[Mingw-notify] [ mingw-Bugs-2843440 ] operator>>(istream, double) not thread safe (g++)

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Bugs item #2843440, was opened at 2009-08-24 11:18
Message generated for change (Tracker Item Submitted) made by bronf
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Category: gcc
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Frédéric Bron (bronf)
Assigned to: Nobody/Anonymous (nobody)
Summary: operator>>(istream, double) not thread safe (g++)

Initial Comment:
operator>>(istream, double) is not thread safe.
The following small program demonstrates the issue (proved on mingw32-g++ 3.4.4, 3.4.5 and 4.4.0):

$ g++ -mthreads -o thread_bug thread_bug.cc
$ .\thread_bug.exe

This will lead to one of the following error messages:
- The instruction at "0x77c3330c" referenced memory at "0x00000000". The memory could not be "read."
- The instruction at "0x77c33509" referenced memory at "0x00000000". The memory could not be "read."

#include <windows.h>
#include <iostream>
#include <sstream>

DWORD WINAPI task(LPVOID lpArg) {
        double x ;
        for (int k=0 ; k<10000 ; ++k) {
                std::istringstream is("10") ;
                is >> x ;
        }
        std::cout << "task ended: " << x << std::endl ;
        return 0 ;
}

int main() {
        const int N=10 ;
        HANDLE hHandles[N] ;
        for (int k=0 ; k<N ; ++k) {
                hHandles[k]=CreateThread(NULL, 0, task, NULL, 0, NULL) ;
        }
        for (int k=0 ; k<N ; ++k) WaitForSingleObject(hHandles[k], INFINITE) ;
        return 0 ;
}


* The same program works fine with:
- MSVC++ 2008,
- g++ 4.3.2 on linux 64 (using pthreads),
- intel compiler 10.0 on linux 64 (using pthreads).
* There is no bug reading an "int". Reading double leads to an issue.
* mingw32-g++ links to msvcrt.dll where msvc++ 2008 links to msvcp90.dll and msvcr90.dll.
* Same bug reading from a file.
* No bug with pure C code reading from a file with fscanf.


The bug appears in these conditions:

* platform:
Windows XP SP3,

* gcc version:

Using built-in specs.
Target: mingw32
Configured with: ../gcc-4.4.0/configure --enable-languages=c,ada,c++,fortran,java,objc,obj-c++ --disable-sjlj-exceptions --enable-shared --enable-libgcj --enable-libgomp --with-dwarf2 --disable-win32-registry --enable-libstdcxx-debug --enable-version-specific-runtime-libs --prefix=/mingw --with-gmp=/mingw/src/gmp/root --with-mpfr=/mingw/src/mpfr/root --build=mingw32
Thread model: win32
gcc version 4.4.0 (GCC) 

* binutils:
GNU ld (GNU Binutils) 2.19.1

* build Environment
Microsoft Shell (%SystemRoot%\system32\cmd.exe)

The bug also appears using the cygwin platform and g++ 3.4.4 with -mno-cygwin flag.

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