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configure: disable FORTIFY_SOURCE under clang

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Some versions of clang may have difficulty compiling glibc headers when
-D_FORTIFY_SOURCE is used. For example, Clang++ 3.5.0-9.fc22 cannot
compile glibc's stdio headers when -D_FORTIFY_SOURCE=2 is used. This
manifests currently as build failures with clang and any arm target.

According to LLVM dev Richard Smith, clang does not target or support
FORTIFY_SOURCE + glibc, and it should not be relied on.
"It's still an unsupported combination, and while it might compile, some
of the checks are unlikely to work because they require a frontend
inliner to be useful"

See: http://lists.llvm.org/pipermail/cfe-dev/2015-November/045846.html

Conclusion: disable fortify-source if we appear to be using clang instead
of testing for compile success or failure, which may be incidental or not
indicative of proper support of the feature.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <1446583422-10153-1-git-send-email-jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
John Snow 2015-11-03 15:43:42 -05:00 committed by Paolo Bonzini
parent 8d31d6b65a
commit b553a04280
1 changed files with 16 additions and 1 deletions
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17
configure vendored
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@ -264,6 +264,7 @@ rdma=""
gprof="no"
debug_tcg="no"
debug="no"
fortify_source=""
strip_opt="yes"
tcg_interpreter="no"
bigendian="no"
@ -879,6 +880,7 @@ for opt do
debug_tcg="yes"
debug="yes"
strip_opt="no"
fortify_source="no"
;;
--enable-sparse) sparse="yes"
;;
@ -4439,6 +4441,19 @@ if ! compile_object "-Werror"; then
ccache_cpp2=yes
fi
#################################################
# clang does not support glibc + FORTIFY_SOURCE.
if test "$fortify_source" != "no"; then
if echo | $cc -dM -E - | grep __clang__ > /dev/null 2>&1 ; then
fortify_source="no";
elif echo | $cxx -dM -E - | grep __clang__ > /dev/null 2>&1 ; then
fortify_source="no";
else
fortify_source="yes"
fi
fi
##########################################
# End of CC checks
# After here, no more $cc or $ld runs
@ -4446,7 +4461,7 @@ fi
if test "$gcov" = "yes" ; then
CFLAGS="-fprofile-arcs -ftest-coverage -g $CFLAGS"
LDFLAGS="-fprofile-arcs -ftest-coverage $LDFLAGS"
elif test "$debug" = "no" ; then
elif test "$fortify_source" = "yes" ; then
CFLAGS="-O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 $CFLAGS"
fi