[SystemZ][ZOS] Implement getMainExecutable() and is_local_impl()

[Kai]

Summary

Adds implementation of getMainExecutable() and is_local_impl() to Support/Unix/Path.inc.
Both are needed to compile LLVM for z/OS.

[emaste]

some nitpick comments. I'm not familiar with z/OS's APIs here so not qualified to fully review the change in getMainExecutable but seems reasonable

llvm/lib/Support/Unix/Path.inc

55

this should probably be part of the #ifdef/#elif block?

70

Maybe this?

#if !defined(PATH_MAX)
# if defined(__GNU__)
#  define PATH_MAX 4096
# elif defined(__MVS__)
#  define PATH_MAX _XOPEN_PATH_MAX
# endif
#endif

[Kai]

• Moved the first #if defined(__MVS__) into the if/elif casecade right above
• Rearranged the #if !defined(PATH_MAX) guarded section

[hubert.reinterpretcast]

llvm/lib/Support/Unix/Path.inc

62–63

Minor nit: The comment placement is awkward here. It would work just find inside the __GNU__ block.

[Kai]

• Moved comment inside #if defined(__GNU__)

[hubert.reinterpretcast]

LGTM; thanks.

llvm/lib/Support/Unix/Path.inc

 #if __FreeBSD_version >= 1300057
 #include <sys/auxv.h>
 #else
 #include <machine/elf.h>
 extern char **environ;
 #endif
 #elif defined(__DragonFly__)
 #include <sys/mount.h>
+#elif defined(__MVS__)
+#include <sys/ps.h>
 #endif
 
 // Both stdio.h and cstdio are included via different paths and
 // stdcxx's cstdio doesn't include stdio.h, so it doesn't #undef the macros
 // either.
 #undef ferror
 #undef feof
 
+#if !defined(PATH_MAX)
 // For GNU Hurd
-#if defined(__GNU__) && !defined(PATH_MAX)
-# define PATH_MAX 4096
+#if defined(__GNU__)
+#define PATH_MAX 4096
+#elif defined(__MVS__)
+#define PATH_MAX _XOPEN_PATH_MAX
+#endif
 #endif
 
 #include <sys/types.h>
 #if !defined(__APPLE__) && !defined(__OpenBSD__) && !defined(__FreeBSD__) &&   \
     !defined(__linux__) && !defined(__FreeBSD_kernel__) && !defined(_AIX)
 #include <sys/statvfs.h>
 #define STATVFS statvfs
 #define FSTATVFS fstatvfs
 #define STATVFS_F_FRSIZE(vfs) vfs.f_frsize
 #else
 #if defined(__OpenBSD__) || defined(__FreeBSD__)

 #else
 #include <sys/mount.h>
 #endif
 #define STATVFS statfs
 #define FSTATVFS fstatfs
 #define STATVFS_F_FRSIZE(vfs) static_cast<uint64_t>(vfs.f_bsize)
 #endif
 
-#if defined(__NetBSD__) || defined(__DragonFly__) || defined(__GNU__)
+#if defined(__NetBSD__) || defined(__DragonFly__) || defined(__GNU__) || \
+    defined(__MVS__)
 #define STATVFS_F_FLAG(vfs) (vfs).f_flag
 #else
 #define STATVFS_F_FLAG(vfs) (vfs).f_flags
 #endif
 
 using namespace llvm;
 
 namespace llvm {
#else
     char real_path[PATH_MAX];
     if (realpath(exe_path, real_path))
       return std::string(real_path);
 #endif
   }
   // Fall back to the classical detection.
   if (getprogpath(exe_path, argv0))
     return exe_path;
+#elif defined(__MVS__)
+  int token = 0;
+  W_PSPROC buf;
+  char exe_path[PS_PATHBLEN];
+  pid_t pid = getpid();
+
+  memset(&buf, 0, sizeof(buf));
+  buf.ps_pathptr = exe_path;
+  buf.ps_pathlen = sizeof(exe_path);
+
+  while (true) {
+    if ((token = w_getpsent(token, &buf, sizeof(buf))) <= 0)
+      break;
+    if (buf.ps_pid != pid)
+      continue;
+    char real_path[PATH_MAX];
+    if (realpath(exe_path, real_path))
+      return std::string(real_path);
+    break;  // Found entry, but realpath failed.
+  }
 #elif defined(HAVE_DLFCN_H) && defined(HAVE_DLADDR)
   // Use dladdr to get executable path if available.
   Dl_info DLInfo;
   int err = dladdr(MainAddr, &DLInfo);
   if (err == 0)
     return "";
 
   // If the filename is a symlink, we need to resolve and return the location of
while (Ret--) {
     if (memcmp(&Vfs.f_fsid, &Vp->vmt_fsid, sizeof Vfs.f_fsid) == 0)
       return (Vp->vmt_flags & MNT_REMOTE) == 0;
 
     CurObjPtr += Vp->vmt_length;
   }
 
   // vmount entry not found; "remote" is the conservative answer.
   return false;
+#elif defined(__MVS__)
+  // The file system can have an arbitrary structure on z/OS; must go with the
+  // conservative answer.
+  return false;
 #else
   return !!(STATVFS_F_FLAG(Vfs) & MNT_LOCAL);
 #endif
 }
 
 std::error_code is_local(const Twine &Path, bool &Result) {
   struct STATVFS Vfs;
   if (::STATVFS(const_cast<char *>(Path.str().c_str()), &Vfs))