Add Cflags.private to support static linking on Windows

[kmilos]

Cflags.private: -UINI_SHARED_LIB is needed to support both shared and static linking on Windows with a single .pc file.

See e.g. https://stackoverflow.com/a/66079443

[neheb]

@eli-schwartz any comment on this? I don't see support for this in meson.

[Tachi107]

Is this guaranteed to work? What if Cflags.private get passed after Cflags?

[kmilos]

What if Cflags.private get passed after Cflags?

That's the whole point, it doesn't work otherwise...

W/ the patched MSYS2 package:

$ pkgconf --cflags --static inih
-DINI_SHARED_LIB -UINI_SHARED_LIB

[Tachi107]

Eh, sorry, I obviously meant before, not after. Is it documented pkg-config behaviour that we could rely on? If yes, neat solution!

[kmilos]

Cflags.private is not a documented feature, and is AFAIK only implemented (and in this particular order) by pkgconf [1], and not by pkg-config. That's ok though, as this is of interest only for Windows DLLs vs static libs, and on Windows dev environnements mostly/exclusively pkgconf is available/used (MSYS2, vcpkg, etc.).

[1] https://www.msys2.org/docs/pkgconfig/#cflagsprivate-static-libraries

[Tachi107]

Il giorno ven 28 feb 2025 alle 14:05:34 -08:00:00, Miloš Komarčević ***@***.***> ha scritto:

Cflags.private is not a documented feature, and is AFAIK only implemented (and in this particular order) by pkgconf [1], and not by pkg-config.

Did a small research, and this is actually documented in the pc(5) manual page (part of pkgconf). You can read it here: <https://www.mankier.com/5/pc>. Still, the field is only documented as being used for static compilation. No guarantee of being ordered after the Cflags field is made.

That's ok though, as this is of interest only for Windows DLLs vs static libs, and on Windows dev environnements mostly/exclusively pkgconf is available/used (MSYS2, vcpkg, etc.).

pkgconf is for sure used by the vast majority (all?) of Linux distributions, but on Windows I wouldn't be so sure. Yeah, there's pkgconf, but there are also: - Strawberry perl pkg-config: https://strawberryperl.com - u-config (part of w64devkit): https://github.com/skeeto/u-config - CMake's new native .pc resolver: https://cmake.org/cmake/help/latest/command/cmake_pkg_config.html - The original FreeDesktop implementation, pkgconfiglite, and probably others, as outlined in the top StackOverflow question about installing pkg-config on Windows: https://stackoverflow.com/questions/1710922/how-to-install-pkg-config-in-windows I see the following possible alternative solutions: 1. Ask pkgconf upstream to document the behaviour you're currently observing of having Cflags.private apply after Cflags, so that it doesn't go away in the future, or 2. Do not rely on the order of options, but define a thing like -DINI_STATIC_LIB which overrides -DINI_SHARED_LIB in the C code itself.