These days it's safe to assume support for function prototypes (introduced in C89).
Functions that test programs declare should also be conditionalized for C++, which requires ‘extern "C"’ prototypes. Make sure to not include any header files containing clashing prototypes.
#ifdef __cplusplus
extern "C"
#endif
void *valloc (size_t);
If a test program calls a function with invalid parameters (just to see
whether it exists), organize the program to ensure that it never invokes
that function. You can do this by calling it in another function that is
never invoked. You can't do it by putting it after a call to
exit, because GCC version 2 knows that exit
never returns
and optimizes out any code that follows it in the same block.
If you include any header files, be sure to call the functions
relevant to them with the correct number of arguments, even if they are
just 0, to avoid compilation errors due to prototypes. GCC
version 2
has internal prototypes for several functions that it automatically
inlines; for example, memcpy. To avoid errors when checking for
them, either pass them the correct number of arguments or redeclare them
with a different return type (such as char).