c - Pointer to a function that accepts both const and non-const arguments -

i want write wrapper read , write unix functions, read has const void pointer parameter, , write simple void pointer parameter.

so, prototype this, fail 1 of functions:

typedef ssize_t (*genericstreamhandler)(int, const void*, size); 

do not prototype function signature if code needs allow incompatible functions.

the following compiles without warnings/errors.

#include <stdio.h>  ssize_t file_read(int h, const void* b, int sz) {   if (b) return 0;   return h + sz; }  ssize_t file_write(int h, void* b, int sz) {   if (b) return 0;   return h + sz; }  //typedef ssize_t (*genericstreamhandler)(int, void*, int); //                                      v--- no function prototype typedef ssize_t (*genericstreamhandler)();  int main(void) {   genericstreamhandler gfh1 = file_read;   genericstreamhandler gfh2 = file_write;   char buf[10];   return (*gfh1)(0, buf, 10) + (*gfh2)(0, buf, 10); } 

otoh, better answer may lie in taking approach not need common type variant function signatures.