Assert Implicit Declaration or Non-existent Functions

[ruzip]

or functions that does not exists..

Is there a way to do an assert on C (particularly) so if a function does not exist (implicit declaration) AND undefined symbol, I can assert it with a different message?

[salem c]

gcc has this to fix the first part.

-Wimplicit-function-declaration (C and Objective-C only)
Give a warning whenever a function is used before being declared. In C99 mode (-std=c99 or -std=gnu99), this warning is enabled by default and it is made into an error by
-pedantic-errors. This warning is also enabled by -Wall.

But undefined symbols are only known at link time.
Specifically at the end of the linker when it's loaded all the object files and searched all the libraries.

[ruzip]

Thanks. I was also looking for an example using assert.