On 03/14/14 19:49, Laszlo Ersek wrote:
> One good example is for 6.4.4.1 "Integer constants":
>
> QUIET CHANGE IN C99
>
> Unsuffixed integer constants may have different types in C99 than
> in C89. Such constants greater than LONG_MAX are of type unsigned
> long in C89, but are of type long long in C99 (if long long has
> more range than long).
>
> I have no clue what gnu89 does.
x.c:
#include <stdio.h>
int
main(void)
{
fprintf(stdout, "%u\n", (unsigned)sizeof 2147483648);
return 0;
}
The following script:
for I in c89 gnu89 c99 gnu99; do
echo "==== $I ===="
gcc -m32 -o x -std=$I x.c
./x
done
outputs:
==== c89 ====
x.c: In function 'main':
x.c:6:3: warning: this decimal constant is unsigned only in ISO C90
[enabled by default]
fprintf(stdout, "%u\n", (unsigned)sizeof 2147483648);
^
4
==== gnu89 ====
x.c: In function 'main':
x.c:6:3: warning: this decimal constant is unsigned only in ISO C90
[enabled by default]
fprintf(stdout, "%u\n", (unsigned)sizeof 2147483648);
^
4
==== c99 ====
8
==== gnu99 ====
8
Laszlo
