musl compatibility

[v01dXYZ]

musl has some discrepancies with glibc that causes some issues at compilation/run:

• headers that don't provide the same set of symbols (time.h)
• usage of routines that depends on behaviour left to the implementation by the spec (random). At the end, the program generates very different outputs.

Feel free to suggest the right tags for the commits ([MultiSource], [CLAMR], ...).

[v01dXYZ]

I found a discrepancy related to the way buffered IO is implemented by libc.

#include <stdio.h>
#include <unistd.h>

#define WRITE(fd, str) \
  do { \
  char s[] = str;                               \
  write(fd, s, sizeof(s)); \
  } while (0)

int main(int argc, char **argv)
{
  if(argc < 2) {
    fprintf(stdout, "stdout\n");
    fprintf(stderr, "stderr\n");
  } else {
    WRITE(STDOUT_FILENO, "stdout\n");
    WRITE(STDERR_FILENO, "stderr\n");
  }

  return 0;
}

When you use the following command line, with glibc we have

$ ./buff_io_discrepancy 2>&1 | cat # no argument  -> buffered IO
stderr
stdout
$ ./buff_io_discrepancy direct 2>&1 | cat # argument -> direct IO
stdout
stderr

musl always outputs the same (in this very case at least, I don't know if it holds always true).

This problem appears too with a >out 2>&1.
I don't know how to solves this problem, except by considering using separate reference files for stdout/stderr.