implicit declaration warning: What are the built-in functions?
问题 The question-asking interface is flagging many "Questions that may already have your answer", but I have attempted to do due diligence to check if any are asking exactly what I am here. My apologies if this is a duplicate. Suppose I have the following incorrect program: extern void undefined_function(void); int main(int argc, char **argv) { undefined_function(); undeclared_function(); exit(0); } Compiling with gcc gives: $ gcc warnings.c warnings.c: In function ‘main’: warnings.c:6:2: warning