Define _PTHREADS for -pthread on NetBSD

[krytarowski]

Summary

GCC and PCC define _PTHREADS for -pthreads
on NetBSD.

The _PTHREADS preprocessor macro is used in
the NetBSD header in <stdio.h>.

NetBSD uses both: _REENTRANT and _PTHREAD
for the -pthreads command line option.

Sponsored by <The NetBSD Foundation>

[krytarowski]

As discussed with Joerg, _PTHREADS is considered legacy and we can bear with lack of it and inconsistency with GCC.

lib/Basic/Targets/OSTargets.h

 class LLVM_LIBRARY_VISIBILITY NetBSDTargetInfo : public OSTargetInfo<Target> {
 protected:
   void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
                     MacroBuilder &Builder) const override {
     // NetBSD defines; list based off of gcc output
     Builder.defineMacro("__NetBSD__");
     Builder.defineMacro("__unix__");
     Builder.defineMacro("__ELF__");
-    if (Opts.POSIXThreads)
+    if (Opts.POSIXThreads) {
       Builder.defineMacro("_REENTRANT");
+      Builder.defineMacro("_PTHREADS");
+    }
   }
 
 public:
   NetBSDTargetInfo(const llvm::Triple &Triple, const TargetOptions &Opts)
       : OSTargetInfo<Target>(Triple, Opts) {
     this->MCountName = "_mcount";
   }
 };

test/Driver/netbsd.c

 // S-POWERPC64: ld{{.*}}" "--eh-frame-hdr" "-Bstatic"
 // S-POWERPC64: "-m" "elf64ppc"
 // S-POWERPC64: "-o" "a.out" "{{.*}}/usr/lib{{/|\\\\}}crt0.o"
 // S-POWERPC64: "{{.*}}/usr/lib{{/|\\\\}}crti.o"
 // S-POWERPC64: "{{.*}}/usr/lib{{/|\\\\}}crtbegin.o" "{{.*}}.o" "-lc"
 // S-POWERPC64: "{{.*}}/usr/lib{{/|\\\\}}crtend.o" "{{.*}}/usr/lib{{/|\\\\}}crtn.o"
 
 // PTHREAD-NOT: _POSIX_THREADS
+// PTHREAD:     _PTHREADS
 // PTHREAD:     _REENTRANT
 // PTHREAD-NOT: _POSIX_THREADS