[Bug analyzer/109577] -Wanalyzer-allocation-size mishandles __builtin_mul_overflow

[eggert at cs dot ucla.edu via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109577

Paul Eggert <eggert at cs dot ucla.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |eggert at cs dot ucla.edu

--- Comment #1 from Paul Eggert <eggert at cs dot ucla.edu> ---
I ran into the same problem with gcc (GCC) 13.1.1 20230426 (Red Hat 13.1.1-1)
but I don't know how to update the version number in Bugzilla.

Also, I came up with the following simpler test case. Compile this with "gcc
-O2 -S -fanalyzer foo.c", and it will complain "allocated buffer size is not a
multiple of the pointee's size" in the function "safer", but it will not
complain about the function "unsafe" (which, unlike "safer", does not check for
integer overflow and so is less safe).

void *malloc (unsigned long);

double *
unsafe (unsigned long n)
{
  return malloc (n * sizeof (double));
}

double *
safer (unsigned long n)
{
  unsigned long nbytes;
  if (__builtin_mul_overflow (n, sizeof (double), &nbytes))
    return 0;
  return malloc (nbytes);
}