[PATCH] D69122: Add support to find out resource dir and add it as compilation args

[Kousik Kumar via Phabricator via cfe-commits]

kousikk added a comment.

> I haven't looked into this in detail but it feels kind of wasteful to start a process just to get this value.

Right, that's why I cache this information. So multiple compile commands sharing the same compiler process will trigger at 1 subprocess and then subsequently use the cached information.

>   Can't we just expose it in some of the clang libs we already link against?

The problem is, the value of `resource-dir` depends on `CLANG_VERSION` and `ARCH` #define's, that's set when the clang binary is built. So lets say you use `/home/kousikk/clang/7.0/bin/clang`, then if your compilation database is:

  [
    { "command": "/home/kousikk/clang/7.0/bin/clang -c /home/kousikk/test.cpp",
      "file": "/home/kousikk/test.cpp",
      "directory": "/home/kousikk/"
    }
  ]

then the value of `-resource-dir` for compilation of `test.cpp` must be something like `/home/kousikk/clang/7.0/lib64/clang/7.0.0/`. Any libs used as part of building `clang-scan-deps` itself is going to point to its own resource-directory which is NOT the behaviour we want.

-------

> could we please add support for generic -extra-arg, which can then add -resource-dir like the other clang tools?

@arphaman would this be an option to `clang-scan-deps`? If so it might not work since commands in the compilation-database can be using more than 1 version of clang?

In addition, every project on which we use scan-deps will inturn have to specify this extra argument - wouldn't it be better if they didn't have to do that?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D69122/new/

https://reviews.llvm.org/D69122