[Bug fortran/118862] New: UBSAN: shift exponent too large since r15-7345-gc2a0ee58865c5a

[jamborm at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118862

            Bug ID: 118862
           Summary: UBSAN: shift exponent too large since
                    r15-7345-gc2a0ee58865c5a
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: fortran
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jamborm at gcc dot gnu.org
                CC: tkoenig at gcc dot gnu.org
            Blocks: 63426
  Target Milestone: ---
              Host: x86_64-linux
            Target: x86_64-linux

With UBSAN instrumented compiler (revision ), compiling the
testcase gfortran.dg/unsigned_44.f90 at -O3 fails with:

 
/home/worker/buildworker/tiber-gcc-ubsan/build/gcc/fortran/trans-expr.cc:3650:44:
runtime error: shift exponent 127 is too large for 64-bit type 'long unsigned
int'

To configure the compiler with UBSAN, bootstrap it with option
--with-build-config=bootstrap-ubsan (we also only do release
checking).

I have bisected the failure to r15-7345-gc2a0ee58865c5a (Thomas
Koenig: Add modular exponentiation for UNSIGNED.)


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63426
[Bug 63426] [meta-bug] Issues found with -fsanitize=undefined