Bugs item #2843440, was opened at 2009-08-24 04:18
Message generated for change (Comment added) made by jimmbelll
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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.
----------------------------------------------------------------------
Comment By: Jim Bell (jimmbelll)
Date: 2011-03-06 15:34
Message:
I'm seeing this exact behavior using the latest MinGW release (20110211,
g++ 4.5.2) on Windows XP (automatic updates enabled), msvcrt.dll
7.0.2600.5512.
Work-around: If you serialize access to every istream (istringstream,
istrstream, ifstream), locking the mutex from before its created until
after it's destructed, then multi-threaded access works. Anything less
crashes the app.
----------------------------------------------------------------------
Comment By: Frédéric Bron (bronf)
Date: 2009-09-22 02:03
Message:
I tested the program compiled on XP and runned on Vista with version
7.0.6002.18005 of msvcrt.dll: no issue.
Does this mean it is a Windows bug and mingw has nothing to do with it? Is
there any workaround for machine using older version of msvcrt.dll?
----------------------------------------------------------------------
Comment By: Danny Smith (dannysmith)
Date: 2009-08-26 02:51
Message:
I cannot reproduce the error with gcc 4.5.0 on my Vista laptop. I will try
older versions of gcc when I get home.
Danny
----------------------------------------------------------------------
Comment By: Frédéric Bron (bronf)
Date: 2009-08-26 02:17
Message:
My msvcrt.dll version is 7.0.2600.5512.
Do you reproduce the bug on your Vista?
----------------------------------------------------------------------
Comment By: Danny Smith (dannysmith)
Date: 2009-08-25 22:01
Message:
What is the version number of your msvcrt.dll (look at the file properties
to get the version from the versioninfo resource.)
Older msvcrt.dll's (eg 6.10.8924.0) had thread-locking problems with
setlocale that causes a similar bug in libstdc++. The msvcrt.dll that
ships with Vista (mine has version number 7.0.6001.18000) works fine.
----------------------------------------------------------------------
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