From a6adb2bcd8145353943377d6119c1d7a4242bae1 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. --- src/stdio/__stdio_exit.c | 2 +- src/stdio/fflush.c | 2 +- src/stdio/stderr.c | 2 +- src/stdio/stdin.c | 2 +- src/stdio/stdout.c | 2 +- 5 files changed, 5 insertions(+), 5 deletions(-) (limited to 'src/stdio') diff --git a/src/stdio/__stdio_exit.c b/src/stdio/__stdio_exit.c index e4380aaf..716e5f73 100644 --- a/src/stdio/__stdio_exit.c +++ b/src/stdio/__stdio_exit.c @@ -1,6 +1,6 @@ #include "stdio_impl.h" -static FILE *const dummy_file = 0; +static FILE *volatile dummy_file = 0; weak_alias(dummy_file, __stdin_used); weak_alias(dummy_file, __stdout_used); weak_alias(dummy_file, __stderr_used); diff --git a/src/stdio/fflush.c b/src/stdio/fflush.c index af709503..7bf862a6 100644 --- a/src/stdio/fflush.c +++ b/src/stdio/fflush.c @@ -19,7 +19,7 @@ static int __fflush_unlocked(FILE *f) } /* stdout.c will override this if linked */ -static FILE *const dummy = 0; +static FILE *volatile dummy = 0; weak_alias(dummy, __stdout_used); int fflush(FILE *f) diff --git a/src/stdio/stderr.c b/src/stdio/stderr.c index 3fd8f81d..229c8651 100644 --- a/src/stdio/stderr.c +++ b/src/stdio/stderr.c @@ -13,4 +13,4 @@ static FILE f = { .lock = -1, }; FILE *const stderr = &f; -FILE *const __stderr_used = &f; +FILE *volatile __stderr_used = &f; diff --git a/src/stdio/stdin.c b/src/stdio/stdin.c index 476dc708..171ff22a 100644 --- a/src/stdio/stdin.c +++ b/src/stdio/stdin.c @@ -12,4 +12,4 @@ static FILE f = { .lock = -1, }; FILE *const stdin = &f; -FILE *const __stdin_used = &f; +FILE *volatile __stdin_used = &f; diff --git a/src/stdio/stdout.c b/src/stdio/stdout.c index 3855dd0b..6b188942 100644 --- a/src/stdio/stdout.c +++ b/src/stdio/stdout.c @@ -13,4 +13,4 @@ static FILE f = { .lock = -1, }; FILE *const stdout = &f; -FILE *const __stdout_used = &f; +FILE *volatile __stdout_used = &f; -- cgit v1.2.1