null pointers [LWN.net]

null pointers

Posted Mar 19, 2008 10:13 UTC (Wed) by cortana (subscriber, #24596)
In reply to: null pointers by tialaramex
Parent article: Who maintains dpkg?

I wonder... is that a -W option to GCC that enables a warning if you try to pass NULL or 0 to
a varargs function where a pointer to some data is expected?

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null pointers

Posted Mar 20, 2008 10:22 UTC (Thu) by msmeissn (subscriber, #13641) [Link]

If you mark up the function with __attribute__((sentinel)) then
it will warn.

All common functions are marked up already.

$ cat xx.c
#include <unistd.h>

void f() {
        execl("hello","world","!",0);
}
$ gcc -Wall -O2 -c xx.c 
xx.c: In function &#8216;f&#8217;:
xx.c:4: warning: missing sentinel in function call
$ 

I personally marked up X, GLIB and GTK for instance... :/

Ciao, Marcus

null pointers

Posted Mar 22, 2008 17:03 UTC (Sat) by spitzak (subscriber, #4593) [Link]

Aha! So that's what that damn warning means!

It would really help if the warning said "missing cast of 0 to varargs function" rather than
"missing sentinal"!