http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51862
Bug #: 51862
Summary: Over optimization for assignments to char[] defined
inner than used
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: nar...@airemix.jp
GCC 4.7 optimization out assignments to char[] if the char[] is defined inner
than it is used.
The too simplified case is like following (func() changes buf and enough small
to inline):
char *res;
if (bool) {
char buf[4];
func(buf);
res = buf;
}
fprintf(stderr, "'%s'\n", res);
= gcc47 -v
Using built-in specs.
COLLECT_GCC=gcc47
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/lto-wrapper
Target: x86_64-portbld-freebsd9.0
Configured with: ./../gcc-4.7-20111217/configure --disable-nls
--enable-languages=c,c++,fortran --libdir=/usr/local/lib/gcc47
--libexecdir=/usr/local/libexec/gcc47 --program-suffix=47
--with-as=/usr/local/bin/as --with-gmp=/usr/local
--with-gxx-include-dir=/usr/local/lib/gcc47/include/c++/
--with-ld=/usr/local/bin/ld --with-libiconv-prefix=/usr/local
--with-pkgversion='FreeBSD Ports Collection' --with-system-zlib
--disable-libgcj --prefix=/usr/local --mandir=/usr/local/man
--infodir=/usr/local/info/gcc47 --build=x86_64-portbld-freebsd9.0
Thread model: posix
gcc version 4.7.0 20111217 (experimental) (FreeBSD Ports Collection)
= the complete command line that triggers the bug
% gcc47 -O2 g.c&&./a.out # type "\u0061"
\u0061
1 ''
The resulted output must be following and works with -O0:
1 'a????'
= the compiler output (error messages, warnings, etc.)
Using built-in specs.
COLLECT_GCC=gcc47
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/lto-wrapper
Target: x86_64-portbld-freebsd9.0
Configured with: ./../gcc-4.7-20111217/configure --disable-nls
--enable-languages=c,c++,fortran --li
bdir=/usr/local/lib/gcc47 --libexecdir=/usr/local/libexec/gcc47
--program-suffix=47 --with-as=/usr/l
ocal/bin/as --with-gmp=/usr/local
--with-gxx-include-dir=/usr/local/lib/gcc47/include/c++/ --with-ld
=/usr/local/bin/ld --with-libiconv-prefix=/usr/local --with-pkgversion='FreeBSD
Ports Collection' --
with-system-zlib --disable-libgcj --prefix=/usr/local --mandir=/usr/local/man
--infodir=/usr/local/i
nfo/gcc47 --build=x86_64-portbld-freebsd9.0
Thread model: posix
gcc version 4.7.0 20111217 (experimental) (FreeBSD Ports Collection)
COLLECT_GCC_OPTIONS='-O2' '-save-temps' '-v' '-mtune=generic' '-march=x86-64'
/usr/local/libexec/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/cc1 -E -quiet -v
g.c -mtune=generic -m
arch=x86-64 -O2 -fpch-preprocess -o g.i
ignoring nonexistent directory
"/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/../../../..
/../x86_64-portbld-freebsd9.0/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/include
/usr/local/include
/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/include-fixed
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-O2' '-save-temps' '-v' '-mtune=generic' '-march=x86-64'
/usr/local/libexec/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/cc1
-fpreprocessed g.i -quiet -dumpbase g.c -mtune=generic -march=x86-64 -auxbase g
-O2 -version -o g.s
GNU C (FreeBSD Ports Collection) version 4.7.0 20111217 (experimental)
(x86_64-portbld-freebsd9.0)
compiled by GNU C version 4.7.0 20111217 (experimental), GMP version
5.0.2, MPFR version 3.1.0-p3, MPC version 0.9
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
GNU C (FreeBSD Ports Collection) version 4.7.0 20111217 (experimental)
(x86_64-portbld-freebsd9.0)
compiled by GNU C version 4.7.0 20111217 (experimental), GMP version
5.0.2, MPFR version 3.1.0-p3, MPC version 0.9
GGC heuristics: --param ggc-min-expand=30 --param ggc-min-heapsize=4096
Compiler executable checksum: 7130d1c9d6c474bcedaf92254d46803f
COLLECT_GCC_OPTIONS='-O2' '-save-temps' '-v' '-mtune=generic' '-march=x86-64'
/usr/local/bin/as -v -o g.o g.s
GNU assembler version 2.22 (x86_64-portbld-freebsd9.0) using BFD version (GNU
Binutils) 2.22
COMPILER_PATH=/usr/local/libexec/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/:/usr/local/libexec/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/:/usr/local/libexec/gcc47/gcc/x86_64-portbld-freebsd9.0/:/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/:/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/:/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/../../../../../x86_64-portbld-freebsd9.0/bin/
LIBRARY_PATH=/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/:/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/../../../../../x86_64-portbld-freebsd9.0/lib/:/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-O2' '-save-temps' '-v' '-mtune=generic' '-march=x86-64'
/usr/local/libexec/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/collect2
--eh-frame-hdr -V -dynamic-linker /libexec/ld-elf.so.1 /usr/lib/crt1.o
/usr/lib/crti.o /usr/lib/crtbegin.o
-L/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0
-L/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/../../../../../x86_64-portbld-freebsd9.0/lib
-L/usr/local/lib/gcc47/gcc/x86_64-portbld-freebsd9.0/4.7.0/../../.. g.o -lgcc
--as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed
/usr/lib/crtend.o /usr/lib/crtn.o
GNU ld (GNU Binutils) 2.22
Supported emulations:
elf_x86_64_fbsd
elf_i386_fbsd
elf_x86_64
elf_i386
elf_l1om
elf_l1om_fbsd
elf_k1om
elf_k1om_fbsd
= the preprocessed file (*.i*) that triggers the bug, generated by adding
-save-temps to the complete compilation command
attached.
