Automatic #defines according to Debug/Release config in Visual Studio

Question

I have debug output in my program like this:

#define DEBUG
...
#ifdef DEBUG
    std::cout << \"[RE_words] \" << m_re << std::endl;
#endif
<         


        

Answer 1

The Visual Studio automatically defines _DEBUG symbol for Debug builds (and NDEBUG for non-debug builds).

Another way to do this is to go to the project settings -> configuration properties -> C/C++ -> preprocessor, and edit the preprocessor definitions manually.

See also:
This answer explains the differences between _DEBUG and NDEBUG in more detail.
This answer explains the purpose of the NDEBUG symbol and whether or not is it defined by the standard.

Answer 2

I too thought I just had to look at the preprocessor property and remove _DEBUG. Visual Studio tries to help out by setting _DEBUG if you select one of the debug run-time library options.

On the project property page Configuration Properties\C/C++\Code Generation the option selected for Runtime Library affects several defines. When selecting a debug library (/MTd or /MDd) the _DEBUG define is set.

See MSDN /MD, /MT ... for more info on the switches. There are several #defines that are set based on these options. They are pretty invisible when trying to find who sets a #define before you even include any header files!!

Answer 3

Yes, you should check project options page, Compile->Advanced compile options. However, VS by default automatically defines DEBUG directive for Debug mode.

Answer 4

Use _DEBUG. Visual C++ defines this for a Debug configuration. Check out the preprocessor directives for the Debug Configuration in your project's properties dialog.