[PR build/24886] disable glibc mcheck support

This patch drops gdb's configury support for glibc's mcheck function.
It has been observed to cause false abort()s, because it is
thread-unsafe yet interposes every malloc/free operation.  So if any
library transitively used by gdb also uses threads, then these
functions can easily corrupt their own checking data.  These days, gcc
ASAN and valgrind provide high quality checking, and mcheck is
apparently itself being slowly deprecated.

So, let's stop linking to it.  Attached patch drops the
autoconf/Makefile machinery for both gdb and gdbserver.  No
testsuite-visible impact.  IMHO not worth mentioning in NEWS.

See also: https://sourceware.org/bugzilla/show_bug.cgi?id=9939

gdb/ChangeLog

        PR build/24886
        * configure.ac: Drop enable-libmcheck support.
        * configure, config.in: Rebuild.
        * libmcheck.m4: Remove.
        * acinclude.m4: Don't include it.
        * Makefile.in: Don't distribute it.
        * top.c (print_gdb_configuration): Don't mention it.

gdb/gdbserver/ChangeLog

        PR build/24886
        * configure.ac: Drop enable-libmcheck support.
        * configure, config.in: Rebuild.
        * acinclude.m4: Don't include it.

1 files changed, 0 insertions, 81 deletions

diff --git a/gdb/configure b/gdb/configure
index 12954d1..9206f0e 100755
--- a/gdb/configure
+++ b/gdb/configure
@@ -879,7 +879,6 @@ with_libmpfr_prefix
 with_python
 with_guile
 enable_source_highlight
-enable_libmcheck
 with_intel_pt
 with_libipt_prefix
 with_included_regex
@@ -1556,7 +1555,6 @@ Optional Features:
   --disable-rpath         do not hardcode runtime library paths
   --enable-source-highlight
                           enable source-highlight for source listings
-  --enable-libmcheck      Try linking with -lmcheck if available
   --enable-werror         treat compile warnings as errors
   --enable-build-warnings enable build-time compiler warnings if gcc is used
   --enable-gdb-build-warnings
@@ -11316,85 +11314,6 @@ fi
 
 
 
-# --------------------- #
-# Check for libmcheck.  #
-# --------------------- #
-
-# Enable -lmcheck by default (it provides cheap-enough memory mangling),
-# but turn it off if Python is enabled with threads, since -lmcheck is
-# not thread safe (http://sourceware.org/bugzilla/show_bug.cgi?id=9939),
-# and for releases.
-if test \( "${have_libpython}" = "no" -o "${python_has_threads}" = "no" \) \
-   && $development; then
-  libmcheck_default=yes
-else
-  libmcheck_default=no
-fi
-
-  # Check whether --enable-libmcheck was given.
-if test "${enable_libmcheck+set}" = set; then :
-  enableval=$enable_libmcheck; case "${enableval}" in
-      yes | y) ENABLE_LIBMCHECK="yes" ;;
-      no | n)  ENABLE_LIBMCHECK="no" ;;
-      *) as_fn_error $? "bad value ${enableval} for --enable-libmcheck" "$LINENO" 5 ;;
-    esac
-fi
-
-
-  if test -z "${ENABLE_LIBMCHECK}"; then
-    ENABLE_LIBMCHECK=${libmcheck_default}
-  fi
-
-  if test "$ENABLE_LIBMCHECK" = "yes" ; then
-    { $as_echo "$as_me:${as_lineno-$LINENO}: checking for main in -lmcheck" >&5
-$as_echo_n "checking for main in -lmcheck... " >&6; }
-if ${ac_cv_lib_mcheck_main+:} false; then :
-  $as_echo_n "(cached) " >&6
-else
-  ac_check_lib_save_LIBS=$LIBS
-LIBS="-lmcheck  $LIBS"
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h.  */
-
-
-int
-main ()
-{
-return main ();
-  ;
-  return 0;
-}
-_ACEOF
-if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_lib_mcheck_main=yes
-else
-  ac_cv_lib_mcheck_main=no
-fi
-rm -f core conftest.err conftest.$ac_objext \
-    conftest$ac_exeext conftest.$ac_ext
-LIBS=$ac_check_lib_save_LIBS
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_mcheck_main" >&5
-$as_echo "$ac_cv_lib_mcheck_main" >&6; }
-if test "x$ac_cv_lib_mcheck_main" = xyes; then :
-  cat >>confdefs.h <<_ACEOF
-#define HAVE_LIBMCHECK 1
-_ACEOF
-
-  LIBS="-lmcheck $LIBS"
-
-fi
-
-  fi
-
-
-if test "$ENABLE_LIBMCHECK" = "yes" \
-	-a "${have_libpython}" != "no" \
-	-a "${python_has_threads}" = "yes" ; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: --enable-libmcheck may lead to spurious crashes if threads are used in python" >&5
-$as_echo "$as_me: WARNING: --enable-libmcheck may lead to spurious crashes if threads are used in python" >&2;}
-fi
-
 
 # Check whether --with-intel_pt was given.
 if test "${with_intel_pt+set}" = set; then :