2005997 - Enforce _LIBCPP_REMOVE_TRANSITIVE_INCLUDES for libcxx

Status: RESOLVED FIXED

(Firefox Build System :: General, task)

Description

[[:sergesanspaille]]

When set, _LIBCPP_REMOVE_TRANSITIVE_INCLUDES informs libcxx that transitive inclusion of standard headers must be removed, which should enable faster build and conforms to the general practice of including explicitly what we use instead of relying on implicit dependencies.

Comment 1

[[:sergesanspaille]]

As a side note: I've measured the impact in terms of preprocessed lines removed and it's currently super low (a thousand lines, a drop in the ocean).
That being said, it also detected an implicit dependency (see Bug 2005998), so it's good to have for that aspect.

Comment 2

[[:sergesanspaille]]

Attachment: Bug 2005997 - Enable _LIBCPP_REMOVE_TRANSITIVE_INCLUDES for libcxx r=cpeterson!

See https://libcxx.llvm.org/DesignDocs/HeaderRemovalPolicy.html for the
design document, but basically this should make header dependencies less
costly in terms of compilation time.

Comment 3

[Chris Peterson [:cpeterson]]

clang defines _LIBCPP_REMOVE_TRANSITIVE_INCLUDES when compiling with -std=c++23, so fixing these transitive include errors is a blocker to updating from C++23.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/877cf3739239
https://hg.mozilla.org/mozilla-central/rev/930fefd02854
Enable _LIBCPP_REMOVE_TRANSITIVE_INCLUDES for libcxx r=glandium

Comment 5

[agoloman]

https://hg.mozilla.org/mozilla-central/rev/930fefd02854