[fpc-pascal] Mac osx callback functions parameters: wrong values in 386 mode.

Jonas Maebe jonas.maebe at elis.ugent.be
Mon Sep 6 18:13:05 CEST 2010

On 06 Sep 2010, at 17:21, fpanasiti at tiscali.it wrote:

> Using control callback function with a control (a button) apparently 
> results in wrong 
> parameter values when compiling to 386 (values are correct compiling 
> to ppc).

The default calling convention on non-i386 platforms is mostly the same as the C calling convention. On i386, it's different for Delphi compatibility. Add the "mwpascal;" modifier at the end of the function declaration to get the same calling convention behaviour as with MetroWerks Pascal (that's also the calling convention expected by the declarations in the macosall unit).

>    lControlActionUPP:= NewControlActionUPP(ControlActionProcPtr
> (@myActionProc));

By adding an explicit typecast you make it impossible for the compiler to tell you that the routines are incompatible. Remove the ControlActionProcPtr typecast, and if you are using MacPas mode then also remove the "@". The compiler will then give an error if the callback's signature is wrong, and it will also print the signature of the expected type.


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