emacs/m4/endian_h.m4

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# endian_h.m4
# serial 4
dnl Copyright 2024 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.
dnl A placeholder for <endian.h>, for platforms that have issues.
AC_DEFUN_ONCE([gl_ENDIAN_H],
[
AC_REQUIRE([gl_BIGENDIAN])
AC_CHECK_HEADERS_ONCE([endian.h])
gl_CHECK_NEXT_HEADERS([endian.h])
if test $ac_cv_header_endian_h = yes; then
HAVE_ENDIAN_H=1
dnl Check if endian.h defines uint16_t, uint32_t, and uint64_t.
AC_CACHE_CHECK([if endian.h defines stdint types],
[gl_cv_header_endian_h_stdint_types],
[AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[[#include <endian.h>
]],
[[uint16_t t1 = 0;
uint32_t t2 = 0;
uint64_t t3 = 0;
return !(t1 + t2 + t3);
]])],
[gl_cv_header_endian_h_stdint_types=yes],
[gl_cv_header_endian_h_stdint_types=no])
])
AC_CACHE_CHECK([if endian.h defines functions and macros],
[gl_cv_header_working_endian_h],
[gl_cv_header_working_endian_h=no
AC_COMPILE_IFELSE(
[AC_LANG_PROGRAM(
[[
#include <endian.h>
]],
[[
#if LITTLE_ENDIAN == BIG_ENDIAN
# error "Endian macros not unique."
#endif
#if BYTE_ORDER != LITTLE_ENDIAN && BYTE_ORDER != BIG_ENDIAN
# error "Byte order not defined."
#endif
/* Big endian to host. */
int value16_1 = be16toh (0.0);
int value32_1 = be32toh (0.0);
int value64_1 = be64toh (0.0);
/* Host to big endian. */
int value16_2 = htobe16 (0.0);
int value32_2 = htobe32 (0.0);
int value64_2 = htobe64 (0.0);
/* Little endian to host. */
int value16_3 = le16toh (0.0);
int value32_3 = le32toh (0.0);
int value64_3 = le64toh (0.0);
/* Host to little endian. */
int value16_4 = htole16 (0.0);
int value32_4 = htole32 (0.0);
int value64_4 = htole64 (0.0);
/* Make sure the variables get used. */
return !(value16_1 + value32_1 + value64_1
+ value16_2 + value32_2 + value64_2
+ value16_3 + value32_3 + value64_3
+ value16_4 + value32_4 + value64_4);
]])],
[gl_cv_header_working_endian_h=yes],
[gl_cv_header_working_endian_h=no])
])
else
HAVE_ENDIAN_H=0
fi
dnl Check if endian.h should be generated.
if test "$gl_cv_header_endian_h_stdint_types" = yes \
&& test "$gl_cv_header_working_endian_h" = yes; then
GL_GENERATE_ENDIAN_H=false
else
GL_GENERATE_ENDIAN_H=true
fi
dnl Check if endian.h works but is missing types from stdint.h.
if test $GL_GENERATE_ENDIAN_H; then
if test "$gl_cv_header_working_endian_h" = yes; then
ENDIAN_H_JUST_MISSING_STDINT=1
else
ENDIAN_H_JUST_MISSING_STDINT=0
fi
else
ENDIAN_H_JUST_MISSING_STDINT=0
fi
AC_SUBST([HAVE_ENDIAN_H])
AC_SUBST([ENDIAN_H_JUST_MISSING_STDINT])
])