[Bug c/120966] New: -Waggressive-loop-optimizations warns for int but not for short overflow

[tvijlbrief at gmail dot com]

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.