warning: implicit declaration of function ‘getresuid’ (and ‘seteuid’)

Question

I would like to get rid of the warnings. When I compile the source code with

gcc -Wall -ansi -o test test.c  

I get back

te         


        

Answer 1

getresuid() and seteuid() are GNU extension function, add

#define _GNU_SOURCE

before including all the headers, or add -D_GNU_SOURCE in GCC options.

You shouldn't define __USE_GNU macro directly, it's supposed to be used only internally in glibc.

Answer 2

I solved by adding #include <unistd.h>