how to debug a release version of library in Visual Studio

Question

I need to debug the release version of my linked library. I am already generating debug information with my release build following this article but how can I do the same with the library project? Note that library project doesn't have link page in properties where debug information is created in the link above. I am using VS2010.

What I really want is to make TRACE work whlile debugging the library. I tried to link debug version of library with the release exe but it creates linker errors.

Answer 1

What I really want is to make TRACE work...

You mean the MFC TRACE macro? The one that writes messages to the debug/output window of the debugger?

Unfortunately, even if you do fix your build settings so that your final executable contains debug information for your static library it won't bring back those trace statements. TRACE is a macro and therefore is handled by the compiler preprocessor. When you compile in release mode, that macro is redefined to be a no-op. It's as if the TRACE statement was deleted from the source code.

Even if you do resolve the problem of adding debug symbols to your library and executable, it won't bring those trace statements back. They were removed during the compile phase.

So what to do? Turns out, if you dig deep enough into those macros, they are ultimately calling a Win32 function OutputDebugString. This call is available in both debug and release versions of the ms libraries. So ... you could replace the trace macros with explicit calls to OutputDebugString - it's not as convenient to code with but at least you will get your debug output in release mode.

BTW, I finally gave up on all those macros years ago and we have completely replaced them with log4cplus calls. Any logging framework would be better than the trace macros - because the time when you really need tracing is not when you are debugging but when your code is in production and you cannot reproduce the problem locally. It's much better to log to a file which the customer can send to you, then rely on tracing that only works in the debugger. Something to consider anyways...

Answer 2

A static library isn't linked, so it's no surprise that linker options are unavailable. You basically just need to tell the compiler to produce debugging information. From there, creating the library is little more than putting a bunch of object files together into a single file.

So basically, just tell the compiler to produce debug information, and the library will contain debug info.