[Bug c/68081] New: Cygwin GCC cannot compile program that uses __builtin_ia32_rdseed64_step

["noloader at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68081

            Bug ID: 68081
           Summary: Cygwin GCC cannot compile program that uses
                    __builtin_ia32_rdseed64_step
           Product: gcc
           Version: 5.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: noloader at gmail dot com
  Target Milestone: ---

I'm testing on Cygwin64. Cygwin64 provides the 5.2.0 compiler.

Attempting to compile the following results in an error:

  $ cat rdseed.c
  #include <stdint.h>

  int main()
  {
    uint64_t val;
    __builtin_ia32_rdseed64_step(&val);
    return (int)val;
  }

The error is:

  $ gcc -mrdseed rdseed.c -o rdseed.exe
  ...
  rdseed.c:6:36: error: '__builtin_ia32_rdseed64_step' was not declared in this
scope.

The expected define appears to be defined:

  $ cpp -mrdseed -dM </dev/null | grep -i seed
  #define __RDSEED__ 1

The RDRAND equivalent compiles and executes.

-----

My apologies if this should be reported to Cygwin. I cannot find their bug
reporter. In fact, I can't even find a mailing list to discuss it. Their
mailing list page tells me where *not* to discuss or report bugs, but does not
state where to discuss or report them.