xs_arrays.c:247: warning: format not a string literal and no format arguments

Normally, gcc issues this warning if *printf functions are being called with a non-literal first argument, and the respective warnings are enabled. (See also -Wformat, -Wformat-nonliteral, -Wformat-security in the gcc man page)  For example

#include <stdio.h>
int main() {
    char foo[100];
    scanf("%s", foo);
    printf(foo);  /* compiler cannot inspect contents of foo */
    return 0;
}
[download]

$ gcc -Wformat -Wformat-security nonlit.c 
nonlit.c: In function 'main':
nonlit.c:5: warning: format not a string literal and no format argumen
+ts
[download]

It seems those warnings were enabled by default in gcc 4.2.1 (with my newer version I explicitly have to request them).

That said, I'm not sure where there would be something printf-related in your code... What is line 247?   Even the preprocessor expansion¹ of your snippet reveals no (s|f)printf whatsoever:

SV* vec_zeros(int m) {
    int i;
    AV *myav;
    SV **svs;

    (svs = ((void)(sizeof(SV *) > 1 && (m) > ((size_t)~0)/sizeof(SV *)
+ && (Perl_croak_nocontext(PL_memory_wrap),0)), (SV **)Perl_safesysmal
+loc((size_t)((m)*sizeof(SV *)))));

    for (i = 0; i < m; i++) {

        svs[i] = Perl_sv_newmortal(((PerlInterpreter *)pthread_getspec
+ific((*Perl_Gthr_key_ptr(((void *)0))))));

        Perl_sv_setnv(((PerlInterpreter *)pthread_getspecific((*Perl_G
+thr_key_ptr(((void *)0))))), (SV*)svs[i],0.0f);
    }

    myav = Perl_av_make(((PerlInterpreter *)pthread_getspecific((*Perl
+_Gthr_key_ptr(((void *)0))))), m,svs);

    Perl_safesysfree((void *)(svs));

    return Perl_newRV_noinc(((PerlInterpreter *)pthread_getspecific((*
+Perl_Gthr_key_ptr(((void *)0))))), (SV*) myav);
}
[download]

Anyhow, most likely, you can just ignore the warning, or disable it with -Wno-format.

___

¹ done with gcc option -E, on a Linux system, with a perl built with "usemymalloc=n" (like yours).