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adding reentrant to typedef function pointers causes redefinition in code

Robert Wilcox

I am porting some code to an 8051.

(header.h)

typedef int     (Writer) (int ,
                                   u_char * ,
                                   u_char ,
                                   size_t ,
                                   u_char * ,
                                   int *) reentrant;
(source.h)
Writer bob;

(source.c)
.
.
.
int     bob(int val1,
            u_char * dat1,
            u_char dat2,
            size_t val2,
            u_char * dat3,
            int *pval) reentrant
{
}

When I attempt to compiler this, I get
error C231: '_bob' : redefinition. If I go to source.h and do the following:
(source.h)
//Comment out Writer bob;
int     (bob)(int val1,
            u_char * dat1,
            u_char dat2,
            size_t val2,
            u_char * dat3,
            int *pval) reentrant;


It compiles fine. Is this a limitation of the compiler? Any shortcuts I could use so I don't have to rewrite large chunks of code

Parents
  • 0 in reply to HansBernhard Broeker

    The .h file provides a "prototype" of a function to be defined elsewhere. The redefinition warning means that when you actually define the function in the .c file, it does not match a previously seen declaration (typically in a .h file).

    While you've run into this problem with the reentrant attribute, it applies to any change in function signature. That is,

    .h:
    void MyFunction (long a);

    .c:
    void MyFunction (short a);

    would produce a redefinition warning.

    The .h file should always match the actual definition of the function, lest you confuse seperately-compiled callers.

Reply
  • 0 in reply to HansBernhard Broeker

    The .h file provides a "prototype" of a function to be defined elsewhere. The redefinition warning means that when you actually define the function in the .c file, it does not match a previously seen declaration (typically in a .h file).

    While you've run into this problem with the reentrant attribute, it applies to any change in function signature. That is,

    .h:
    void MyFunction (long a);

    .c:
    void MyFunction (short a);

    would produce a redefinition warning.

    The .h file should always match the actual definition of the function, lest you confuse seperately-compiled callers.

Children
  • 0 in reply to Drew Davis

    The .h file provides a "prototype" of a function to be defined elsewhere.

    That what it should do, for ordinary functions. But the case at hand is different, because

    Writer bob;
    is not a correct prototype declaration: the extern keyword is missing. As is, it's a tentative definition of a function object named "bob". I.e. every .c file this header is included in will have an (empty) function called bob inside. The linker complains about that, and it's right to do so.

    The redefinition warning means that when you actually define the function in the .c file, it does not match a previously seen declaration (typically in a .h file).

    No. For that you would get a "mismatch with previous declaration" warning/error from the compiler, not a redefinition complaint from the linker.

    The .h file should always match the actual definition of the function, lest you confuse seperately-compiled callers.

    Right. And the proper way of making sure of this is to always include the module's header file into its own .c file.

  • 0 in reply to HansBernhard Broeker

    "the proper way of making sure of this is to always include the module's header file into its own .c file."

    Yep - that's what I always say!