Compilation issue when using blocks with LLVM GCC 4.2

Question

I wrote a gist a while ago: https://gist.github.com/611157. It compiled and worked ok.

I came back to it recently and it no longer complied.

I noticed it compiles with LLVM 2.0 with no problems or warnings (and then runs and works!)

With LLVM GCC 4.2 it fails to compile. I get the following error

error: incompatible block pointer types initializing 'signed char (^)(struct objc_object *, struct NSString *)', expected 'BOOL (^)(struct objc_object *, struct objc_object *)'

I have the feeling I have a declaration missing or wrong, but I don't know, so I thought I would ask.

Any ideas anyone?

Show your Block and variable declaration – Eiko Jun 28 '11 at 08:45 — Eiko, Jun 28 '11 at 08:45

score 2 · Accepted Answer · answered Jun 28 '11 at 09:35

The problem is that your block has type:

BOOL (^blockRelationship)(id,id)

but the second parameter in both the initialisation and the parameter type in the method declaration is NSString*

Change your block definition to

BOOL (^blockRelationship)(id,NSString*)=^(id obj,NSString* relationship) { ... } ;

I've tested the above in GCC 4.2, GCC 4.2 LLVM and Clang LLVM 1.6.

With the id second parameter, in the first two cases I got your error appearing on both the initialisation line and the line where it is passed as a parameter to toDictionaryBlockingRelationships: In the Clang case I got no error at all.

With NSString* as the second parameter, there were no errors in all three compilations.

Compilation issue when using blocks with LLVM GCC 4.2

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