Bug 191758

Version:            (using Devel)
OS:                Linux
Installed from:    Compiled sources

Valgrinding chromium on both Mac and Linux, we saw errors of the sort

==74890== Warning: invalid file descriptor 256 in syscall close()

(see http://crbug.com/11412).  Turns out we were looping over all
open file descriptors, as reported by the system, and some of
those were valgrind's!  Here's a little test program demonstrating
the issue.  It would be sweet if valgrinding this test program
did not produce any warnings about invalid fds.  Valgrind could
presumably hide them from being visible via /proc/self/fd or /dev/fd
with a little effort.  We've now worked around this in our app
by ignoring any fds above the system limit for our process.

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/resource.h>
#include <sys/types.h>
#include <unistd.h>

#include <limits>
#include <iostream>
#include <set>

int main(int argc, char **argv)
{
#if defined(linux)
  static const rlim_t kSystemDefaultMaxFds = 8192;
  static const char fd_dir[] = "/proc/self/fd";
#elif defined(__APPLE__ & __MACH__)
  static const rlim_t kSystemDefaultMaxFds = 256;
  static const char fd_dir[] = "/dev/fd";
#endif
  std::set<int> saved_fds;

  // Get the maximum number of FDs possible.
  struct rlimit nofile;
  rlim_t max_fds;
  if (getrlimit(RLIMIT_NOFILE, &nofile)) {
    // getrlimit failed. Take a best guess.
    max_fds = kSystemDefaultMaxFds;
    std::cerr << "getrlimit(RLIMIT_NOFILE) failed: " << errno;
  } else {
    max_fds = nofile.rlim_cur;
  }
  std::cout << "max_fds is " << max_fds << "\n";

  if (max_fds > INT_MAX)
    max_fds = INT_MAX;

  // Don't close stdin, stdout and stderr
  saved_fds.insert(STDIN_FILENO);
  saved_fds.insert(STDOUT_FILENO);
  saved_fds.insert(STDERR_FILENO);

  
  DIR *dir = opendir(fd_dir);
  if (NULL == dir) {
    std::cerr << "Unable to open " << fd_dir;
    exit(1);
  }

  struct dirent *ent;
  while ((ent = readdir(dir))) {
    // Skip . and .. entries.
    if (ent->d_name[0] == '.')
      continue;

    char *endptr;
    errno = 0;
    const long int fd = strtol(ent->d_name, &endptr, 10);
    if (ent->d_name[0] == 0 || *endptr || fd < 0 || errno)
      continue;

    // When running under Valgrind, Valgrind opens several FDs for its
    // own use and will complain if we try to close them.  All of
    // these FDs are >= |max_fds|, so we can check against that here
    // before closing.
    if (fd >= static_cast<int>(max_fds))
      std::cout << "Found fd " << fd << " outside the normal range -- is it valgrind's?\n";
    // don't check - let valgrind warn
    close(fd);
  }
}