[llvm] r355283 - [llvm] [Support] Reimplement getMainExecutable() using sysctl on NetBSD

[Michal Gorny via llvm-commits]

Author: mgorny
Date: Sun Mar  3 02:06:40 2019
New Revision: 355283

URL: http://llvm.org/viewvc/llvm-project?rev=355283&view=rev
Log:
[llvm] [Support] Reimplement getMainExecutable() using sysctl on NetBSD

Use sysctl() to implement getMainExecutable() on NetBSD, rather than
trying to guess the correct path from argv[0].  This is one
of the fixes to recent clang-check-mac-libcxx-fixed-compilation-db.cpp
test failure on NetBSD.

This has been historically done on both FreeBSD and NetBSD in r303015,
and reverted in r303285 due to buggy implementation on FreeBSD.
However, FWIK the NetBSD implementation does not suffer from the same
bugs and is more reliable than playing with argv[0].

Differential Revision: https://reviews.llvm.org/D56975

Modified:
    llvm/trunk/lib/Support/Unix/Path.inc

Modified: llvm/trunk/lib/Support/Unix/Path.inc
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/Unix/Path.inc?rev=355283&r1=355282&r2=355283&view=diff
==============================================================================
--- llvm/trunk/lib/Support/Unix/Path.inc (original)
+++ llvm/trunk/lib/Support/Unix/Path.inc Sun Mar  3 02:06:40 2019
@@ -90,6 +90,11 @@
 #define STATVFS_F_FLAG(vfs) (vfs).f_flags
 #endif
 
+#if defined(__NetBSD__)
+#include <sys/param.h>
+#include <sys/sysctl.h>
+#endif
+
 using namespace llvm;
 
 namespace llvm {
@@ -98,7 +103,7 @@ namespace fs {
 
 const file_t kInvalidFile = -1;
 
-#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||     \
+#if defined(__FreeBSD__) || defined(__OpenBSD__) ||     \
     defined(__minix) || defined(__FreeBSD_kernel__) || defined(__linux__) ||   \
     defined(__CYGWIN__) || defined(__DragonFly__) || defined(_AIX) || defined(__GNU__)
 static int
@@ -169,7 +174,18 @@ std::string getMainExecutable(const char
     if (realpath(exe_path, link_path))
       return link_path;
   }
-#elif defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) ||   \
+#elif defined(__NetBSD__)
+  // NB: sysctl() solution can't be used on FreeBSD since it may return
+  // a wrong path when a file is hardlinked in multiple locations.
+  // See r303285 for an earlier revert.
+
+  char exe_path[PATH_MAX];
+  int mib[4] = {CTL_KERN, KERN_PROC_ARGS, -1, KERN_PROC_PATHNAME};
+  size_t len = sizeof(exe_path);
+
+  if (sysctl(mib, 4, exe_path, &len, nullptr, 0) == 0)
+    return exe_path;
+#elif defined(__FreeBSD__) || defined(__OpenBSD__) ||   \
     defined(__minix) || defined(__DragonFly__) ||                              \
     defined(__FreeBSD_kernel__) || defined(_AIX)
   char exe_path[PATH_MAX];