[Proposal] Add first-class support for compiler feature/ABI tests

[cyanidle]

1. ABI-test from build system itself: Like CMake does for CMAKE_SIZEOF_VOID_P, CMAKE_CXX_COMPILER_ID etc.
2. User-defined feature tests (sizeof(double), check_header())

Bonus:

1. Also such tests could be cached (like CMake does it). To perform these stable checks only once (not on each file added to project)

2. I would like to make this parallel-able. I am very tired of autoconf configure script (and CMake ones too) doing feature-detecting (by compiling programs, that test for sizeof(double) for example) longer, than the project itself builds.

I would try to PR some of this functionality, if you don`t mind (starting with basic Compiler detection stuff)

[cyanidle]

The second "bonus" one is the one I am actually passionate about, wanted to try to make result of suck checks "lazy" to allow batching multiple independent compilability checks at the same time

[TomasBorquez]

Doable, let's keep it simple for now and with compiler detection and basic size checks as you said, we can cache it and make it parallel later, something like TestSizeAsync/TestSizeSync maybe?

[cyanidle]

I think we should not implement specific APIs for TextXXX(). We should just make TestCompiles/TestLinks/TestHasSymbol (just mimic CMake analogs). For now lets not deal with Async stuff.

On the topic of CMake: it allows specifying headers and libraries provided from dependencies. We should return to that, once dependencies management is stabilized.

[TomasBorquez]

I think we should not implement specific APIs for TextXXX(). We should just make TestCompiles/TestLinks/TestHasSymbol (just mimic CMake analogs). For now lets not deal with Async stuff.

On the topic of CMake: it allows specifying headers and libraries provided from dependencies. We should return to that, once dependencies management is stabilized.

Agreed, when we start implementing this we can look into it

[NHOrus]

How about https://github.com/tavianator/parconf ?
https://tavianator.com/2025/configure.html for explanation of what this thing is doing.

[cyanidle]

God damn, thats what I meant! But in this case this should just create a jobs graph using ninja files, then run them to get configure result for all checks.

It is a difficult problem, because not only other configure checks may depend on one before them (causing serialized wait), but also branches in build script itself.

This can be solved by restricting usage of "CheckCompiles" and making it declarative. To run all checks at the start of configuration