The disagreement of glibc and mingw-w64 (in my opinion) is definitely glibc's
bug:
lh_mouse@lhmouse-dev:~$ cat test3.c
#include <stdio.h>
#include <math.h>
int main(){
double x = 10.001000;
double y = 0.701000;
int quo;
double rem = remquo(x, y, &quo);
printf("%f %f %d %f\n", x, y, quo, rem);
}
lh_mouse@lhmouse-dev:~$ gcc test3.c -lm -O0 && ./a.out # use glibc
10.001000 0.701000 8 4.393000
lh_mouse@lhmouse-dev:~$ gcc test3.c -lm -O2 && ./a.out # performs constant
folding
10.001000 0.701000 14 0.187000
lh_mouse@lhmouse-dev:~$
The remainder of `remquo` from mingw-w64 seems all right.
However the value (or rather, the 3 least significant bits) returned in the
third parameter
still seems problematic.
------------------
Best regards,
lh_mouse
2016-09-06
-------------------------------------------------------------
发件人："lhmouse"<lh_mo...@126.com>
发送日期：2016-09-05 23:08
收件人：mingw-w64-public,lhmouse
抄送：
主题：Re: [Mingw-w64-public] Wrong quotient results of `remquo()`?
Found an example on cppreference:
http://en.cppreference.com/w/cpp/numeric/math/remquo
The example shows that, since `cos()` is periodic,
adding 1000000000000 * PI to its parameter doesn't change the result.
But, we can also say that, subtracting 1000000000000 * PI
from its parameter should not change the result either. However,
with mingw-w64 and MSVCRT, it DOES change the result,
as shown on the last line:
E:\Desktop>g++ test.cpp -std=c++14
E:\Desktop>a.exe
cos(pi * -0.25) = 0.707107
cos(pi * -1.25) = -0.707107
cos(pi * -1000000000000.25) = 0.707123
cos(pi * -1000000000001.25) = -0.707117
cos(pi * -1000000000000.25) = 0.707107
cos(pi * -1000000000001.25) = 0.707107
This could be a potential bug.
------------------
Best regards,
lh_mouse
2016-09-05
-------------------------------------------------------------
发件人："lhmouse"<lh_mo...@126.com>
发送日期：2016-09-05 22:27
收件人：mingw-w64-public
抄送：
主题：[Mingw-w64-public] Wrong quotient results of `remquo()`?
Hello guys,
I am testing my `remquo()` implementation when I find that `remquo`
on Linux (using glibc) and on Windows (using mingw-w64) generate
different results. I don't think this is the correct behavior. Any ideas?
The testcases in file `remquo.txt` the attached zip file was generated
on my VPS running Debian. MinGW-w64 is failing some of them:
E:\Desktop\remquo_test>gcc test.c -std=c99 && a.exe > nul
passed: 37864
failed: 2537
--------------
Best regards,
lh_mouse
2016-09-05
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