On Tue, Mar 05, 2024 at 10:43:50AM +0000, Volker Hilsheimer via Development wrote: > > On 4 Mar 2024, at 15:56, Kai Köhne via Development > > <development@qt-project.org> wrote: > > > Hi Marc, > > I've nothing against using '#pragma once' for private/internal headers. > > But you said you mainly want to have this to differentiate between > > different types of headers. If this is the motivation, I think we can > > make this differentiation even more explicit. For instance, public > > headers could get a > > // This header is part of the public Qt API. > > comment. Much like the 'We mean it', or 'pragma once', syncqt could > > enforce this for public headers, and error out if it's used for > > non-public ones. > > Kai > > I think the challenge then is again how syncqt can know what a public > header is. How does syncqt know that src/plugins/**/*.h headers are not > public headers? They look like public headers, except for the “plugins” > in the path. How do we, on a build system level, distinguish between > “private installed” and “private non-installed” headers?
Opt-in by a specific comment "// This is a public/private/... header" sounds like an option to me. > In the end, syncqt can ideally rely on an explicit decision that has > become manifest through an easily recognizable pattern in each header > file. Whether we replace include guards with #pragma in all non-public > headers, or tag all public headers with a comment doesn’t really matter > all that much, does it? > > But given that we have the “We mean it” comment already for _p.h > headers, would it not be more consistent if we simply add that comment > to all non-public headers (no matter their file path, and no matter > whether the header is installed or not)? That comment makes the > usability of the declarations in the header obvious to the reader, > without having to know the rules. > > We have agreed that for some headers we allow use of #pragma, but > taking myself as a reference, I doubt that it’s obvious to everyone > which headers are installed, and when it’s allowed to use #pragma, and > when it’s mandatory to use #pragma. Perhaps adding the “We mean it” > comment to all headers not declaring public API is less obscure? The > question is if and how we can use syncqt to enforce this reliably. Even if we find out that there's a 1:1 relation between "#pragma once" and private headers I also think it's worthwhile to make that explicit. Andre' -- Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
