Indeed, and if you use -Wall -Wextra -ansi -pedantic you get: pointer-test.c:7:3: warning: format ‘%p’ expects type ‘void * ’, but argument 2 has type ‘int * ’

Indeed, and if you use -Wall -Wextra -ansi -pedantic you get: pointer-test.c:7:3: warning: format ‘%p’ expects type ‘void * ’, but argument 2 has type ‘int * ’ Same goes for using -std=c99 instead of -ansi, although casting to (void *) does get rid of the warning.