printf long double in cygwin GCC

Asked Sep 29 '17 at 03:07

Active Sep 29 '17 at 04:59

Viewed 157 times

I am trying to printf a long double value in C, but it doesn't give the correct value. I have tried using different format parameters, but I'm not sure what to make of the output. I read from some other answers that it might be a problem with the compiler/OS, but I haven't managed to solve the problem.

I use cygwin GCC compiler on windows 7.

#include <stdio.h>
long double ans;

int main(){
    ans = 1.2457473567352;
    printf("long double ans = %.20Lf \n",ans);
}

The output:

long double ans = 0.000000000000000
long double ans = 1.133046674395481e-317

asked Sep 29 '17 at 03:07

Joel Wong

1

I tried it and it displays the good value. Your processor is 32 or 64 bits? – YaatSuka Sep 29 '17 at 03:21
My cygwin is 64 bits, as well as windows – Joel Wong Sep 29 '17 at 03:25
https://www.computerhope.com/issues/ch001121.htm – YaatSuka Sep 29 '17 at 03:26
My cygwin is 64 bits, as well as windows – Joel Wong Sep 29 '17 at 03:26
Ok, because I know one similar case and the problem was the 32-bits processor. But now, I don't know if the problem come from Cygwin, but your code sounds good! – YaatSuka Sep 29 '17 at 03:30
Code has 1 `printf()` call. Out has 2 lines. Please clarify, were 2 lines printed? – chux - Reinstate Monica Sep 29 '17 at 03:42
1

i also think the problem is with gcc ... this https://stackoverflow.com/questions/26296058/cant-print-correctly-a-long-double-in-c may help you – IR Emon Sep 29 '17 at 03:45
Are you linking in the math library? Try adding some FP math in `main()` – chux - Reinstate Monica Sep 29 '17 at 03:45
https://stackoverflow.com/questions/4089174/printf-and-long-double – Artemy Vysotsky Sep 29 '17 at 04:37
Check the answer with the bounty in Artemy link. – Yunnosch Sep 29 '17 at 05:04
as mentioned by @chux the printf code does not match with the output you show. It seems your are mixing different test codes. It works fine for me with cygwin gcc 6.4.0 `$ ./a long double ans = 1.24574735673519998436` – matzeri Sep 29 '17 at 06:18

printf long double in cygwin GCC

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