Posts

Strange behaviour of std::thread in Visual Studio 2012

Today I came across some strange behaviour with the VS2012 implementation of std::thread. The created thread’s job was to access the XIMEA camera API, one method of thread creation worked ok, and another only half worked.

With the first mode the API could grab from multiple cameras as expected, while with the other it could only grab from one camera – grabbing from the second camera would always fail. To make things stranger the mode that worked required the passing of an un-used argument to the thread function!

Here is the mode that didn’t work:

And here is the mode that does work OK, notice the dummy argument that is passed but otherwise unused!

All very strange!

Can I use std::thread from a C++/CLI project in Visual Studio 2012

This question seems to produce some confusing and contradicting answers, however the short answer to it is ‘yes, you can’.

You can use std::thread in unmanaged code in a C++/CLI project but not from managed code – but the good thing about C++/CLI is that you can mix managed and unamanaged code.

if you try to use it from managed code you will get an errors like this:

error directive: is not supported when compiling with /clr or /clr:pure.

and this:

error directive: ERROR: Concurrency Runtime is not supported when compiling /clr.

To mark a C++ file as un-managed, go to its C/C++ settings and set its ‘Common Language RunTime Support’ setting to ‘No Common Language RunTime Support’. You can also use the ‘managed’ and ‘unmanaged’ pragmas in your code to do the same, but something about mixing the two in a single file creeps me out!

Possibly the best thing to do is to keep managed code to a minimum (as it’s as ugly as sin) and just use it to interface your .NET code to your native C++ code – which can use std::thread et al. to its heart’s content!