[patch, libstdc++, testsuite] Modify tests to use tmpnam()

[Janis Johnson]

On Wed, 2010-03-03 at 16:51 -0800, Ian Lance Taylor wrote:
> Steve Ellcey <sje@cup.hp.com> writes:
> 
> > On Wed, 2010-03-03 at 14:57 -0800, Janis Johnson wrote:
> >
> >> I had forgotten that GNU ld warns about use of tmpnam:
> >> 
> >>    warning: the use of `tmpnam' is dangerous, better use `mkstemp'
> >> 
> >> It would be messy for the tests to turn off that warning since GNU ld
> >> isn't the only linker used with GCC.  Other tests that use tmpnam are
> >> compile-only and do not link.
> >> 
> >> Janis
> >
> > Is this warning triggered by some flag?  I ran the tests on Linux
> > systems as well as HP-UX ones and I didn't get any failures.  I also
> > don't see warnings in my log file.  The linux tests were done with the
> > ToT GNU linker.
> 
> The warning is issued by GNU ld and gold because glibc has a
> .gnu.warning.tmpnam section.  The contents of the section are the
> above text.  In other words, the warning is from glibc.
> 
> In the context of the libstdc++ testsuite, the warning could be pruned
> out by libstdc++-v3/testsuite/lib/prune.exp.
> 
> tmpnam is insecure in the sense that some other process can interpose
> a file between the time that tmpnam is called and the time that the
> file is created.  This problem is typically easily avoided by opening
> the file using the O_EXCL flag.
> 
> Ian

For this test it's better to just use a file name that's unique for the
testsuite, which was not the case.  Steve discovered that the warning
didn't affect test results, although it's not in prune.exp and I haven't
found out why it's ignored.

Janis