time command does not show CPU time for MinGW binaries

daniel@poradnik-webmastera.com daniel@poradnik-webmastera.com
Sun Jan 7 16:02:00 GMT 2018


time command does not show CPU time for MinGW binaries. I have this 
sample piece of code:

#include <stdio.h>
#include <time.h>

#define N 100000
#define K 10000

double data[N];

int main()
{
     clock_t t = clock();
     for (unsigned long n = 0; n < N; ++n)
         for (unsigned long k = 0; k < K; ++k)
             data[n] += data[n] * data[k];

     t = clock() - t;
     printf("Time %.3f\n", (double)t / CLOCKS_PER_SEC);

     return 0;
}

When I compile it using Cygwin's gcc, time shows CPU time (user time) as 
expected:

$ gcc -o test test.c -O3
$ time ./test
Time 1.890

real    0m2,043s
user    0m1,890s
sys     0m0,000s

However when code is compiled using MinGW's gcc, time reports 0.000 as a 
user time. Note that clock() function still provides valid values:

$ x86_64-w64-mingw32-gcc -o test test.c -O3
$ time ./test
Time 1.889

real    0m1,998s
user    0m0,000s
sys     0m0,015s

I have updated Cygwin to latest version today.
$ uname -r
2.9.0(0.318/5/3)

gcc (GCC) 6.4.0
x86_64-w64-mingw32-gcc (GCC) 6.4.0

I am using Win10 Pro now. As I recall, it worked when I was using it 
about year ago on Win7 Pro. So it is probably Win10 issue.

Is this a known bug, or should I log a new one? Do you know if there is 
any workaround?

Daniel

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