As I said, on small projects you will see not much of a difference. When the preprocessor is doing it's business and finds an #include, it goes off loads the included file and reads the first line. It finds the guard definition and has a look to see if it is already defined. Carruagem De Fogo Partitura Pdf on this page.

I've always used both. That way, if #pragma once is supported, it will include the file only once but if not, it is ignored and will used the #ifndef method. Easy Ways to Solve Error #pragma Once In Main File Everytime you utilize the functions of your personal computer, Error #pragma Once In Main File will come your way. In the C and C++ programming languages, #pragma once is a non-standard but widely supported preprocessor directive designed to cause the current source file to be. I'd like to use '#pragma once' in my.h files instead of the old. But I get the warning symbol and the complaint '#pragma once in main file' in the left.

If it is it still has to process the file until it finds the corresponding #endif and then carry on processing the file to the end. You may find that your compiler has include guard optimisation, but I have seen results that suggest this can be improved upon. Feel free to search the net for 'external include guards', I have also seen them referred to as 'redundant include guards'. You should see various peoples experiment results.