LLVM libc used its own definition of LIBC_ASSERT in libc++

[ldionne]

Since hand-in-hand, libc++ uses llvm-libc to implement std::from_chars. That's done via a "shared" layer where llvm-libc provides functions that intent to be pretty self-contained.

However, this layer includes libc/src/__support/libc_assert.h, which provides its own definition of LIBC_ASSERT based on assert. In libc++, we have our own assertion macro and we would like to use that instead of libc's own definition. Hence, LIBC_ASSERT would have to be lifted to something that can be customized by libc++ (and perhaps users generally speaking, IDK).

Does that seem fine? Do you have any preference about how to achieve that?

[ldionne]

CC @michaelrj-google

[llvmbot]

@llvm/issue-subscribers-libc

Author: Louis Dionne (ldionne)

Since hand-in-hand, libc++ uses llvm-libc to implement `std::from_chars`. That's done via a "shared" layer where llvm-libc provides functions that intent to be pretty self-contained.

However, this layer includes libc/src/__support/libc_assert.h, which provides its own definition of LIBC_ASSERT based on assert. In libc++, we have our own assertion macro and we would like to use that instead of libc's own definition. Hence, LIBC_ASSERT would have to be lifted to something that can be customized by libc++ (and perhaps users generally speaking, IDK).

Does that seem fine? Do you have any preference about how to achieve that?

[michaelrj-google]

A simple temporary solution would be for us to add a flag like LIBC_COPT_EXTERNAL_LIBC_ASSERT that means we don't define LIBC_ASSERT at all. We could look into designing a more robust system in future.

[lntue]

We could provide such defaults for shared configs in https://github.com/llvm/llvm-project/blob/main/libc%2Fshared%2Flibc_common.h