[PATCH] D142279: [cmake] Use LLVM_ENABLE_ASSERTIONS to enable assertions in libstdc++

Mon Feb 13 12:46:01 PST 2023

dblaikie added a comment.

In D142279#4123493 <https://reviews.llvm.org/D142279#4123493>, @srj wrote:

> In D142279#4120270 <https://reviews.llvm.org/D142279#4120270>, @beanz wrote:
>
>> LLVM’s C++ interfaces do not provide a stable ABI across all configuration flags (which is not uncommon for C++). As a result llvm-config and the LLVM CMake exports provide the options LLVM was built with for the user.
>>
>> While it may be true that we could filter some of those options safely, it gets a bit tricky. Options like enabling assertions, or dump methods need to be in sync between the prebuilt LLVM and the user’s library.
>
> Yes, this. As a practical matter, code using LLVM as a library needs to know about the compiler flags and -D definitions it was built with in order to have sane ABI compatibility, unfortunately.

Specifically, assertions are intended to break ABI (so you should be able to mix/match LLVM and user code that has different LLVM assertions enabled/disabled) - there's a separate abi breaking checks macro for the cases that need abi break.

I guess by that logic we could say that LLVM assertions enabled/disabled (& libstdc++ assertions enabled/disabled) shouldn't go into llvm-config at all? Users can opt in/out of it as they see fit in their code, idnependent of how the llvm library was built? or at least keep those on-for-users by default, but the ability to configure them to not be on-by-defaeult?

Repository:
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  https://reviews.llvm.org/D142279/new/

https://reviews.llvm.org/D142279