> "gcc -ansi -Wall -Wextra -pedantic". NOT ONE ERROR OR WARNING! $ rpm -q gcc gcc-4.8.2-7.fc20.x86_64 $ gcc -ansi -Wall -Wextra -pedantic test.c test.c

> "gcc -ansi -Wall -Wextra -pedantic". NOT ONE ERROR OR WARNING! $ rpm -q gcc gcc-4.8.2-7.fc20.x86_64 $ gcc -ansi -Wall -Wextra -pedantic test.c test.c: In function ‘main’: test.c:7:36: warning: the comparison will always evaluate as ‘false’ for the address of ‘geteuid’ will never be NULL [-Waddress] if (getuid() != 0 && geteuid == 0) ^ If fact, just -Wall is enough to enable that warning. Maybe the coverage of -Waddress has changed since your version?