g++ 4.7.2 error: 'mutex' in namespace 'std' does not name a type

[Elkvis]

I've verified this on ubuntu 12.10 and on windows/mingw, and found that g++ version 4.7.2 seems to have broken thread/mutex support. has anyone else observed this?

[Salem]

Can you post your test case?

[phantomotap]

has anyone else observed this?

I usually build my own package for "Windows", so maybe it is just my builds script, but that seems par for the course under "MinGW".

I can't speak to anything about "Ubuntu".

My understanding, and only that, is that a lot of work needs to be done for "libstdc++" before the implementation has the proper safety the respect to the standard. You may not, and probably will not, be able to match your own expectations with "libstdc++" for a bit longer.

Soma

[Elkvis]

Can you post your test case?

this was my actual test case

#include <iostream>
#include <thread>
#include <vector>
#include <memory>

std::mutex mutex;
int mutexProtected = 0;

void threadProc()
{
    for (int i = 0; i < 5; ++i)
    {
	std::lock_guard<std::mutex> lock(mutex);
	std::cout << "Value: " << ++mutexProtected << std::endl;
    }
}

int main()
{
    std::vector<std::shared_ptr<std::thread> > threadVector;

    for (int i = 0; i < 20; ++i)
    {
	threadVector.push_back(std::shared_ptr<std::thread>(new std::thread(threadProc)));
    }

    for (auto& thread : threadVector)
    {
	thread->join();
    }

    return 0;
}

my compile command is

g++ -pthread -std=c++0x -c main.cpp

and the output I get on mingw is

main.cpp:6:1: error: 'mutex' in namespace 'std' does not name a type
main.cpp: In function 'void threadProc()':
main.cpp:13:2: error: 'lock_guard' is not a member of 'std'
main.cpp:13:18: error: 'mutex' is not a member of 'std'
main.cpp:13:35: error: 'mutex' was not declared in this scope
main.cpp:13:40: error: 'lock' was not declared in this scope
main.cpp: In function 'int main()':
main.cpp:22:33: error: 'thread' is not a member of 'std'
main.cpp:22:33: error: 'thread' is not a member of 'std'
main.cpp:22:44: error: template argument 1 is invalid
main.cpp:22:46: error: template argument 1 is invalid
main.cpp:22:46: error: template argument 2 is invalid
main.cpp:22:60: error: invalid type in declaration before ';' token
main.cpp:26:15: error: request for member 'push_back' in 'threadVector', which is of non-class type 'int'
main.cpp:26:41: error: 'thread' is not a member of 'std'
main.cpp:26:41: error: 'thread' is not a member of 'std'
main.cpp:26:52: error: template argument 1 is invalid
main.cpp:26:58: error: expected type-specifier
main.cpp:26:58: error: expected ')'
main.cpp:29:25: error: no matching function for call to 'begin(int&)'
more errors snipped...

even a simple test case like this exhibits essentially the same behavior

#include <mutex>

int main()
{
    std::mutex mutex;
    return 0;
}

there were many more errors, but they were all related to the compiler's inability to find a begin() or end() function for std::vector<std::shared_ptr<std::thread> >.

after more digging, I determined that on ubuntu, modifying the code to include <mutex> solved the problem. it seems that <mutex> was included implicitly by <thread> in g++ 4.6.3 on fedora 15, and a recent move to ubuntu 12.10 (gcc 4.7.3) for my main dev machine exposed that fact.

on mingw (gcc 4.7.3), including <mutex> did not solve the problem. it appears that the std::thread implementation in the official release of mingw version of g++ 4.7.3 is incomplete or nonexistent.

[jimblumberg]

You may want to include <mutex> to use the mutex class. After I add that include file your program compiles without errors for me. But I do use the -std=c++11 flag instead of -std=c++0x.

Jim

[Elkvis]

You may want to include <mutex> to use the mutex class. After I add that include file your program compiles without errors for me.

as I said in my last post, that fixes it on ubuntu, but not on windows.

But I do use the -std=c++11 flag instead of -std=c++0x.

changing -std=c++0x to -std=c++11 makes no difference. my guess is that they are equivalent.

[jimblumberg]

changing -std=c++0x to -std=c++11 makes no difference. my guess is that they are equivalent.

Not on my system. If I change to -std=c++0x I get these errors:

/usr/include/c++/4.7/bits/c++0x_warning.h|32|error: #error This file requires compiler and library support for the ISO C++ 2011 standard. This support is currently experimental, and must be enabled with the -std=c++11 or -std=gnu++11 compiler options.|
main.cpp||In function ‘int main()’:|
main.cpp|5|error: ‘mutex’ is not a member of ‘std’|
main.cpp|5|error: expected ‘;’ before ‘mutex’|
||=== Build finished: 3 errors, 0 warnings ===|

Jim

[Elkvis]

changing -std=c++0x to -std=c++11 makes no difference. my guess is that they are equivalent.

Not on my system. If I change to -std=c++0x I get these errors:



Jim

what actual version of gcc is it? (gcc --version)

[jimblumberg]

Version 4.7.2

Jim

[Elkvis]

that's interesting. both produce identical results on my ubuntu and mingw systems with 4.7.3.

[stahta01]

In my Code::Blocks with MinGW GCC (gcc version 4.7.1 (tdm-1)),
_GLIBCXX_HAS_GTHREADS is not defined.

From mutex header.

#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)

namespace std _GLIBCXX_VISIBILITY(default)
{

I am guessing that there is a option that compiles MinGW GCC with this _GLIBCXX_HAS_GTHREADS defined.

Tim S.

[kmdv]

MinGW-w64 does support C++11 threads, and despite its name, it is also for 32-bit (which I personally use):
GCC for both x64 & x86 Windows! - MinGW-w64