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From: David Levine <levinedl AT acm DOT org>
Subject: Re: nested popen()'s lead to fgets() failure on 64-bit only
In-Reply-To: Your message of Mon, 13 Jan 2014 13:09:33 +0100
Date: Mon, 13 Jan 2014 09:35:35 -0500
Message-ID: <25675-1389623735.405019@VSdY.Cv9S.eTM_>

Corinna wrote:

> That's the version number of the setup-x86_64.exe tool, not the version
> number of Cygwin.  Try `uname -r'.

1.7.27(0.271/5/3)

> Maybe you're calling the wrong file command?  What's your $PATH set to?
> What if you change your popen call to run /usr/bin/file.exe with full
> path?
> 
>   if ((f2 = popen("/usr/bin/file --mime-type /usr/bin/file.exe", "r")))

My PATH picks /usr/bin/file, but just to be sure I hard coded it,
and also used it for the first popen(), and also set PATH to /usr/bin:

$ gcc -o nested_popen nested_popen.c -Wall -Wextra && \
  PATH=/usr/bin ./nested_popen
  buf1 = /usr/bin/file.exe: application/x-dosexec
popen: No error
fgets2 EOF

It shouldn't be at EOF in this case.  If I change the
second popen() to open anything, e.g.,
popen("garbage,really", "r"), it still reports success.
We're getting closer?

David


#include <stdio.h>

int
main() {
  FILE *f1, *f2;

  if ((f1 = popen("file --mime-type /usr/bin/file.exe", "r"))) {
    char buf1[BUFSIZ];

    while (fgets(buf1, sizeof buf1, f1)) {
      printf("  buf1 = %s", buf1);

      if ((f2 = popen("/usr/bin/file.exe --mime-type /usr/bin/file.exe",
                      "r"))) {
        char buf2[BUFSIZ];

        perror("popen");

        /* This fgets call fails on 64-bit Cygwin 1,7.27(0.271/5/3),
           with "No error". */
        if (fgets(buf2, sizeof buf2, f2)) {
          printf("  buf2 = %s", buf2);
        } else if (feof (f2)) {
          fputs ("fgets2 EOF\n", stderr);
        } else {
          perror("fgets2");
        }

        pclose(f2);
      } else {
        perror("popen2");
      }
    }

    pclose(f1);
  } else {
    perror("popen1");
  }

  return 0;
}

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