How to debug macros efficiently in VS?

Question

I've got a pretty complicated macro inside my (unmanaged) C++ code. Is there any way to expand macros in VS debugger? Or maybe there is another way to debug macros there?

F.e. I'd like to place a breakpoint inside it.

(Yes, I know macros are bad.)

Answer 1

Go to either project or source file properties by right-clicking and going to "Properties". Under Configuration Properties->C/C++->Preprocessor, set "Generate Preprocessed File" to either with or without line numbers, whichever you prefer. This will show what your macro expands to in context. If you need to debug it on live compiled code, just cut and paste that, and put it in place of your macro while debugging.

Answer 2

I heard all possible negative answers on the topic:

• macros can only be expanded not evaluated
• preprocessor should parse also include files
• nested macros can be over-complicated
• conditional preprocessing can be tricky
• macros are evil just avoid them
• etc etc....

They are all true, but IMO they collide with the reality of everydays programming.

In fact, working on old C project, where macros were mostly simply used as functions, this became of crucial importance for me. Generating all preprocessed files with /P works, but is overkilling and time consuming. I just needed a tool that expands a simple macro defined a few lines above or at maximum in other file.

How to do that?

1. On Linux simply use GDB and his expand macros capabilities
2. On windows I use https://www.jetbrains.com/resharper-cpp/ integrated into Visual Studio

So, Yes, in a practical sense, it is possible.

Answer 3

The compiler expands macros nicely. Get a compilation listing with the macros expanded.

Insert the expanded macro into your code. Recompile and you should be able to step through it, to do a simple test.

Generally when I am building a complicated macro, I hard code it first, and test it. Then I turn it into a macro.

For 2008, this may be of help