[PATCH] D157283: [clang] Match -isysroot behaviour with system compiler on Darwin

Tue Sep 19 13:56:35 PDT 2023

DmitryPolukhin added a comment.

In D157283#4648242 <https://reviews.llvm.org/D157283#4648242>, @ldionne wrote:

> As explained in https://reviews.llvm.org/D89001#4648241, upstream Clang is the way it should be right now. The intent is that we first look along the `clang` binary for headers (that way if you install a custom libc++ it will be picked up), and then we fall back to the SDK version. It's just unfortunate that AppleClang has lagged behind a bit and created some confusion, but I believe the latest release should have the exact same behavior as upstream Clang wrt search paths. The commit mentioned above (`9edb9a711503d540cf3126c0fde11ce9a0d9a7aa`) as actually just making downstream back in sync with upstream. So IMO the correct thing to do is to abandon this change and wait for a new AppleClang that has matching behavior with upstream Clang (it's probably in Xcode 15 RC which came out recently).

@ldionne thank you for the reply. Unfortunately current behaviour makes problems for clang-tools like clang-tidy and clangd that read CDBs from `compile_commands.json`. They start looking headers relative to compiler path specified in CDB but it is better to use path specified in -isysroot (it is what user expects when they specify the option). What is the rationale behind ignoring `-isysroot` specified in command line? If user would like to use search path relative to compiler, they could just remove `-isysroot` and get this behaviour.

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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D157283/new/

https://reviews.llvm.org/D157283