Allow $TMPDIR to set temporary directory on OS X.

base/files/file_util_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/files/file_util.h"
 
 #include <copyfile.h>
 #import <Foundation/Foundation.h>
 
 #include "base/files/file_path.h"
 #include "base/mac/foundation_util.h"
 #include "base/strings/string_util.h"
 #include "base/threading/thread_restrictions.h"
 
 namespace base {
 
 bool CopyFile(const FilePath& from_path, const FilePath& to_path) {
   ThreadRestrictions::AssertIOAllowed();
   if (from_path.ReferencesParent() || to_path.ReferencesParent())
     return false;
   return (copyfile(from_path.value().c_str(),
                    to_path.value().c_str(), NULL, COPYFILE_DATA) == 0);
 }
 
 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);
   return true;
 }
 
 FilePath GetHomeDir() {
   NSString* tmp = NSHomeDirectory();
   if (tmp != nil) {
     FilePath mac_home_dir = base::mac::NSStringToFilePath(tmp);
     if (!mac_home_dir.empty())
       return mac_home_dir;
   }
 
   // Fall back on temp dir if no home directory is defined.
   FilePath rv;
   if (GetTempDir(&rv))
     return rv;
 
   // Last resort.
   return FilePath("/tmp");
 }
 
 }  // namespace base