Try to use /proc on FreeBSD for getExecutablePath

Currently, clang's libTooling passes this function a fake argv0, which
means that no libTooling tools can find the standard headers on FreeBSD.
With this change, these will now work on any FreeBSD systems that have
procfs mounted.  This isn't the right fix for the libTooling issue, but
it does bring the FreeBSD implementation of getExecutablePath closer to
the Linux and macOS implementations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@359427 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Support/Unix/Path.inc b/lib/Support/Unix/Path.inc
index 0e150d1ac2698f27866a552f2c30ae807722c008..fa5115bfd6517b1bd8ada935d732d531394291bc 100644 (file)
--- a/lib/Support/Unix/Path.inc
+++ b/lib/Support/Unix/Path.inc
@@ -185,8 +185,21 @@ std::string getMainExecutable(const char *argv0, void *MainAddr) {
 #elif defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||   \
     defined(__minix) || defined(__DragonFly__) ||                              \
     defined(__FreeBSD_kernel__) || defined(_AIX)
+  StringRef curproc("/proc/curproc/file");
   char exe_path[PATH_MAX];
-
+  // /proc is not mounted by default under FreeBSD, but gives more accurate
+  // information than argv[0] when it is.
+  if (sys::fs::exists(curproc)) {
+    ssize_t len = readlink(curproc.str().c_str(), exe_path, sizeof(exe_path));
+    if (len > 0) {
+      // Null terminate the string for realpath. readlink never null
+      // terminates its output.
+      len = std::min(len, ssize_t(sizeof(exe_path) - 1));
+      exe_path[len] = '\0';
+      return exe_path;
+    }
+  }
+  // If we don't have procfs mounted, fall back to argv[0]
   if (getprogpath(exe_path, argv0) != NULL)
     return exe_path;
 #elif defined(__linux__) || defined(__CYGWIN__)