Patch to fix IRGen crash using lambda expression as value in dictionary literal

[jahanian]

On Sep 16, 2014, at 4:46 PM, Reid Kleckner <rnk at google.com> wrote:

> This will have the observable effect of making cleanups run sooner, right? Can you test for that?

Yes. Generally, it now happens at the end of the ‘value’ part dictionary literal evaluation. While before it was happening at where
expression was considered a full expression (on return statement in this example). I am not sure if this change meshes well with
rules related to clean up code.

For this working test case:
id test()
{
   int cap_a, cap_b;
        return @{
                @"a": ^(){ cap_a; },
                @"b": ^(){ cap_b;}
        };
}

Before:
       `-ReturnStmt 0x7fde82076498 <line:20:9, line:23:9>
      `-ExprWithCleanups 0x7fde82076470 <line:20:16, line:23:9> 'id':'id'
        |-cleanup Block 0x7fde82076080
        |-cleanup Block 0x7fde82076270

With this patch:

    `-ReturnStmt 0x7ff2a10766a0 <line:20:9, line:23:9>
      `-ImplicitCastExpr 0x7ff2a1076688 <line:20:16, line:23:9> 'id':'id' <BitCast>
        `-ObjCDictionaryLiteral 0x7ff2a1076638 <line:20:16, line:23:9> 'NSDictionary *'
          |-ImplicitCastExpr 0x7ff2a1076580 <line:21:17, col:18> 'const id<NSCopying>' <BitCast>
          | `-ObjCStringLiteral 0x7ff2a1076258 <col:17, col:18> 'NSString *'
          |   `-StringLiteral 0x7ff2a1076200 <col:18> 'const char [2]' lvalue "a"
          |-ExprWithCleanups 0x7ff2a10765b0 <col:23, col:35> 'const id':'const id'
          | |-cleanup Block 0x7ff2a1076280
          | |-cleanup Block 0x7ff2a1076470


- fariborz


> 
> +// RUN: %clang_cc1 -triple x86_64-apple-darwin10.0.0 -emit-llvm -o - %s -fexceptions -std=c++11 -fblocks
> 
> If you aren't checking the IR, use -emit-llvm-only to avoid writing to stdout. However, IMO you should be checking the IR here.
> 
> On Tue, Sep 16, 2014 at 3:56 PM, jahanian <fjahanian at apple.com> wrote:
> Hi John,
> 
> This test case:
> 
> id test_dict()
> {
>         return @{
>                 @"a": [](){},
>                 @"b": [](){}
>         };
> }
> 
> Crashes in IRGen because ExprWithCleanups for the dummy BlockDecl we use to facilitate lambda to block conversion
> is at the wrong place.
> This happens because a lambda expression is considered a full expression so it calls MaybeCreateExprWithCleanups
> (see Sema::BuildBlockForLambdaConversion).
> which ends up adding the clean up code for the BlockDecl of the first lambda to the expression for the 2nd lambda!
> 
> Ideally, MaybeCreateExprWithCleanups should be called when the entire dictionary literal is seen. But in this case,
> this does not happen. Attached patch fixes this by making sure that after ‘every’ parse of the ‘value’ expression
> MaybeCreateExprWithCleanups is called. This, in effect, assumes that the ‘value’ literal is a full expression.
> I don’t know the ramification of this change in the common case as couple of non-lambda literal tests broke.
> (it now generates the none-exc version of call instead of exc versions in couple of places).
> 
> Please review. Let me know if you need additional info.
> 
> - Thanks, Fariborz
> 
> 
> 
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