It seems that libiberty already has replacements for most of the
mem* functions, but they are not published via include/libiberty.h.

Tested on x86_64 Linux, Darwin aarch64 Linux, OK for trunk?
thanks,
Iain

--- 8< ---

This adds an implementation of memrchr to libiberty and arranges
to configure gcc to use it, if the host does not have it.

gcc/ChangeLog:

        * config.in: Regenerate.
        * configure: Regenerate.
        * configure.ac: Check for host memrchr.

include/ChangeLog:

        * libiberty.h (memrchr): New.

libiberty/ChangeLog:

        * Makefile.in: Add memrchr build rules.
        * config.in: Regenerate.
        * configure: Regenerate.
        * configure.ac: Check for memrchr.
        * functions.texi: Document memrchr.
        * memrchr.c: New file.

Signed-off-by: Iain Sandoe <i...@sandoe.co.uk>
---
 gcc/config.in            |  6 ++++++
 gcc/configure            |  2 +-
 gcc/configure.ac         |  2 +-
 include/libiberty.h      | 10 ++++++++++
 libiberty/Makefile.in    | 17 +++++++++++++----
 libiberty/config.in      |  3 +++
 libiberty/configure      |  5 +++--
 libiberty/configure.ac   |  5 +++--
 libiberty/functions.texi | 14 ++++++++++++++
 libiberty/memrchr.c      | 33 +++++++++++++++++++++++++++++++++
 10 files changed, 87 insertions(+), 10 deletions(-)
 create mode 100644 libiberty/memrchr.c

diff --git a/gcc/config.in b/gcc/config.in
index 0d8a6ba1808..7c89cab7717 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -1960,6 +1960,12 @@
 #endif
 
 
+/* Define to 1 if you have the `memrchr' function. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_MEMRCHR
+#endif
+
+
 /* Define to 1 if you have the `mmap' function. */
 #ifndef USED_FOR_TARGET
 #undef HAVE_MMAP
diff --git a/gcc/configure b/gcc/configure
index 063b9ce6701..ab6bec1f0ae 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -10640,7 +10640,7 @@ for ac_func in times clock kill getrlimit setrlimit 
atoq \
        popen sysconf strsignal getrusage nl_langinfo \
        gettimeofday mbstowcs wcswidth mmap posix_fallocate setlocale \
        clearerr_unlocked feof_unlocked   ferror_unlocked fflush_unlocked 
fgetc_unlocked fgets_unlocked   fileno_unlocked fprintf_unlocked fputc_unlocked 
fputs_unlocked   fread_unlocked fwrite_unlocked getchar_unlocked getc_unlocked  
 putchar_unlocked putc_unlocked madvise mallinfo mallinfo2 fstatat getauxval \
-       clock_gettime munmap msync get_current_dir_name
+       clock_gettime munmap msync get_current_dir_name memrchr
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
 ac_fn_cxx_check_func "$LINENO" "$ac_func" "$as_ac_var"
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 3243472680c..fca0579574f 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -1574,7 +1574,7 @@ AC_CHECK_FUNCS(times clock kill getrlimit setrlimit atoq \
        popen sysconf strsignal getrusage nl_langinfo \
        gettimeofday mbstowcs wcswidth mmap posix_fallocate setlocale \
        gcc_UNLOCKED_FUNCS madvise mallinfo mallinfo2 fstatat getauxval \
-       clock_gettime munmap msync get_current_dir_name)
+       clock_gettime munmap msync get_current_dir_name memrchr)
 
 # At least for glibc, clock_gettime is in librt.  But don't pull that
 # in if it still doesn't give us the function we want.
diff --git a/include/libiberty.h b/include/libiberty.h
index f2e763a306a..d4e8791b14b 100644
--- a/include/libiberty.h
+++ b/include/libiberty.h
@@ -215,6 +215,16 @@ extern int ffs(int);
 extern int mkstemps(char *, int);
 #endif
 
+#if defined (HAVE_DECL_MKSTEMPS) && !HAVE_DECL_MKSTEMPS
+extern int mkstemps(char *, int);
+#endif
+
+/* Make memrchr available on systems that do not have it.  */
+#if !defined (__GNU_LIBRARY__ ) && !defined (__linux__) && \
+    !defined (HAVE_MEMRCHR)
+extern void *memrchr(const void *, int, size_t);
+#endif
+
 /* Get the working directory.  The result is cached, so don't call
    chdir() between calls to getpwd().  */
 
diff --git a/libiberty/Makefile.in b/libiberty/Makefile.in
index 4870fa95f2f..ce54d88278d 100644
--- a/libiberty/Makefile.in
+++ b/libiberty/Makefile.in
@@ -139,8 +139,8 @@ CFILES = alloca.c argv.c asprintf.c atexit.c                
                \
        ldirname.c                                                      \
        lrealpath.c                                                     \
        make-relative-prefix.c                                          \
-       make-temp-file.c md5.c memchr.c memcmp.c memcpy.c memmem.c      \
-        memmove.c mempcpy.c memset.c mkstemps.c                        \
+       make-temp-file.c md5.c memchr.c memrchr.c memcmp.c memcpy.c     \
+       memmem.c memmove.c mempcpy.c memset.c mkstemps.c                \
        objalloc.c obstack.c                                            \
        partition.c pexecute.c                                          \
         pex-common.c pex-djgpp.c pex-msdos.c pex-one.c                 \
@@ -213,8 +213,8 @@ CONFIGURED_OFILES = ./asprintf.$(objext) ./atexit.$(objext) 
        \
        ./getcwd.$(objext) ./getpagesize.$(objext)                      \
         ./gettimeofday.$(objext)                                       \
        ./index.$(objext) ./insque.$(objext)                            \
-       ./memchr.$(objext) ./memcmp.$(objext) ./memcpy.$(objext)        \
-       ./memmem.$(objext) ./memmove.$(objext)                          \
+       ./memchr.$(objext) ./memrchr.$(objext) ./memcmp.$(objext)       \
+       ./memcpy.$(objext) ./memmem.$(objext) ./memmove.$(objext)       \
         ./mempcpy.$(objext) ./memset.$(objext) ./mkstemps.$(objext)    \
        ./pex-djgpp.$(objext) ./pex-msdos.$(objext)                     \
         ./pex-unix.$(objext) ./pex-win32.$(objext)                     \
@@ -1025,6 +1025,15 @@ $(CONFIGURED_OFILES): stamp-picdir stamp-noasandir
        else true; fi
        $(COMPILE.c) $(srcdir)/memchr.c $(OUTPUT_OPTION)
 
+./memrchr.$(objext): $(srcdir)/memrchr.c $(INCDIR)/ansidecl.h
+       if [ x"$(PICFLAG)" != x ]; then \
+         $(COMPILE.c) $(PICFLAG) $(srcdir)/memrchr.c -o pic/$@; \
+       else true; fi
+       if [ x"$(NOASANFLAG)" != x ]; then \
+         $(COMPILE.c) $(PICFLAG) $(NOASANFLAG) $(srcdir)/memrchr.c -o 
noasan/$@; \
+       else true; fi
+       $(COMPILE.c) $(srcdir)/memrchr.c $(OUTPUT_OPTION)
+
 ./memcmp.$(objext): $(srcdir)/memcmp.c $(INCDIR)/ansidecl.h
        if [ x"$(PICFLAG)" != x ]; then \
          $(COMPILE.c) $(PICFLAG) $(srcdir)/memcmp.c -o pic/$@; \
diff --git a/libiberty/config.in b/libiberty/config.in
index b055150961c..3b8716511f0 100644
--- a/libiberty/config.in
+++ b/libiberty/config.in
@@ -186,6 +186,9 @@
 /* Define to 1 if you have the <memory.h> header file. */
 #undef HAVE_MEMORY_H
 
+/* Define to 1 if you have the `memrchr' function. */
+#undef HAVE_MEMRCHR
+
 /* Define to 1 if you have the `memset' function. */
 #undef HAVE_MEMSET
 
diff --git a/libiberty/configure b/libiberty/configure
index 347719c6262..02fbaabe89e 100755
--- a/libiberty/configure
+++ b/libiberty/configure
@@ -6210,6 +6210,7 @@ funcs="$funcs gettimeofday"
 funcs="$funcs index"
 funcs="$funcs insque"
 funcs="$funcs memchr"
+funcs="$funcs memrchr"
 funcs="$funcs memcmp"
 funcs="$funcs memcpy"
 funcs="$funcs memmem"
@@ -6276,7 +6277,7 @@ if test "x" = "y"; then
     ffs __fsetlocking \
     getcwd getpagesize getrlimit getrusage getsysinfo gettimeofday \
     index insque \
-    memchr memcmp memcpy memmem memmove memset mkstemps \
+    memchr memrchr memcmp memcpy memmem memmove memset mkstemps \
     on_exit \
     pipe2 posix_spawn posix_spawnp psignal \
     pstat_getdynamic pstat_getstatic putenv \
@@ -6691,7 +6692,7 @@ esac
 
     for f in atexit basename bcmp bcopy bsearch bzero calloc clock ffs \
              getcwd getpagesize getrusage gettimeofday \
-             index insque memchr memcmp memcpy memmove memset psignal \
+             index insque memchr memrchr memcmp memcpy memmove memset psignal \
              putenv random rename rindex sbrk setenv stpcpy strcasecmp \
              strchr strdup strerror strncasecmp strrchr strstr strtod \
              strtol strtoul sysconf times tmpnam vfprintf vprintf \
diff --git a/libiberty/configure.ac b/libiberty/configure.ac
index 5bad0f93692..3de5eca0df2 100644
--- a/libiberty/configure.ac
+++ b/libiberty/configure.ac
@@ -370,6 +370,7 @@ funcs="$funcs gettimeofday"
 funcs="$funcs index"
 funcs="$funcs insque"
 funcs="$funcs memchr"
+funcs="$funcs memrchr"
 funcs="$funcs memcmp"
 funcs="$funcs memcpy"
 funcs="$funcs memmem"
@@ -436,7 +437,7 @@ if test "x" = "y"; then
     ffs __fsetlocking \
     getcwd getpagesize getrlimit getrusage getsysinfo gettimeofday \
     index insque \
-    memchr memcmp memcpy memmem memmove memset mkstemps \
+    memchr memrchr memcmp memcpy memmem memmove memset mkstemps \
     on_exit \
     pipe2 posix_spawn posix_spawnp psignal \
     pstat_getdynamic pstat_getstatic putenv \
@@ -555,7 +556,7 @@ if test -n "${with_target_subdir}"; then
 
     for f in atexit basename bcmp bcopy bsearch bzero calloc clock ffs \
              getcwd getpagesize getrusage gettimeofday \
-             index insque memchr memcmp memcpy memmove memset psignal \
+             index insque memchr memrchr memcmp memcpy memmove memset psignal \
              putenv random rename rindex sbrk setenv stpcpy strcasecmp \
              strchr strdup strerror strncasecmp strrchr strstr strtod \
              strtol strtoul sysconf times tmpnam vfprintf vprintf \
diff --git a/libiberty/functions.texi b/libiberty/functions.texi
index b56b02e0686..7c7da1ba296 100644
--- a/libiberty/functions.texi
+++ b/libiberty/functions.texi
@@ -749,6 +749,20 @@ returned.
 
 @end deftypefn
 
+@c memrchr.c:3
+@deftypefn Supplemental void* memrchr (const void *@var{s}, int @var{c}, @
+  size_t @var{n})
+
+This function searches memory for the character @var{c} in reverse order,
+starting at @code{*@var{s}+@var{n}-1} .  The search only ends with
+the first occurrence of @var{c}, or when the start us reached; in particular,
+a null character does not terminate the search.  If the character @var{c} is
+found within @var{length} characters of @code{*@var{s}}, a pointer
+to the character is returned.  If @var{c} is not found, then @code{NULL} is
+returned.
+
+@end deftypefn
+
 @c memcmp.c:6
 @deftypefn Supplemental int memcmp (const void *@var{x}, const void *@var{y}, @
   size_t @var{count})
diff --git a/libiberty/memrchr.c b/libiberty/memrchr.c
new file mode 100644
index 00000000000..fe7713ecce5
--- /dev/null
+++ b/libiberty/memrchr.c
@@ -0,0 +1,33 @@
+/*
+
+@deftypefn Supplemental void* memrchr (const void *@var{s}, int @var{c}, @
+  size_t @var{n})
+
+This function searches memory for the character @var{c} in reverse order,
+starting at @code{*@var{s}+@var{n}-1} .  The search only ends with
+the first occurrence of @var{c}, or when the start us reached; in particular,
+a null character does not terminate the search.  If the character @var{c} is
+found within @var{length} characters of @code{*@var{s}}, a pointer
+to the character is returned.  If @var{c} is not found, then @code{NULL} is
+returned.
+
+@end deftypefn
+
+*/
+
+#include <ansidecl.h>
+#include <stddef.h>
+
+void *
+memrchr (const void *src_void, int c, size_t length)
+{
+  if (length == 0)
+    return NULL;
+
+  const unsigned char *p = (const unsigned char*)src_void;
+  p += length;
+  while (*--p != (unsigned char)c)
+    if (src_void == p)
+      return NULL;
+  return (void *)p;
+}
-- 
2.39.2 (Apple Git-143)

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