Re: M4 tests fail when built with PGI compilers

[Paul Eggert]

On 01/30/2017 02:39 PM, Eric Blake wrote:
> > I don't think test-intprops.c is compatible with the PGI compilers.

Yes, test-intprops.c runs afoul of a problem in the PGI compiler. I can 
reproduce the problem in PGI 16.10 x86-64 by compiling this one-line 
program:

  short bar = -32768 <= 100000 && 100000 <= 32767  ? (short) 100000 : 0;

Although this is valid C code and is well-defined to initialize 'bar' to 
0 on x86-64, pgcc warns "Constant value out of range for signed short or 
char". Since the expression "(short) 100000" is not evaluated, the 
warning is bogus. Although PGI generates thousands of similar warnings 
for test-intprops.c, I expect that they are all bogus and that you can 
ignore them. As 'make check' does not fail and I don't see an easy way 
to suppress the bogus warnings, I suspect we ought to leave the code alone.

Admittedly these warnings are annoying. Adam, since you're a PGI user, 
perhaps you could report the compiler bug or bugs to the PGI maintainers.

While I was at it, I looked at the other warnings that PGI generates for 
GNU M4, and managed to silence most of the rest with this Gnulib patch:

http://git.savannah.gnu.org/cgit/gnulib.git/commit/?id=16f6a8d8d81cc93745a24c0fb89caab2c383ae3c

A half-dozen or so of the thousands of Gnulib warnings were actual 
portability bugs in Gnulib, which made the exercise worth doing I 
suppose. I don't think these bugs affect GNU M4.