https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120966
Bug ID: 120966
Summary: -Waggressive-loop-optimizations warns for int but not
for short overflow
Product: gcc
Version: 13.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: tvijlbrief at gmail dot com
Target Milestone: ---
=====undef.c=========
int sum;
int main()
{
short s= 1;
while (s) {
s++;
sum += s;
}
int i= 1;
while (i) {
i++;
sum += i;
}
}
======
$ gcc -O2 undef.c
undef.c: In function ‘main’:
undef.c:13:6: warning: iteration 2147483646 invokes undefined behavior
[-Waggressive-loop-optimizations]
13 | i++;
| ~^~
undef.c:12:10: note: within this loop
12 | while (i) {
| ^
===========
gcc should give the same warning for the short integer s.
Note that this report is generated on a Linux system with 32bit int and 16bit
short:
tom@swan-ubu20:~/src/rust/arduino-hal-test/bug$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-linux-gnu/13/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
13.3.0-6ubuntu2~24.04' --with-bugurl=file:///u
sr/share/doc/gcc-13/README.Bugs
--enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=/usr --wit
h-gcc-major-version-only --program-suffix=-13
--program-prefix=x86_64-linux-gnu- --enable-shared --enable-lin
ker-build-id --libexecdir=/usr/libexec --without-included-gettext
--enable-threads=posix --libdir=/usr/lib --
enable-nls --enable-bootstrap --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --wit
h-default-libstdcxx-abi=new --enable-libstdcxx-backtrace
--enable-gnu-unique-object --disable-vtable-verify -
-enable-plugin --enable-default-pie --with-system-zlib
--enable-libphobos-checking=release --with-target-syst
em-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror
--enable-cet --with-arch-32=i686 --wit
h-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib
--with-tune=generic --enable-offload-targets=nv
ptx-none=/build/gcc-13-fG75Ri/gcc-13-13.3.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-13-fG75Ri/gcc-13-13
.3.0/debian/tmp-gcn/usr --enable-offload-defaulted --without-cuda-driver
--enable-checking=release --build=x8
6_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
--with-build-config=bootstrap-lto-lean --ena
ble-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 13.3.0 (Ubuntu 13.3.0-6ubuntu2~24.04)
But the same issue is present with avr-gcc version 14, which has 16 bit int and
16 bit short.
