Preprocessor and sizeof()

Discussion in 'C' started by Amigo, Sep 30, 2006.

  1. Amigo

    Amigo New Member

    Sep 30, 2006
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    Hello all!

    I started working on an embedded project a few ago on Freescale 16-bit micro with an IAR toolset. Running PolySpace for the project code highlighted amongst other things a peculiar construct in one of the compiler's header files. Here's the code snippet:

    #ifndef __SIZE_T_TYPE__
    #if sizeof((char*)0 - (char*)0) <= sizeof(int)
    #define __SIZE_T_TYPE__ unsigned int
    #define __SIZE_T_TYPE__ unsigned long

    I was very suspicious about this construct in the first place, but coming from a compiler vendor baffled me even more. Although I kind of understand what the author wanted, the combination of sizeof and pre-processing is bound to not comply with the ANSI C specification.

    My question is: have you ever encountered such a construct in a file delivered by a tool vendor? It definitely "works", in that the compiler does not throw errors or warnings. But because this code goes into a safety-related project I need to understand exactly what's happening in the code and why. Any thoughts appreciated.


    PS: I was dumped in the project team just last week, so I did not have time to look through the whole of the project (documentation is
    "standard", i.e. poor)

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