[Bug libgcc/67379] New: libgcc2.c negation of -2147483648 cannot be represented in type 'int'

[zeccav at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67379

            Bug ID: 67379
           Summary: libgcc2.c negation of -2147483648 cannot be
                    represented in type 'int'
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: libgcc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zeccav at gmail dot com
  Target Milestone: ---

In libgcc2.c:1842

int m;
unsigned int n = m < 0 ? -m : m;

when m==-2147483648

I get the following message from the sanitizer

/home/vitti/gcc-5.2.0/libgcc/libgcc2.c:1842:31: runtime error: negation of
-2147483648 cannot be represented in type 'int'; cast to an unsigned type to
negate this value to itself

I suggest changing the line to the correct version

unsigned int n = m < 0 ? - (unsigned int) m : m;

to avoid undefinite behaviour

This is running the gfortran testsuite file integer_exponentiation_1.f90