Allow $TMPDIR to set temporary directory on OS X.

base/files/file_util_mac.mm

Index: base/files/file_util_mac.mm
diff --git a/base/files/file_util_mac.mm b/base/files/file_util_mac.mm
index e9c6c651593571ca425c1a012db8ec76722938ff..8c97aec9803fc98aac8a448a89dae5876b3f4909 100644
--- a/base/files/file_util_mac.mm
+++ b/base/files/file_util_mac.mm
@@ -23,7 +23,13 @@ bool CopyFile(const FilePath& from_path, const FilePath& to_path) {
 }
 
 bool GetTempDir(base::FilePath* path) {
-  NSString* tmp = NSTemporaryDirectory();
+  // In order to facilitate hermetic runs on OS X, first check $TMPDIR

[Mark Mentovai, 2017/02/28 21:59:21]

“first check” makes it sound like TMPDIR might not be set, but it usually will
be set to the NSTemporaryDirectory. The comment should say so, otherwise it’s
kind of misleading.

[iannucci, 2017/03/01 02:22:21]

Actually now that I've thought about it a bit more... I'm guessing that it's
/NEVER/ set on iOS. Would it be worth an ifdef?

+  NSProcessInfo* procInfo = [NSProcessInfo processInfo];

[Mark Mentovai, 2017/02/28 21:59:20]

Meh. Just do

#include <stdlib.h>

  const char* env_tmpdir = getenv("TMPDIR");
  if (env_tmpdir) {
    *path = base::FilePath(env_tmpdir);
    return true;
  }

because that’s what NSProcessInfo is going to do under the hood anyway, and it’s
way less work to just do the getenv() compared to creating all sorts of objects
and allocating all sorts of memory and doing all sorts of string conversions
when the thing we really want is just the raw const char* to stick into a
FilePath’s std::string.

[iannucci, 2017/03/01 02:22:21]

That was actually my first instinct, but I wasn't sure what was preferred.

+  NSString* tmp = [[procInfo environment] objectForKey: @"TMPDIR"];
+  if (tmp == nil) {
+    // Then fallback to the immutable NSTemporaryDirectory value.

[Nico, 2017/02/27 01:16:20]

nit: "fallback" is a noun, "fall back" is the verb

[Mark Mentovai, 2017/02/28 21:59:20]

Fix this :)

[iannucci, 2017/03/01 02:22:21]

Done.

+    tmp = NSTemporaryDirectory();
+  }
   if (tmp == nil)
     return false;
   *path = base::mac::NSStringToFilePath(tmp);