I'll take a look at the rest.  Have we rolled to this clang yet or do I need to build clang tot?

msarda@ can you take a look at auth error in the link above?

Our current clang has this, just off by default.

msarda@ it seems like the fix is to change the method param from `NSError **` --> `NSError *__autoreleasing*`

thakis@ does that sound correct?  Some light googling gave me conflicting advice, specifically: http://clang.llvm.org/docs/AutomaticReferenceCounting.html#indirect-parameters suggests NSError ** should "be implicitly qualified with __autoreleasing."

It appears this is the only error when adding -Wblock-capture-autoreleasing

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/48130024a853818d09b132c10dfca934a14e7da6

commit 48130024a853818d09b132c10dfca934a14e7da6
Author: thakis <thakis@chromium.org>
Date: Sat Feb 11 02:33:14 2017

clang: Disable -Wblock-capture-autoreleasing

This warning has existed for a while but used to be off-by-default.
Upstream made it on-by-default recently, which breaks the compile step
of the iOS ToT bot.

BUG= 691120 
TBR=hans

Review-Url: https://codereview.chromium.org/2682943010
Cr-Commit-Position: refs/heads/master@{#449837}

[modify] https://crrev.com/48130024a853818d09b132c10dfca934a14e7da6/build/config/compiler/BUILD.gn

justincohen: good point, let me look into that

Error looks like:

somefile.m: error: block captures an autoreleasing out-parameter, which may result in use-after-free bugs [-Werror,-Wblock-capture-autoreleasing]
          if (error) {
              ^
somefile.m: note: declare the parameter __autoreleasing explicitly to suppress this warning
- (NSDictionary *)fooWithError:(NSError **)error {
                                                  ^
                                                  __autoreleasing
somefile.m: note: declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools

asked at http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20170206/185128.html

Assigning to Justin as he said he would look into it.

thakis@ I'm not sure if the response here: http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20170206/185190.html implies we need to make a change (NSError ** -> NSError * __autoreleasing*) or that it's a clang bug.

I'm not sure either :-) I'll follow up there if I don't hear back by tomorrow.

I got a reply: http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20170213/185409.html

It sounds like clang does generate the code as if __autoreleasing is implicitly there at this point, but apparently this is surprising to people, so now clang warns when that happens. To suppress the warning, one has to explicitly add that __autoreleasing.

Does that make sense? Upstream is open to changing the wording of the warning if anyone has a better suggestion. But it sounds like we do want to add __autoreleasing to that file.

I landed the internal fix -- thakis@ can you try block-capture-autoreleasing again?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0f16147c62ef8635f594ed77c415cc9de2ece5a6

commit 0f16147c62ef8635f594ed77c415cc9de2ece5a6
Author: thakis <thakis@chromium.org>
Date: Mon Mar 06 18:29:28 2017

clang: Stop disabling -Wblock-capture-autoreleasing

Things should build with it enabled now, and it's a useful warning.

BUG= 691120 

Review-Url: https://codereview.chromium.org/2730273002
Cr-Commit-Position: refs/heads/master@{#454895}

[modify] https://crrev.com/0f16147c62ef8635f594ed77c415cc9de2ece5a6/build/config/compiler/BUILD.gn