> For an example of adding a new option see, > In any case, I agree with confirming this as a bug: all warnings should be
#pragma once is accepted for compatibility with other compilers, and enables you to use other forms of header guard coding.  Additionally, #pragma once can do the wrong thing if the same file is intentionally copied into several parts of a project, e.g. Even when #pragma once is used in an header file, the plugin incorrectly reports a diagnostic mentioning that it's being used in a main file.
It seems to be a combination of YCM and Syntastic: when either is unloaded, it doesn't happen; when both are loaded, it does.
http://llvm.org/bugs/show_bug.cgi?id=16686, Workaround for annoying clang bug with pragma once. We use optional third-party analytics cookies to understand how you use GitHub.com so we can build better products. privacy statement. Not clear to me if this should be hidden always, then it could be done just through the errorformat. Already on GitHub? You can disable the warning by setting "clang.cxxflags": ["-Wno-pragma-once-outside-header"]. a file program contained in a single .cpp file) get this warning warning: #pragma once in main file Makes sense does it not?
they're used to gather information about the pages you visit and how many clicks you need to accomplish a task. Using VSCode 1.22.2 and C/c++-Extension 0.16.1 If I write a simple header file like Abc.h and insert a modern include-guard #pragma once I am getting the very annoying warning: #pragma once in main file. Sign in
It can do this efficiently and safely.  Thus, #pragma once serves the same purpose as include guards, but with several advantages, including: less code, avoidance of name clashes, and sometimes improvement in compilation speed. We’ll occasionally send you account related emails. Comments.
xcpp programs can use other programs (xcpp files) or libs (xhpp files).
> controllable by a -Wxxx option. `#pragma once` was originally intended to provide functionality that is a bit different from what include guards do. > compiling it as the TU itself? It requires less typing, is less distracting, and can't cause symbol collisions, errors caused when different header files use the same preprocessor symbol as the guard value.
It can occur in complex projects when file system aliasing or aliased include paths prevent the compiler from identifying identical include files by canonical path. We use optional third-party analytics cookies to understand how you use GitHub.com so we can build better products. Successfully merging a pull request may close this issue. However, ARM recommends to use #ifndef and #define coding because this is more portable. they're used to gather information about the pages you visit and how many clicks you need to accomplish a task. this problem still exists and there is not flag to disable this behaviour, its kind of annoying :/, Clang bug causing this: http://llvm.org/bugs/show_bug.cgi?id=16686. If the same file is included again, the preprocessor would realize it just by looking at the name. As a user, there is no room for mistakes.
Over-reliance upon either mechanism on the part of programmers by direct, unprotected use of #include directives without their own #include guard will lead to failure when using an include file that has not protected itself with either mechanism. , Identifying the same file on a file system is not a trivial task.
The #include directive is defined to represent a programmer's intention to actually include the text of a file at the point of the directive. 9.90 #pragma once Enable the compiler to skip subsequent includes of that header file. Copy link Quote reply jhasse commented Jul 5, 2015.
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We use essential cookies to perform essential website functions, e.g. The idea was that `#pragma once` would permit the preprocessor to cache the names of already-included files. You signed in with another tab or window. I'm sorry if I am doing something wrong, but I do not see what.
When I run neomake inside a .h file, I get the warning: I do indeed use this pragma in the header files, but it seems that the compilers somehow think that the file is not a header. By using the pragma, the compiler should not need to open the file and scan for its contents, processing the include guards.
Using #pragma once allows the C preprocessor to include a header file when it is needed and to ignore an #include directive otherwise. It's called the multiple-include optimization. For example.
I guess the "generated cpp with sole #include" approach is not that bad.
This has the effect of altering the behavior of the C preprocessor itself, and allows programmers to express file dependencies in a simple fashion, obviating the need for manual management.
The most common alternative to #pragma once is to use #define to set an #include guard macro, the name of which is picked by the programmer to be unique to that file. This is a clang issue, not a YCM issue.
Moreover, the files using these headers are marked as being affected as well in the explorer sidebar, and so on and so forth. See: A workaround would simply be to check the extension of the current fail and get rid of the diagnostic if it's an header.
This can easily spread over a significant part of the workspace, which is quite irritating. In the absence of #include guards around #include directives, the use of #pragma once will improve compilation speed for some compilers since it is a higher-level mechanism; the compiler itself can compare filenames or inodes without having to invoke the C preprocessor to scan the header for #ifndef and #endif. An option to disable warning "#pragma once in main file", > Testcase: The compiler recognizes the include guard idiom, and implements the multiple-include optimization the same way as the #pragma once directive if no non-comment code or preprocessor directive comes before or after the standard form of the idiom: We recommend the include guard idiom when code must be portable to compilers that don't implement the #pragma once directive, to maintain consistency with existing code, or when the multiple-include optimization is impossible.