[PATCH] Add -Warc-implicit-writeback

[Timothy Wood]

http://llvm.org/bugs/show_bug.cgi?id=19009

Split out from http://llvm.org/bugs/show_bug.cgi?id=15649


In some cases, ARC implicit writeback can result in loss of what the user likely intended. For example:

    int main(int argc, char *argv[])
    {
        __block id value = @"initial value";
        void (^block)(id *outValue) = ^(id *outValue){
            value = @"hello";
        };
        block(&value);
        NSLog(@"value = %@", value);
        return 0;
    }

With ARC, this reports:

    2013-04-24 13:55:35.814 block-local-address[28013:707] value = initial value

but with MRR:

    2013-04-24 13:57:26.058 block-local-address[28046:707] value = hello

Attached is a patch vs trunk r202532 that adds -Warc-implicit-writeback and test cases for the ObjC and ObjC++ compilers (which each seem to have their own support for writeback).

-------------- next part --------------
A non-text attachment was scrubbed...
Name: warn-arc-implicit-writeback.patch
Type: application/octet-stream
Size: 4511 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20140228/0a1b130e/attachment.obj>
-------------- next part --------------