[all-commits] [llvm/llvm-project] 068757: [C++20][Modules][HU 2/5] Support searching Header ...

[iains via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0687578728ea1985cbab0de14d4eeb4e89cdf210
      https://github.com/llvm/llvm-project/commit/0687578728ea1985cbab0de14d4eeb4e89cdf210
  Author: Iain Sandoe <iain at sandoe.co.uk>
  Date:   2022-03-26 (Sat, 26 Mar 2022)

  Changed paths:
    M clang/include/clang/Basic/DiagnosticDriverKinds.td
    M clang/include/clang/Frontend/FrontendOptions.h
    M clang/lib/Frontend/CompilerInvocation.cpp
    M clang/lib/Frontend/FrontendAction.cpp
    A clang/test/Modules/cxx20-hu-02.cpp
    A clang/test/Modules/cxx20-hu-03.cpp
    A clang/test/Modules/cxx20-hu-bad-input.cpp

  Log Message:
  -----------
  [C++20][Modules][HU 2/5] Support searching Header Units in user or system search paths.

This is support for the user-facing options to create importable header units
from headers in the user or system search paths (or to be given an absolute path).

This means that an incomplete header path will be passed by the driver and the
lookup carried out using the search paths present when the front end is run.

To support this, we introduce file fypes for c++-{user,system,header-unit}-header.
These terms are the same as the ones used by GCC, to minimise the differences for
tooling (and users).

The preprocessor checks for headers before issuing a warning for
"#pragma once" in a header build.  We ensure that the importable header units
are recognised as headers in order to avoid such warnings.

Differential Revision: https://reviews.llvm.org/D121096