Fix AIX libstdc++ semaphore support [PR100164]

> > The #error would not be hit if _GLIBCXX_HAVE_POSIX_SEMAPHORE were defined,
> > but it shows up in your error report.

> You now have pinpointed the problem.

> It's not that AIX doesn't have semaphore, but that the code previously
> had a fallback that hid a bug in the macros:

  // Use futex if available and didn't force use of POSIX
  using __fast_semaphore = __atomic_semaphore<__detail::__platform_wait_t>;
  using __fast_semaphore = __platform_semaphore;
  using __fast_semaphore = __atomic_semaphore<ptrdiff_t>;

> The problem is that libstdc++ configure defines
> _GLIBCXX_HAVE_POSIX_SEMAPHORE in config.h.  libstdc++ uses sed to
> rewrite config.h to c++config.h and prepends _GLIBCXX_, so c++config.h
> contains

> And bits/semaphore_base.h is not testing that corrupted macro.  Either
> semaphore_base.h needs to test for the corrupted macro, or libtsdc++
> configure needs to define HAVE_POSIX_SEMAPHORE without itself
> prepending _GLIBCXX_  so that the c++config.h rewriting works
> correctly and defines the correct macro for semaphore_base.h.

The include/Makefile.am sed is:
        sed -e 's/HAVE_/_GLIBCXX_HAVE_/g' \
            -e 's/PACKAGE/_GLIBCXX_PACKAGE/g' \
            -e 's/VERSION/_GLIBCXX_VERSION/g' \
            -e 's/WORDS_/_GLIBCXX_WORDS_/g' \
            -e 's/_DARWIN_USE_64_BIT_INODE/_GLIBCXX_DARWIN_USE_64_BIT_INODE/g' \
            -e 's/_FILE_OFFSET_BITS/_GLIBCXX_FILE_OFFSET_BITS/g' \
            -e 's/_LARGE_FILES/_GLIBCXX_LARGE_FILES/g' \
            -e 's/ICONV_CONST/_GLIBCXX_ICONV_CONST/g' \
            -e '/[       ]_GLIBCXX_LONG_DOUBLE_COMPAT[   ]/d' \
            -e '/[       ]_GLIBCXX_LONG_DOUBLE_ALT128_COMPAT[    ]/d' \
            < ${CONFIG_HEADER} >> $@ ;\
so for many macros one needs _GLIBCXX_ prefixes already in configure,
as can be seen in grep AC_DEFINE.*_GLIBCXX configure.ac acinclude.m4
But _GLIBCXX_HAVE_POSIX_SEMAPHORE is the only one that shouldn't have
that prefix because the sed is adding that.
E.g. on i686-linux, I see
grep _GLIBCXX__GLIBCXX c++config.h
that proves it is the only broken one.

So this change fixes the acinclude.m4 side.

2021-04-21  Jakub Jelinek  <jakub@redhat.com>

	PR libstdc++/100164
	* acinclude.m4: For POSIX semaphores AC_DEFINE HAVE_POSIX_SEMAPHORE
	rather than _GLIBCXX_HAVE_POSIX_SEMAPHORE.
	* configure: Regenerated.
	* config.h.in: Regenerated.

diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index e4175ea..1c0a4c1 100644 (file)
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4097,7 +4097,7 @@ AC_DEFUN([GLIBCXX_CHECK_GTHREADS], [
       [ac_have_posix_semaphore=no])
 
   if test $ac_have_posix_semaphore = yes ; then
-    AC_DEFINE(_GLIBCXX_HAVE_POSIX_SEMAPHORE,
+    AC_DEFINE(HAVE_POSIX_SEMAPHORE,
              1,
              [Define to 1 if POSIX Semaphores with sem_timedwait are available in <semaphore.h>.])
   fi

diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in
index d36ca26..37b56b8 100644 (file)
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -291,6 +291,10 @@
 /* Define to 1 if you have the `posix_memalign' function. */
 #undef HAVE_POSIX_MEMALIGN
 
+/* Define to 1 if POSIX Semaphores with sem_timedwait are available in
+   <semaphore.h>. */
+#undef HAVE_POSIX_SEMAPHORE
+
 /* Define to 1 if you have the `powf' function. */
 #undef HAVE_POWF
 
@@ -818,10 +822,6 @@
 /* Define if gthreads library is available. */
 #undef _GLIBCXX_HAS_GTHREADS
 
-/* Define to 1 if POSIX Semaphores with sem_timedwait are available in
-   <semaphore.h>. */
-#undef _GLIBCXX_HAVE_POSIX_SEMAPHORE
-
 /* Define to 1 if a full hosted library is built, or 0 if freestanding. */
 #undef _GLIBCXX_HOSTED
 

diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 13f2e69..326a279 100755 (executable)
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -75836,7 +75836,7 @@ fi
 
   if test $ac_have_posix_semaphore = yes ; then
 
-$as_echo "#define _GLIBCXX_HAVE_POSIX_SEMAPHORE 1" >>confdefs.h
+$as_echo "#define HAVE_POSIX_SEMAPHORE 1" >>confdefs.h
 
   fi
   { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_have_posix_semaphore" >&5