The debug mode has been broken pretty much ever since it was shipped because it was possible to enable the debug mode in user code without actually enabling it in the dylib, leading to ODR violations that caused various kinds of failures. This commit makes the debug mode a knob that is configured when building the library and which can't be changed afterwards. This is less flexible for users, however it will actually work as intended and it will allow us, in the future, to add various kinds of checks that do not assume the same ABI as the normal library. Furthermore, this will make the debug mode more robust, which means that vendors might be more tempted to support it properly, which hasn't been the case with the current debug mode. This patch shouldn't break any user code, except folks who are building against a library that doesn't have the debug mode enabled and who try to enable the debug mode in their code. Such users will get a compile-time error explaining that this configuration isn't supported anymore. In the future, we should further increase the granularity of the debug mode checks so that we can cherry-pick which checks to enable, like we do for unspecified behavior randomization. Differential Revision: https://reviews.llvm.org/D122941
libc++ / libc++abi configuration caches
This directory contains CMake caches for the supported configurations of libc++. Some of the configurations are specific to a vendor, others are generic and not tied to any vendor.
While we won't explicitly work to break configurations not listed here, any configuration not listed here is not explicitly supported. If you use or ship libc++ under a configuration not listed here, you should work with the libc++ maintainers to make it into a supported configuration and add it here.
Similarly, adding any new configuration that's not already covered must be discussed with the libc++ maintainers as it entails a maintenance burden.