I tried playing with __builtin_constant_p and __builtin_choose_exp but they
have a very different notion of what a compile time constant is. ie. It's
something a literal or something declared const, _not_ something that is
known at compile time.
Even weirder.... The following compiles without warnings, but.....
#include <stdlib.h>#include <stdio.h>#include <assert.h>
static char __rangeCheckVariable;
#define asshurt(exp) \
do { \
char __rangeCheck[2]="a"; \
__rangeCheckVariable = \
__rangeCheck[(exp) ? 0 : 10]; \
} while(0)
void bunc( int i){
asshurt( i< 4);
assert( i<4);
printf( "%d\n",i);}
void func( int i){
bunc( i);}
int main( int argc __attribute__((unused)), char * argv[]
__attribute__((unused))){
int i = 10;
func( i);
return 0;}
Removed the line assert( i< 4); and you get
gcc -g3 -ggdb3 -O3 -W -Wall -Wextra -c d.c ;objdump -S d.o
d.c: In function ‘main’:
d.c:11:22: warning: array subscript is above array bounds [-Warray-bounds]
__rangeCheck[(exp) ? 0 : 10]; \
^
d.c:17:4: note: in expansion of macro ‘asshurt’
asshurt( i< 4);
^
ps: Sadly the strange things in the email disclaimer are auto added without
my consent.
--
John Carter
Phone : (64)(3) 358 6639
Tait Electronics
PO Box 1645 Christchurch
New Zealand
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