[all-commits] [llvm/llvm-project] 1cbcf7: [lldb][ClangExpressionParser] Set BuiltinHeadersIn...

[Michael Buch via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1cbcf74083e92021472ec9644b88418f377ce550
      https://github.com/llvm/llvm-project/commit/1cbcf74083e92021472ec9644b88418f377ce550
  Author: Michael Buch <michaelbuch12 at gmail.com>
  Date:   2024-08-07 (Wed, 07 Aug 2024)

  Changed paths:
    M lldb/include/lldb/Utility/XcodeSDK.h
    M lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp
    M lldb/source/Utility/XcodeSDK.cpp

  Log Message:
  -----------
  [lldb][ClangExpressionParser] Set BuiltinHeadersInSystemModules depending on SDK version (#102309)

This patch changes the way we initialize `BuiltinHeadersInSystemModules`
which is one of the flags controlling Clang's behaviour when the Darwin
module is split into more fine-grained modules. The
ClangExpressionParser currently unconditionally sets
`-fbuiltin-headers-in-system-modules` when evaluating expressions with
the `target.import-std-module` setting. This flag should, however, be
set depending on the SDK version (which is what the Clang Darwin
toolchain does).

Unfortunately, the compiler instance that we create with
`ClangExpressionParser` never consults the Clang driver, and thus
doesn't correctly infer `BuiltinHeadersInSystemModules`. Note, this
isn't an issue with the `CompilerInstance` that the
`ClangModulesDeclVendor` creates because it uses the `createInovcation`
API, which calls into `Darwin::addClangTargetOptions`.

This patch mimicks how `sdkSupportsBuiltinModules` is used in
`Darwin::addClangTargetOptions`.

This ensures that the `import-std-module` API tests run cleanly
regardless of SDK version.

The plan is to eventually make the `CompilerInstance` construction in
`ClangExpressionParser` go through the driver, so we can avoid
duplicating the logic in LLDB. But we aren't there yet.

**Implementation**
* We look for the `SDKSettings.json` in the sysroot directory that we
found in DWARF (via `DW_AT_LLVM_sysroot`)
* Then parse this file and extract the SDK version number out of it
* Then mimick `sdkSupportsBuiltinModules` from `Toolchains/Darwin.cpp`
and set `BuiltinHeadersInSystemModules` based on it

rdar://116490281



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