tcc does not follow the integer promotion rules on bit-fields.
For instance, consider the following code:
#include <stdio.h>
union ui
{
struct
{
unsigned int manl:32;
unsigned int manh:20;
unsigned int exp:11;
unsigned int sig:1;
} s;
double d;
};
union ul
{
struct
{
unsigned long manl:32;
unsigned long manh:20;
unsigned long exp:11;
unsigned long sig:1;
} s;
double d;
};
int main (void)
{
union ui xi;
union ul xl;
xi.d = 0.5;
xl.d = 0.5;
printf ("%d %lx\n", xi.s.exp - 1023 < 0, (unsigned long) (xi.s.exp - 1023));
printf ("%d %lx\n", xl.s.exp - 1023 < 0, (unsigned long) (xl.s.exp - 1023));
return 0;
}
With GCC and ICC, I get:
1 ffffffffffffffff
1 ffffffffffffffff
But with tcc, I get:
0 ffffffff
0 ffffffffffffffff
Since all the values of xi.s.exp and xl.s.exp are representable
in an int, the bit-field type should be converted to int for the
subtraction, so that the < 0 should be true in both cases.
--
Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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