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The option tables of the various fftools (in particular ffprobe) are arrays of OptionDef; said type contains a union of a pointer to void and a function pointer of type int (*)(void *, const char *, const char *) as well as a size_t. Some entries (namely the common entry for writing a report as well as several more of ffprobe's entries) used the pointer to void to store a pointer to functions of type int (*)(const char *) or type int (*)(const char *, const char *); nevertheless, when the functions are actually called in write_option (in cmdutils.c), it is done via a pointer of the first type. There are two things wrong here: 1. Pointer to void can be converted to any pointer to incomplete or object type and back; but they are nevertheless not completely generic pointers: There is no provision in the C standard that guarantees their convertibility with function pointers. C90 lacks a generic function pointer, C99 made every function pointer a generic function pointer and still disallows the convertibility with void *. 2. The signature of the called function differs from the signature of the pointed-to type. This is undefined behaviour in C99 (given that C90 lacks a way to convert function pointers at all, it doesn't say anything about such a situation). It only works because none of the functions this patch is about make any use of their parameters at all. Therefore this commit changes the type of the relevant functions to match the type used for the call and uses the union's function pointer to store it. This is legal even in C90. Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> Reviewed-by: Paul B Mahol <onemda@gmail.com> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>tags/n4.3
Andreas Rheinhardt
Michael Niedermayer
5 years ago