------- Additional Comments From gcc at sopwith dot solgatos dot com
2005-03-15 23:22 -------
I observe that gcc -Wconversion generates the exact same warning
message for converting from narrow to wide as it does for converting
from wide to narrow. Correct me if I'm wrong, but converting from
narrow to wide should always be safe, while converting from wide to
narrow is not safe. I would like to be able to find the unsafe
conversions without drowning in warning messages about safe conversions.
This would make porting code from ILP32 to LP64 easier.
sopwith cat conversion2.c
#include <stdio.h>
void func1(int);
void func2(long);
int
main(void)
{
long a;
func1(5);
func2(5); /* line 12 - conversion appears to be harmless? */
a = 5;
func1(a); /* line 15 - conversion appears to be harmless? (since the data fits
in 32 bits) */
func2(a);
a = 50000000000;
func1(a); /* line 19 - conversion throws away data */
func2(a);
return 0;
}
void
func1(int arg)
{
printf("func1: arg = %d\n", arg);
}
void
func2(long arg)
{
printf("func2: arg = %ld\n", arg);
}
sopwith gcc -O2 -Wconversion conversion2.c -o conversion2
conversion2.c: In function `main':
conversion2.c:12: warning: passing arg 1 of `func2' with different width due to
prototype
conversion2.c:15: warning: passing arg 1 of `func1' with different width due to
prototype
conversion2.c:19: warning: passing arg 1 of `func1' with different width due to
prototype
sopwith ./conversion2
func1: arg = 5
func2: arg = 5
func1: arg = 5
func2: arg = 5
func1: arg = -1539607552
func2: arg = 50000000000
sopwith
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=9072
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