[all-commits] [llvm/llvm-project] 466ea8: [lldb] Fix failures when evaluating C++ expression...

[Med Ismail Bennani via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 466ea89fc6d8bfd197cbc1055bbc38e730e9d523
      https://github.com/llvm/llvm-project/commit/466ea89fc6d8bfd197cbc1055bbc38e730e9d523
  Author: Med Ismail Bennani <ismail at bennani.ma>
  Date:   2023-09-29 (Fri, 29 Sep 2023)

  Changed paths:
    M lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

  Log Message:
  -----------
  [lldb] Fix failures when evaluating C++ expression and loading modules

This patch tentatively fixes the various test failures introduced
following 0ea3d88bdb16:

https://green.lab.llvm.org/green/view/LLDB/job/as-lldb-cmake/6316/

>From my understanding, the main issue here is that we can't find some headers
when evaluating C++ expressions since those headers have been promoted
to be system modules, and to be shipped as part of the toolchain.

Prior to 0ea3d88bdb16, the `BuiltinHeadersInSystemModules` flag for in
the clang `LangOpts` struct was always set, however, after it landed,
the flag becomes opt-in, depending on toolchain that is used with the
compiler instance. This gets set in `clang::createInvocation` down to
`Darwin::addClangTargetOptions`, as this is used mostly on Apple platforms.

However, since `ClangExpressionParser` makes a dummy `CompilerInstance`,
and sets the various language options arbitrarily, instead of using the
`clang::createInvocation`, the flag remains unset, which causes the
various error messages:

```
AssertionError: 'error: module.modulemap:96:11: header 'stdarg.h' not found
   96 |    header "stdarg.h" // note: supplied by the compiler
      |           ^
```

Given that this flag was opt-out previously, this patch brings back that
behavior by setting it in lldb's `ClangExpressionParser` constructor,
until we actually decide to pull the language options from the compiler driver.

Signed-off-by: Med Ismail Bennani <ismail at bennani.ma>