Should I always use pragma once?
I recommend using #pragma once instead of old macro-based header guards. It will reduce the number of preprocessor macros and prevent potential and hard to find compilation problems. You should also replace existing macro-based header guards with this statement if you do maintenance work on existing code.
Is pragma once standard C++?
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 included only once in a single compilation. …
Does pragma once work in g ++?
Meanwhile, there are a lot of compilers that understand #pragma once. Most modern and relevant compilers support it, at least VC++, g++, clang, Intel. To be on the safe side, you should still prefer the classical header guards — #pragma once is not C++ standard, and no compiler is forced to support it.
What does pragma once mean in C++?
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 included only once in a single compilation.
Why pragma once is bad?
#pragma once has no such safety net — if the compiler is wrong about the identity of a header file, either way, the program will fail to compile. If you hit this bug, your only options are to stop using #pragma once , or to rename one of the headers.
Should I use pragma once C++?
We recommend the #pragma once directive for new code because it doesn’t pollute the global namespace with a preprocessor symbol. It requires less typing, it’s less distracting, and it can’t cause symbol collisions.
What does pragma do C++?
A pragma is a compiler directive that allows you to provide additional information to the compiler. This information can change compilation details that are not otherwise under your control. For example, the pack pragma affects the layout of data within a structure. No pragmas are defined by the C++ standard.
Why is pragma once not standard?
#pragma once is a non-standard pragma that is supported by the vast majority of modern compilers. Unlike header guards, this pragma makes it impossible to erroneously use the same macro name in more than one file.
Where should I use pragma once?
#pragma once is less prone to making mistakes and it is less code to type. To speed up compile time more just forward declare instead of including in . h files when you can. I prefer to use #pragma once .
Where can I use pragma once?
#pragma once is a preprocessor directive used to prevent header files from being included multiple times. The #pragma once directive, once present in a file, assures that the file will not be included multiple times in the current project.
What does pragma stand for?
Pragma is short for pragmatic information. So, simple. In plain English, pragmatic is an adjective that means sensible and practical.