https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117208
Bug ID: 117208
Summary: Miscompilation at -O0
Product: gcc
Version: 11.4.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: jiajing_zheng at 163 dot com
Target Milestone: ---
Is this issue caused by the variable t in the main function being used without
initialization? However, the result of h = t is not utilized in the k function.
As shown below, test.c produces unexpected results when compiled with O0, but
outputs the correct result when compiled with O1, O2, O3, or Os.
$ cat test.c
#include <stdint.h>
#include <stdio.h>
struct {
int8_t a;
int8_t b;
} c[1] = {1, 255}, d = {1, 255};
int16_t e = 1;
int16_t *f = &e;
int16_t **g = &f;
int64_t h;
int16_t ***i = &g;
int16_t ****j = &i;
void k(int32_t *, uint32_t, int32_t, int64_t, int16_t) {}
void l(int64_t m) {
int8_t *n = &d.b;
int64_t *o = &h;
int64_t **p = &o;
int64_t ***q = &p;
if (!***q)
*n = m, ****j = 45289;
}
void main() {
int32_t *s;
int t;
k((l(3 && c), s), 0, 0, h = t, 0);
printf("%d\n", e);
printf("%d\n", d.b);
}
$ gcc test.c -O0 && ./a.out
1 -1
$ gcc test.c -O1 && ./a.out
-20247 1
$ gcc test.c -O2 && ./a.out
-20247 1
$ gcc test.c -O3 && ./a.out
-20247 1
$ gcc test.c -Os && ./a.out
-20247 1
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
11.4.0-1ubuntu1~22.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr
--with-gcc-major-version-only --program-suffix=-11
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes
--with-default-libstdcxx-abi=new --enable-gnu-unique-object
--disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib
--enable-libphobos-checking=release --with-target-system-zlib=auto
--enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet
--with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32
--enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-gcn/usr
--without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu
--host=x86_64-linux-gnu --target=x86_64-linux-gnu
--with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.4.0 (Ubuntu 11.4.0-1ubuntu1~22.04)
