From 5ee811110444a615bbbf84a3daacccf734e4ef2c Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Wed, 16 Jul 2014 21:32:06 -0400 Subject: work around constant folding bug 61144 in gcc 4.9.0 and 4.9.1 previously we detected this bug in configure and issued advice for a workaround, but this turned out not to work. since then gcc 4.9.0 has appeared in several distributions, and now 4.9.1 has been released without a fix despite this being a wrong code generation bug which is supposed to be a release-blocker, per gcc policy. since the scope of the bug seems to affect only data objects (rather than functions) whose definitions are overridable, and there are only a very small number of these in musl, I am just changing them from const to volatile for the time being. simply removing the const would be sufficient to make gcc 4.9.1 work (the non-const case was inadvertently fixed as part of another change in gcc), and this would also be sufficient with 4.9.0 if we forced -O0 on the affected files or on the whole build. however it's cleaner to just remove all the broken compiler detection and use volatile, which will ensure that they are never constant-folded. the quality of a non-broken compiler's output should not be affected except for the fact that these objects are no longer const and thus possibly add a few bytes to data/bss. this change can be reconsidered and possibly reverted at some point in the future when the broken gcc versions are no longer relevant. (cherry picked from commit a6adb2bcd8145353943377d6119c1d7a4242bae1) --- configure | 21 --------------------- 1 file changed, 21 deletions(-) (limited to 'configure') diff --git a/configure b/configure index 03c193d9..fa5613e6 100755 --- a/configure +++ b/configure @@ -495,27 +495,6 @@ printf "no\n" fail "$0: error: unsupported long double type" fi -# -# Check for known bug in GCC 4.9.0 that results in a broken libc. -# -if test "$cc_is_gcc" = yes ; then -printf "checking for gcc constant folding bug with weak aliases... " -echo 'static int x = 0;' > "$tmpc" -echo 'extern int y __attribute__((__weak__, __alias__("x")));' >> "$tmpc" -echo 'extern int should_appear;' >> "$tmpc" -echo 'int foo() { return y ? should_appear : 0; }' >> "$tmpc" -case "$($CC $CFLAGS_C99FSE -I./arch/$ARCH -I./include \ - $CPPFLAGS $CFLAGS_AUTO $CFLAGS -S -o - "$tmpc" 2>/dev/null)" in -*should_appear*) -printf "no\n" -;; -*) -printf "yes\n" -fail "$0: error: broken compiler; try CFLAGS=-fno-toplevel-reorder" -;; -esac -fi - printf "creating config.mak... " cmdline=$(quote "$0") -- cgit v1.2.1