Question

See I have made a library which has several .h & several .c files.

Now under some circumstances I have not removed a warning that says

warning: implicit declaration of function ‘getHandle’

Now I want to ask you, does this cause any problem in the binary of my library?

Will it negatively affect the execution of my library on embedded platforms or anywhere else?

Answer 1

In such a case the compiler cannot verify that the usage of getHandle is proper – that is, whether the return value and the arguments are of the right type and count. It will just accept the way you call it without any explicit statement that this is the right way.

Adding a prototype of the function is a way to tell the compiler that this is the intended usage of the function and it will be a compile-time error not to comply to that.

It may cause some nasty bugs in case there is a mismatch between the way it’s called and the way the function expects its arguments. The most likely effect will be a corruption of the stack.

If there isn’t a mismatch, it won’t make any difference at runtime.