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Diffstat (limited to 'gl/m4/memmem.m4')
| -rw-r--r-- | gl/m4/memmem.m4 | 155 |
1 files changed, 155 insertions, 0 deletions
diff --git a/gl/m4/memmem.m4 b/gl/m4/memmem.m4 new file mode 100644 index 0000000..e01aa5c --- /dev/null +++ b/gl/m4/memmem.m4 @@ -0,0 +1,155 @@ +# memmem.m4 serial 29 +dnl Copyright (C) 2002-2004, 2007-2022 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 Check that memmem is present and functional. +AC_DEFUN([gl_FUNC_MEMMEM_SIMPLE], +[ + dnl Persuade glibc <string.h> to declare memmem(). + AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS]) + + AC_REQUIRE([gl_STRING_H_DEFAULTS]) + AC_CHECK_FUNCS([memmem]) + if test $ac_cv_func_memmem = yes; then + HAVE_MEMMEM=1 + else + HAVE_MEMMEM=0 + fi + AC_CHECK_DECLS_ONCE([memmem]) + if test $ac_cv_have_decl_memmem = no; then + HAVE_DECL_MEMMEM=0 + else + dnl Detect https://sourceware.org/bugzilla/show_bug.cgi?id=12092. + dnl Also check that we handle empty needles correctly. + AC_CACHE_CHECK([whether memmem works], + [gl_cv_func_memmem_works_always], + [AC_RUN_IFELSE([AC_LANG_PROGRAM([[ +#include <string.h> /* for memmem */ +#define P "_EF_BF_BD" +#define HAYSTACK "F_BD_CE_BD" P P P P "_C3_88_20" P P P "_C3_A7_20" P +#define NEEDLE P P P P P +]], [[ + int result = 0; + if (memmem (HAYSTACK, strlen (HAYSTACK), NEEDLE, strlen (NEEDLE))) + result |= 1; + /* Check for empty needle behavior. */ + { + const char *haystack = "AAA"; + if (memmem (haystack, 3, (const char *) 1, 0) != haystack) + result |= 2; + } + return result; + ]])], + [gl_cv_func_memmem_works_always=yes], + [gl_cv_func_memmem_works_always=no], + [dnl glibc 2.9..2.12 and cygwin 1.7.7 have issue #12092 above. + dnl Also empty needles work on glibc >= 2.1 and cygwin >= 1.7.0. + dnl uClibc is not affected, since it uses different source code. + dnl Assume that it works on all other platforms (even if not linear). + AC_EGREP_CPP([Lucky user], + [ +#include <string.h> /* for __GNU_LIBRARY__ */ +#ifdef __GNU_LIBRARY__ + #include <features.h> + #if ((__GLIBC__ == 2 && ((__GLIBC_MINOR > 0 && __GLIBC_MINOR__ < 9) \ + || __GLIBC_MINOR__ > 12)) \ + || (__GLIBC__ > 2)) \ + || defined __UCLIBC__ + Lucky user + #endif +#elif defined __CYGWIN__ + #include <cygwin/version.h> + #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 7) + Lucky user + #endif +#else + Lucky user +#endif + ], + [gl_cv_func_memmem_works_always="guessing yes"], + [gl_cv_func_memmem_works_always="$gl_cross_guess_normal"]) + ]) + ]) + case "$gl_cv_func_memmem_works_always" in + *yes) ;; + *) + REPLACE_MEMMEM=1 + ;; + esac + fi + gl_PREREQ_MEMMEM +]) # gl_FUNC_MEMMEM_SIMPLE + +dnl Additionally, check that memmem has linear performance characteristics +AC_DEFUN([gl_FUNC_MEMMEM], +[ + AC_REQUIRE([gl_FUNC_MEMMEM_SIMPLE]) + if test $HAVE_DECL_MEMMEM = 1 && test $REPLACE_MEMMEM = 0; then + AC_CACHE_CHECK([whether memmem works in linear time], + [gl_cv_func_memmem_works_fast], + [AC_RUN_IFELSE([AC_LANG_PROGRAM([[ +#include <signal.h> /* for signal */ +#include <string.h> /* for memmem */ +#include <stdlib.h> /* for malloc */ +#include <unistd.h> /* for alarm */ +static void quit (int sig) { _exit (sig + 128); } +]], [[ + int result = 0; + size_t m = 1000000; + char *haystack = (char *) malloc (2 * m + 1); + char *needle = (char *) malloc (m + 1); + /* Failure to compile this test due to missing alarm is okay, + since all such platforms (mingw) also lack memmem. */ + signal (SIGALRM, quit); + alarm (5); + /* Check for quadratic performance. */ + if (haystack && needle) + { + memset (haystack, 'A', 2 * m); + haystack[2 * m] = 'B'; + memset (needle, 'A', m); + needle[m] = 'B'; + if (!memmem (haystack, 2 * m + 1, needle, m + 1)) + result |= 1; + } + /* Free allocated memory, in case some sanitizer is watching. */ + free (haystack); + free (needle); + return result; + ]])], + [gl_cv_func_memmem_works_fast=yes], [gl_cv_func_memmem_works_fast=no], + [dnl Only glibc >= 2.9 and cygwin > 1.7.0 are known to have a + dnl memmem that works in linear time. + AC_EGREP_CPP([Lucky user], + [ +#include <features.h> +#ifdef __GNU_LIBRARY__ + #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 9) || (__GLIBC__ > 2)) \ + && !defined __UCLIBC__ + Lucky user + #endif +#endif +#ifdef __CYGWIN__ + #include <cygwin/version.h> + #if CYGWIN_VERSION_DLL_COMBINED > CYGWIN_VERSION_DLL_MAKE_COMBINED (1007, 0) + Lucky user + #endif +#endif + ], + [gl_cv_func_memmem_works_fast="guessing yes"], + [gl_cv_func_memmem_works_fast="$gl_cross_guess_normal"]) + ]) + ]) + case "$gl_cv_func_memmem_works_fast" in + *yes) ;; + *) + REPLACE_MEMMEM=1 + ;; + esac + fi +]) # gl_FUNC_MEMMEM + +# Prerequisites of lib/memmem.c. +AC_DEFUN([gl_PREREQ_MEMMEM], [:]) |