http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52326
Bug #: 52326
Summary: float result incorrect with -O1 and calling external
function.
Classification: Unclassified
Product: gcc
Version: 4.6.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: bauge...@cisco.com
Created attachment 26713
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26713
Two source files, one header file and a Makefile
The sample program attached fails when built with -O1, but not with any other
optimization levels (0,2,3). Unfortunately it only fails when we call an
external function, therefore we had to attach a tgz file instead of a
preprocessed file.
The tar file contains four files: main.c, foo.c, foo.h and a Makefile. The
Makefile, which builds two targets (fail and success) can be used to re-create
the problem as well as to build a non-failing version.
Also, the error only occurs when certain other conditions are met. We've
written a C comment for every condition we found in the source file named
main.c. Please search for the text "NOTE".
GCC Version:
------------
Our GCC version is 4.6.2. It fails on multiple versions/builds of 4.6.2, both
the one provided with Gentoo and the one provided by Centos 6. The info below
is from my Gentoo host:
COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.6.2/gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.6.2/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-4.6.2/work/gcc-4.6.2/configure
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.6.2
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.2/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.2
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.2/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.2/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.2/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec
--disable-fixed-point --without-ppl --without-cloog --enable-lto --enable-nls
--without-included-gettext --with-system-zlib --disable-werror
--enable-secureplt --enable-multilib --enable-libmudflap --disable-libssp
--enable-libgomp
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.6.2/python
--enable-checking=release --disable-libgcj --disable-libquadmath
--enable-languages=c,c++ --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu --enable-targets=all
--with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo 4.6.2 p1.4,
pie-0.5.0'
Thread model: posix
gcc version 4.6.2 (Gentoo 4.6.2 p1.4, pie-0.5.0)
The complete command line that triggers the bug:
------------------------------------------------
gcc -o fail -O1 -Wall -Wextra -Wconversion -Werror -Wshadow
-Wmissing-declarations -std=c89 main.c foo.c && ./fail
(Note that it also fails with less arguments, -O1 is all it takes)
Compiler output:
---------------
None
Preprocessed file:
------------------
Due to the nature of the bug, calling an external function, we could not
provide a preprocessed file.
