https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63645
Bug ID: 63645
Summary: Incorrect code generation
Product: gcc
Version: 4.8.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: terra at gnome dot org
Created attachment 33809
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33809&action=edit
Test program
I am observing valgrind errors from the to-be-attached reduced
test case. The oper test on line 36 should fail and short circuit
the rest of the condition, but that is not what seems to happen.
Note: this smells like an aliasing issue, but I think what union
access is correct.
welinder@lenovo ~ $ gcc -Wall -g -O2 vvv.c
welinder@lenovo ~ $ valgrind ./a.out
==4994== Memcheck, a memory error detector
==4994== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==4994== Using Valgrind-3.10.0.SVN and LibVEX; rerun with -h for copyright info
==4994== Command: ./a.out
==4994==
==4994== Invalid read of size 8
==4994== at 0x4005E8: test (vvv.c:36)
==4994== by 0x4004D8: main (vvv.c:47)
==4994== Address 0x51fd040 is 0 bytes inside a block of size 1 alloc'd
==4994== at 0x4C2AB80: malloc (in
/usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4994== by 0x4005DA: test (vvv.c:54)
==4994== by 0x4004D8: main (vvv.c:47)
welinder@lenovo ~ $ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.8/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.8.2-19ubuntu1'
--with-bugurl=file:///usr/share/doc/gcc-4.8/README.Bugs
--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.8 --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.8 --libdir=/usr/lib --enable-nls
--with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-libmudflap
--enable-plugin --with-system-zlib --disable-browser-plugin
--enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64/jre --enable-java-home
--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.8-amd64
--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.8-amd64
--with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar
--enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686
--with-abi=m64 --with-multilib-list=m32,m64,mx32 --with-tune=generic
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1)
