |
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dnl This file is free software; the Free Software Foundation |
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dnl gives unlimited permission to copy and/or distribute it, |
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dnl with or without modifications, as long as this notice is preserved. |
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dnl This file is offered as-is, without any warranty. |
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dnl Written by Oskar Liljeblad. |
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AC_DEFUN([gl_BYTESWAP], |
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[ |
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dnl Prerequisites of lib/byteswap.in.h. |
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AC_CHECK_HEADERS_ONCE([byteswap.h]) |
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if test $ac_cv_header_byteswap_h = yes; then |
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AC_CACHE_CHECK([for working bswap_16, bswap_32, bswap_64], |
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[gl_cv_header_working_byteswap_h], |
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[gl_cv_header_working_byteswap_h=no |
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dnl Check that floating point arguments work. |
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dnl This also checks C libraries with implementations like |
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dnl '#define bswap_16(x) (((x) >> 8 & 0xff) | (((x) & 0xff) << 8))' |
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dnl that mistakenly evaluate their arguments multiple times. |
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AC_COMPILE_IFELSE( |
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[AC_LANG_PROGRAM( |
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[[ |
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]], |
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[[int value_16 = bswap_16 (0.0); |
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int value_32 = bswap_32 (0.0); |
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int value_64 = bswap_64 (0.0); |
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return !(value_16 + value_32 + value_64); |
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]]) |
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], |
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[gl_cv_header_working_byteswap_h=yes], |
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[gl_cv_header_working_byteswap_h=no]) |
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]) |
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fi |
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if test "$gl_cv_header_working_byteswap_h" = yes; then |
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GL_GENERATE_BYTESWAP_H=false |
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else |
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GL_GENERATE_BYTESWAP_H=true |
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fi |
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]) |
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