[Sanitizer Common] Show command used to launch symbolizer process at high verbosity level.

[delcypher]

Summary

In preparation for writing a test for a bug fix we need to be able to
see the command used to launch the symbolizer process. This feature
will likely be useful for debugging how the Sanitizer's use the
symbolizer in general.

This patch causes the command line used to launch the process to be
shown at verbosity level 3 and higher.

A small test case is included.

[kubamracek]

Nice.

[yln]

compiler-rt/test/sanitizer_common/TestCases/symbolize_debug_argv.cpp

2

-USHARED_LIB: probably a refactoring leftover?

[delcypher]

compiler-rt/test/sanitizer_common/TestCases/symbolize_debug_argv.cpp

2

Oops yes. I'll fix that.

[delcypher]

Remove unneeded macro undefinition.

[delcypher]

@eugenis @vitalybuka @kcc Is it okay to land this?

[delcypher]

Tweak description.

compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cpp

if (!FileExists(path_)) {
     }
     return false;
   }
 
   const char *argv[kArgVMax];
   GetArgV(path_, argv);
   pid_t pid;
 
+  // Report how symbolizer is being launched for debugging purposes.
+  if (Verbosity() >= 3) {
+    // Only use `Report` for first line so subsequent prints don't get prefixed
+    // with current PID.
+    Report("Launching Symbolizer process: ");
+    for (unsigned index = 0; index < kArgVMax && argv[index]; ++index)
+      Printf("%s ", argv[index]);
+    Printf("\n");
+  }
+
   if (use_posix_spawn_) {
 #if SANITIZER_MAC
     fd_t fd = internal_spawn(argv, const_cast<const char **>(GetEnvP()), &pid);
     if (fd == kInvalidFd) {
       Report("WARNING: failed to spawn external symbolizer (errno: %d)\n",
              errno);
       return false;
     }

compiler-rt/test/sanitizer_common/TestCases/symbolize_debug_argv.cpp

+// RUN: %clangxx %s -g -o %t
+// RUN: %env_tool_opts=verbosity=3 %run %t 2>&1 | FileCheck %s
+#include <sanitizer/common_interface_defs.h>
+
+int main(int argc, char **argv) {
+  // CHECK: Launching Symbolizer process: {{.+}}
+  __sanitizer_print_stack_trace();
+  return 0;
+}