Bug#576485: Acknowledgement (libstdc++: std::thread completely broken)

[Miles Bader <miles@gnu.org>]

BTW, one thing I noticed is that the "error code" field in the
std::system_error exception which is raised, seems to be set to EPERM
("Operation not permitted"), but this code is not apparently caused by a
system call (determined by stracing the process).

For instance, changing the test case to this:

  #include <cerrno>
  #include <iostream>
  #include <thread>

  int g = 0;

  void f ()
  {
    g++;
  }

  int main ()
  {
    std::cerr << "before thread creation..." << std::endl;
    try {
      errno = 0;
      std::thread t (f);
      std::cerr << "after thread creation..." << std::endl;
      t.join ();
    } catch (const std::system_error &e) {
      std::cerr << "caught std::system_error, what = \""
		<< e.what ()
		<< "\", code = " << e.code().message ()
		<< std::endl;
    }
    std::cout << "after joing, g = " << g << std::endl;
    return 0;
  }

Results in this:

   $ g++-4.5 -std=c++0x -o t t.cc
   $ ./t
   before thread creation...
   caught std::system_error, what = "", code = Operation not permitted
   after joing, g = 0

strace shows this:

   $ strace ./t 2>&1 | tail -20
   mprotect(0x7f2036a9c000, 16384, PROT_READ) = 0
   mprotect(0x7f2036f3c000, 4096, PROT_READ) = 0
   mprotect(0x7f2037229000, 32768, PROT_READ) = 0
   mprotect(0x7f2037464000, 4096, PROT_READ) = 0
   munmap(0x7f203744b000, 90011)           = 0
   write(2, "before thread creation...", 25before thread creation...) = 25
   write(2, "\n", 1
   )                       = 1
   brk(0)                                  = 0x18b2000
   brk(0x18d3000)                          = 0x18d3000
   write(2, "caught std::system_error, what ="..., 34caught std::system_error, what = ") = 34
   write(2, "\", code = ", 10", code = )             = 10
   write(2, "Operation not permitted", 23Operation not permitted) = 23
   write(2, "\n", 1
   )                       = 1
   fstat(1, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
   mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2037460000
   write(1, "after joing, g = 0\n", 19after joing, g = 0
   )    = 19
   exit_group(0)                           = ?


Thanks,

-Miles

-- 
Cabbage, n. A familiar kitchen-garden vegetable about as large and wise as a
man's head.