__FILE__, __LINE__, and __FUNCTION__ usage in C++

c++ debugging logging c-preprocessor
Runcible picture Runcible · Feb 28, 2009 · Viewed 248.3k times · Source

Presuming that your C++ compiler supports them, is there any particular reason not to use __FILE__, __LINE__ and __FUNCTION__ for logging and debugging purposes?

I'm primarily concerned with giving the user misleading data—for example, reporting the incorrect line number or function as a result of optimization—or taking a performance hit as a result.

Basically, can I trust __FILE__, __LINE__ and __FUNCTION__ to always do the right thing?

Answer

Evan Teran picture Evan Teran · Feb 28, 2009

__FUNCTION__ is non standard, __func__ exists in C99 / C++11. The others (__LINE__ and __FILE__) are just fine.

It will always report the right file and line (and function if you choose to use __FUNCTION__/__func__). Optimization is a non-factor since it is a compile time macro expansion; it will never effect performance in any way.

Related questions

Logging values of variables in Android native ndk

I set up logging with C++ in Android NDK. I can print a message to logcat like this: __android_log_write(ANDROID_LOG_INFO, "tag here", "message here"); Now let's say I have an integer called testint. How can I …

Read More
Adding message to assert

Hallo! I'm looking for a way to add custom messages to assert statements. I found this questions Add custom messages in assert? but the message is static there. I want to do something like this: assert((0 < x) && (…

Read More
Debugging with command-line parameters in Visual Studio

I'm developing a C++ command-line application in Visual Studio and need to debug it with command-line arguments. At the moment I just run the generated EXE file with the arguments I need (like this program.exe -file.txt) , but this …

Read More