add _ENFORCE_ONLY_CORE_HEADERS

[fsb4000]

Fixes #311

These are probably terrible error messages.
Feel free to suggest a better :)

As far as I remember, I already asked. But I still want to clarify. We can't create a failing test. They are only available in the LLVM test suite, right?

[miscco]

We are using lit to run the test. Did you try a test.compile.fail.cpp

[fsb4000]

Did you try a test.compile.fail.cpp

no.

Can I have 2 failing tests in 1 folder?

One for _FORBID_ALL_STL_HEADERS, one for _ENFORCE_ONLY_CORE_HEADERS?

[miscco]

I do not know, but you can always just add two folders i guess

[fsb4000]

No. It doesn't work.

When I have test.compile.fail.cpp, I get:

python tests\utils\stl-lit\stl-lit.py ..\..\..\tests\std\tests\GH_000311_enforce_core_headers
stl-lit.py: C:\Dev\STL\llvm-project\llvm\utils\lit\lit\discovery.py:267: warning: input '..\\..\\..\\tests\\std\\tests\\GH_000311_enforce_core_headers' contained no tests
error: did not discover any tests for provided path(s)

[AdamBucior]

We need to verify that all non-core headers include yvals.h instead of yvals_core.h.

STL/stl/inc/algorithm

Line 9 in bd7adb4

#include <yvals_core.h>

[fsb4000]

@miscco I found two links:

STL/tests/std/lit.site.cfg.in

Line 15 in bd7adb4

config.suffixes = ['test[.]cpp$', 'test[.]compile[.]pass[.]cpp$']

https://github.com/llvm/llvm-project/blob/4e52a04833fb352090498d6d1c013a2c61d75e53/libcxx/test/configs/legacy.cfg.in#L45

So with default configuration we can't create a failing test. But I think it's possible with a custom python script...

[StephanTLavavej]

We made a decision on #311 in the weekly maintainer meeting - let's keep _ENFORCE_ONLY_CORE_HEADERS but drop the _FORBID_ALL_STL_HEADERS functionality, since we haven't found a compelling user scenario for that.

[StephanTLavavej]

Thanks! (And apologies for the extreme delay here. 🙀) I've pushed changes to use the new STL error message machinery, to perform this check for only real compilers (non-compiler tools have "preprocessors" with sometimes questionable behavior), and to fuse the test coverage into the pre-existing test for core headers where this makes perfect sense.

Users will see:

D:\GitHub\STL>type meow.cpp
#include <vector>
int main() {}

D:\GitHub\STL>cl /EHsc /nologo /W4 /D_ENFORCE_ONLY_CORE_HEADERS meow.cpp
meow.cpp
D:\GitHub\STL\out\build\x64\out\inc\yvals.h(14): error STL1005: Tried to include a non-core C++ Standard Library header file with _ENFORCE_ONLY_CORE_HEADERS defined.
D:\GitHub\STL\out\build\x64\out\inc\yvals.h(13): error C2338: static_assert failed: 'Error in C++ Standard Library usage.'

[StephanTLavavej]

I'm speculatively mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

[StephanTLavavej]

Thanks for making it easier for users to limit themselves to the core subset! 🎯 ✅ 🎉