[PATCH] D133480: [llvm-dwp] Get the DWO file using relative path instead of absolute path to make it work for distribution build

[Qing Shan Zhang via Phabricator via llvm-commits]

steven.zhang added a comment.

In D133480#3778054 <https://reviews.llvm.org/D133480#3778054>, @dblaikie wrote:

> In D133480#3777196 <https://reviews.llvm.org/D133480#3777196>, @steven.zhang wrote:
>
>> In D133480#3777059 <https://reviews.llvm.org/D133480#3777059>, @dblaikie wrote:
>>
>>> I don't think this is correct - the dwp tool might be run from a different directory than the equivalent comp_dir and so treating these as cwd-of-dwp-relative paths seems problematic.
>>>
>>> I think the correct thing to do in the situation described is for the compilation to use -fdebug-compilation-dir <https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fdebug-compilation-dir> to make the debug info portable - this will also ensure that a debugger can find the source and find the .dwo files even if they aren't packaged into a .dwp.
>>
>> Can we do it as what gdb did ? That is, getting the dwo from absolute path first, and if failed, get it from relative path ?
>
> I'm somewhat open to that, though I'd really encourage you to switch your build system/build flags so you don't have to keep adding functionality like that into other debug info consuming tools.

Thank for the suggestion, and I appreciate it. The issue of adding the build flags is that, it will pollute the remote cache. For example:

- building in workspace A: adding compilation option -fdebug-compilation-dir=path_to_workspace_A, and the objects will be cached in the remote build server.

- building in workspace B: adding compilation option -fdebug-compilation-dir=path_to_workspace_B, we cannot get the objects from remote cache though all the source code didn't change. We have to rebuild it as the compilation option changed.

If with relative path, we don't need to rebuild the objects as everything is unchanged. Remote cache is important to large project to speed up the building.

I will extend current implementation to support relative path.


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