On Mon, Nov 30, 2015 at 11:09 PM, Nicolas George <geo...@nsup.org> wrote:
> Le decadi 10 frimaire, an CCXXIV, Muhammad Faiz a écrit :
>> double basefreq = BASEFREQ, endfreq = ENDFREQ;
>> if (basefreq == BASEFREQ && endfreq == ENDFREQ)
>> printf("equal\n");
>> else
>> printf("inequal\n");
>>
>> I try with gcc -std=c89 / -std=c99 on mingw 32-bit
>> the result is inequal.
>
> That looks like a compiler bug. Could you post the generated assembly code,
> with and without the cast? (and with just one comparison, no need to make
> things complicated)
#include <stdio.h>
#define BASEFREQ 20.01523126408007475
double basefreq = BASEFREQ;
int
main(int argc, char** argv)
{
if (basefreq == BASEFREQ)
printf("equal\n");
else printf("inequal\n");
return 0;
}
gcc -c -std=c89 -O2
without cast:
00000000 <_main>:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 83 e4 f0 and $0xfffffff0,%esp
6: 83 ec 10 sub $0x10,%esp
9: e8 00 00 00 00 call e <_main+0xe>
e: dd 05 00 00 00 00 fldl 0x0
14: db 2d 10 00 00 00 fldt 0x10
1a: d9 c9 fxch %st(1)
1c: df e9 fucomip %st(1),%st
1e: dd d8 fstp %st(0)
20: 7a 02 jp 24 <_main+0x24>
22: 74 10 je 34 <_main+0x34>
24: c7 04 24 06 00 00 00 movl $0x6,(%esp)
2b: e8 00 00 00 00 call 30 <_main+0x30>
30: 31 c0 xor %eax,%eax
32: c9 leave
33: c3 ret
34: c7 04 24 00 00 00 00 movl $0x0,(%esp)
3b: e8 00 00 00 00 call 40 <_main+0x40>
40: eb ee jmp 30 <_main+0x30>
with cast:
00000000 <_main>:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 83 e4 f0 and $0xfffffff0,%esp
6: 83 ec 10 sub $0x10,%esp
9: e8 00 00 00 00 call e <_main+0xe>
e: dd 05 00 00 00 00 fldl 0x0
14: dd 05 10 00 00 00 fldl 0x10
1a: d9 c9 fxch %st(1)
1c: df e9 fucomip %st(1),%st
1e: dd d8 fstp %st(0)
20: 7a 02 jp 24 <_main+0x24>
22: 74 10 je 34 <_main+0x34>
24: c7 04 24 06 00 00 00 movl $0x6,(%esp)
2b: e8 00 00 00 00 call 30 <_main+0x30>
30: 31 c0 xor %eax,%eax
32: c9 leave
33: c3 ret
34: c7 04 24 00 00 00 00 movl $0x0,(%esp)
3b: e8 00 00 00 00 call 40 <_main+0x40>
40: eb ee jmp 30 <_main+0x30>
without cast with -std=gnu89:
00000000 <_main>:
0: 55 push %ebp
1: 89 e5 mov %esp,%ebp
3: 83 e4 f0 and $0xfffffff0,%esp
6: 83 ec 10 sub $0x10,%esp
9: e8 00 00 00 00 call e <_main+0xe>
e: dd 05 00 00 00 00 fldl 0x0
14: dd 05 10 00 00 00 fldl 0x10
1a: d9 c9 fxch %st(1)
1c: df e9 fucomip %st(1),%st
1e: dd d8 fstp %st(0)
20: 7a 02 jp 24 <_main+0x24>
22: 74 10 je 34 <_main+0x34>
24: c7 04 24 06 00 00 00 movl $0x6,(%esp)
2b: e8 00 00 00 00 call 30 <_main+0x30>
30: 31 c0 xor %eax,%eax
32: c9 leave
33: c3 ret
34: c7 04 24 00 00 00 00 movl $0x0,(%esp)
3b: e8 00 00 00 00 call 40 <_main+0x40>
40: eb ee jmp 30 <_main+0x30>
without cast and use -std=c89, gcc uses fldt instead of fldl
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