1 files changed, 46 insertions, 28 deletions

diff --git a/gl/m4/memchr.m4 b/gl/m4/memchr.m4
index 2d8abe75..4f1aed01 100644
--- a/gl/m4/memchr.m4
+++ b/gl/m4/memchr.m4
@@ -1,35 +1,30 @@
-# memchr.m4 serial 12
-dnl Copyright (C) 2002-2004, 2009-2013 Free Software Foundation, Inc.
+# memchr.m4 serial 18
+dnl Copyright (C) 2002-2004, 2009-2023 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.
 
 AC_DEFUN_ONCE([gl_FUNC_MEMCHR],
 [
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+
   dnl Check for prerequisites for memory fence checks.
   gl_FUNC_MMAP_ANON
   AC_CHECK_HEADERS_ONCE([sys/mman.h])
   AC_CHECK_FUNCS_ONCE([mprotect])
 
-  AC_REQUIRE([gl_HEADER_STRING_H_DEFAULTS])
-  m4_ifdef([gl_FUNC_MEMCHR_OBSOLETE], [
-    dnl These days, we assume memchr is present.  But if support for old
-    dnl platforms is desired:
-    AC_CHECK_FUNCS_ONCE([memchr])
-    if test $ac_cv_func_memchr = no; then
-      HAVE_MEMCHR=0
-    fi
-  ])
-  if test $HAVE_MEMCHR = 1; then
-    # Detect platform-specific bugs in some versions of glibc:
-    # memchr should not dereference anything with length 0
-    #   http://bugzilla.redhat.com/499689
-    # memchr should not dereference overestimated length after a match
-    #   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737
-    #   http://sourceware.org/bugzilla/show_bug.cgi?id=10162
-    # Assume that memchr works on platforms that lack mprotect.
-    AC_CACHE_CHECK([whether memchr works], [gl_cv_func_memchr_works],
-      [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+  AC_REQUIRE([gl_STRING_H_DEFAULTS])
+  # Detect platform-specific bugs in some versions of glibc:
+  # memchr should not dereference anything with length 0
+  #   https://bugzilla.redhat.com/show_bug.cgi?id=499689
+  # memchr should not dereference overestimated length after a match
+  #   https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=521737
+  #   https://sourceware.org/bugzilla/show_bug.cgi?id=10162
+  # memchr should cast the second argument to 'unsigned char'.
+  #   This bug exists in Android 4.3.
+  # Assume that memchr works on platforms that lack mprotect.
+  AC_CACHE_CHECK([whether memchr works], [gl_cv_func_memchr_works],
+    [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
 #include <string.h>
 #if HAVE_SYS_MMAN_H
 # include <fcntl.h>
@@ -64,6 +59,7 @@ AC_DEFUN_ONCE([gl_FUNC_MEMCHR],
 #endif
   if (fence)
     {
+      /* Test against bugs on glibc systems.  */
       if (memchr (fence, 0, 0))
         result |= 1;
       strcpy (fence - 9, "12345678");
@@ -71,15 +67,37 @@ AC_DEFUN_ONCE([gl_FUNC_MEMCHR],
         result |= 2;
       if (memchr (fence - 1, 0, 3) != fence - 1)
         result |= 4;
+      /* Test against bug on AIX 7.2.  */
+      if (memchr (fence - 4, '6', 16) != fence - 4)
+        result |= 8;
     }
+  /* Test against bug on Android 4.3.  */
+  {
+    char input[3];
+    input[0] = 'a';
+    input[1] = 'b';
+    input[2] = 'c';
+    if (memchr (input, 0x789abc00 | 'b', 3) != input + 1)
+      result |= 16;
+  }
   return result;
-]])], [gl_cv_func_memchr_works=yes], [gl_cv_func_memchr_works=no],
-      [dnl Be pessimistic for now.
-       gl_cv_func_memchr_works="guessing no"])])
-    if test "$gl_cv_func_memchr_works" != yes; then
-      REPLACE_MEMCHR=1
-    fi
-  fi
+]])],
+       [gl_cv_func_memchr_works=yes],
+       [gl_cv_func_memchr_works=no],
+       [case "$host_os" in
+                           # Guess no on Android.
+          linux*-android*) gl_cv_func_memchr_works="guessing no" ;;
+                           # Guess yes on native Windows.
+          mingw*)          gl_cv_func_memchr_works="guessing yes" ;;
+                           # If we don't know, obey --enable-cross-guesses.
+          *)               gl_cv_func_memchr_works="$gl_cross_guess_normal" ;;
+        esac
+       ])
+    ])
+  case "$gl_cv_func_memchr_works" in
+    *yes) ;;
+    *) REPLACE_MEMCHR=1 ;;
+  esac
 ])
 
 # Prerequisites of lib/memchr.c.