[Mingw-notify] [ mingw-Bugs-944512 ] ostringstream + threads

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Bugs item #944512, was opened at 2004-04-30 02:31
Message generated for change (Comment added) made by dannysmith
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Category: gcc
Group: None
Status: Open
Resolution: Accepted
Priority: 5
Submitted By: Christoph Wiedemann (wiedeman)
Assigned to: Danny Smith (dannysmith)
Summary: ostringstream + threads

Initial Comment:
Hi,

std::ostringstream doesn't seem to be reentrant. I have a minimal test case:

// myexe.cpp
#include <iostream>
#include <sstream>

using namespace std;

#include <windows.h>
#include <winbase.h>

void run() {
  int k = 0;
  while(1) {
    ostringstream s;
    s << k++;
    k %= 10;
  }
}

int main(int argc, char **argv) {
  DWORD id1, id2;
  CreateThread(0, 0, (LPTHREAD_START_ROUTINE)&run, 0, 0, &id1);
  run();
  return 0;
}
// end myexe.cpp

Compiling with

g++ -g -mthreads -c -o myexe.o myexe.cpp
g++ -mthreads -mconsole -o myexe.exe myexe.o

and executing myexe.exe results in an Access Violation with the (broken) call stack:

Call stack:
78002827  msvcrt.dll:78002827  strcat

Windows 2000 (SP 2)
Mingw installer is MinGW-3.1.0-1.exe

gcc -v:
Reading specs from C:/MinGW/Bin/../lib/gcc-lib/mingw32/3.2.3/specs
Configured with: ../gcc/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls --enable-languages=c++,f77,o
bjc --disable-win32-registry --disable-shared --enable-sjlj-exceptions
Thread model: win32
gcc version 3.2.3 (mingw special 20030504-1)

ld -v:
GNU ld version 2.13.90 20030111

Thank you,
Christoph


----------------------------------------------------------------------

>Comment By: Danny Smith (dannysmith)
Date: 2005-02-16 08:48

Message:
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I didn't meqn the snippet I sent to be interpreted as a 
workaround, rather as a reduced testcase that also fails 
(even without stringstreams)


I think the only quick solution is to use your own float-to-
string conversion.  If your desparate I can provide a newer 
libstdc++.a that should work with G++-3.4.2 that has the fix.
The float conversion is also much faster with the newer lib.

Danny

----------------------------------------------------------------------

Comment By: John D. Lomonaco (jdlomonaco)
Date: 2005-02-16 02:52

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Danny,

Again, thank you for the quick come back as we are on a 
fairly tight schedule. 

I'm not sure, however, how to apply the changes in the 
modified minimal program you included into our use of the  
ostringstream when appending a float. Would it be as shown 
in the following code segment?

   #include <windows.h>
   #include <winbase.h>
   #include <string.h>
   #include <malloc.h>
   #include <locale.h>
    .
    .
   void function (void)
   {
       ostringstream osTemp;
        .
        .
       char* __old = setlocale(LC_ALL, NULL);
       char* __sav = (char*) malloc(strlen(__old) + 1);
       strcpy(__sav, __old);
       setlocale(LC_ALL, "C");

       osTemp << 1.0f; // A function actually supplies the float.

       setlocale(LC_ALL, __sav);
       free (__sav);
        .
        .
    }

Will this fix the problem even with GCC version 3.2.3?

This change will require a good deal of edititing everywhere 
we use ostringstream even if we use macros or an object 
(and we use this a lot). So I have to ask, how firm is the date 
on version 3.4.4? 

Thanks,

John

----------------------------------------------------------------------

Comment By: Danny Smith (dannysmith)
Date: 2005-02-15 09:51

Message:
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Hi, the problem you report actually is a CRT problem with 
setlocale.

libstdc++'s conversion of float to string calls setlocale to 
make sure that LC_NUMERIC is set to "C", then resets it to old 
value

The repeated calls to setlocale by the conversion in your loop 
eventually break the locking/unlocking of thread-local locale 
data 

Try 

#include <windows.h>
#include <winbase.h>
#include <string.h>
#include <malloc.h>
#include <locale.h>
void run() {
  while(1) {
    char* __old = setlocale(LC_ALL, NULL);
    char* __sav = (char*) malloc(strlen(__old) + 1);
    strcpy(__sav, __old);
    setlocale(LC_ALL, "C");
   //  snprintf a number
    setlocale(LC_ALL, __sav);
    free (__sav);
  }
}


int main(int argc, char **argv) {
  DWORD id1, id2;

  CreateThread(0, 0, (LPTHREAD_START_ROUTINE)&run, 0, 0, 
&id1);
  run();
  return 0;
}


The bug is avoided by very recent patch to libstc++, so will 
not cause probelm with release of gcc 3.4.4 ( another month 
or so)

Danny.  

----------------------------------------------------------------------

Comment By: John D. Lomonaco (jdlomonaco)
Date: 2005-02-15 03:12

Message:
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OOPs, (I somehow submitted my append prior to finishing)

The complete code segment shown below even works with 
GCC version 3.2.3 but its a little messy with respect to 
setting percission of the float in the stream. I included 
formating for the percission I desired.

    ostringstream osTemp;
    .
    .
    char buff[6];
    sprintf (buff, "%4.2f", 1.0f);
    osTemp << buff; 
    .
    .


John


----------------------------------------------------------------------

Comment By: John D. Lomonaco (jdlomonaco)
Date: 2005-02-15 03:05

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Danny,

Thanks for the confirmation. I looked at the down loads and 
could not find a GCC version 4.0.0. When will it be available?
We are on a schedule with my current project. 

By the way I have verified a "work around" by using sprintf to 
convert and buffer a float into a char * then concatinating 
this to the ostringstream. 

char buff[6];
    sprintf (buff, "%4.2f", 1.0f);
    osTemp << buff; 

----------------------------------------------------------------------

Comment By: Danny Smith (dannysmith)
Date: 2005-02-12 11:34

Message:
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I can confiorm jdlomonaco's  report that it is still broken, 
using double in modified testcase, with gcc 3.4.2 and 3.4.4.

GCC 4.0.0 works but it uses a different allocator.

Danny

----------------------------------------------------------------------

Comment By: John D. Lomonaco (jdlomonaco)
Date: 2005-02-12 08:45

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I am looking at this problem with interest. It's status is 
closed. However, We are currently experiencing the same 
problem with ostringstream with float concatinations to the 
stream.  I also tried concatinating int and it failed also but 
char did not. We currently compile with version 3.2.3 for our 
builds. However, we loaded the 3.4.2 version of the compiler 
on one of our PCs and compiled with it.  Floats still fail with 
the same error.   Our test system runs Windows XP. Any help 
will be appreciated. 

----------------------------------------------------------------------

Comment By: Danny Smith (dannysmith)
Date: 2004-04-30 19:29

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I don't have gcc-3.2.3 anymore, but on 3.3.3 and 3.4.0 and 
gcc trunk your testcase runs without problem, so I'll close 
this bug as fixed.

Danny

----------------------------------------------------------------------

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