[Bug libstdc++/56475] New: Incorrect result of configure test for /dev/random (_GLIBCXX_USE_RANDOM_TR1) for MinGW platform (and others?)

[k2k at narod dot ru]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56475

             Bug #: 56475
           Summary: Incorrect result of configure test for /dev/random
                    (_GLIBCXX_USE_RANDOM_TR1) for MinGW platform (and
                    others?)
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: k2k@narod.ru
              Host: mingw32
            Target: mingw32, mingw32-w64


When building native compiler for MinGW/MinGW-w64 'configure' checks for
/dev/random simply by 

    if test -r /dev/random && test -r /dev/urandom; then
      glibcxx_cv_random_tr1=yes;
    else
      glibcxx_cv_random_tr1=no;
    fi

Result of this test is incorrect at least for MinGW. MinGW shell is executed in
MSYS subsystem, so those devices is available for shell, but MinGW compiled
programs will have no access to /dev/random.
For some other platforms situation can be the same (/dev/random available for
shell, but not for compiled program).

I suggest to do a real compile-link-execute test instead of weak shell
emulation.