RFR: 8293422: DWARF emitted by Clang cannot be parsed

[Christian Hagedorn]

On Wed, 21 Sep 2022 10:47:38 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Thanks Thomas for that link. I was not aware of this `-gdwarf-aranges` flag. I've tried it out and it indeed seems to work. But I was not able to build with `-flto=thin` as it resulted in build failures. So, I'm not sure what would happen and if it's even possible to build with it in general. Nevertheless, I suggest to go with that `-gdwarf-aranges` flag solution for now and remove the previously suggested bailout fix for Clang.
>> 
>> However, `-gdwarf-aranges` (and `-gdwarf-4` which I think we should also add to avoid getting the unsupported DWARF 5 format) was only added in Clang 5.0. But we must support down to 3.5 according to:
>> https://github.com/openjdk/jdk/blob/cb72f80925965c73e32c44ce3196866272306d7f/doc/building.md?plain=1#L353-L354
>> 
>> I therefore changed the previous complete bailout fix to a bailout fix for Clang versions older than 5.0.
>> 
>> I've noticed that Clang is emitting a full relative path for the filename in the form of `src/hotspot/share/compiler/compilerThread.cpp:58` with debug builds (it only emits the filename with release builds). I therefore added an additional method `strip_path_prefix()` to get rid of the path prefix.
>
>> Thanks Thomas for that link. I was not aware of this `-gdwarf-aranges` flag. I've tried it out and it indeed seems to work. But I was not able to build with `-flto=thin` as it resulted in build failures. 
> 
> I only thought that maybe we do compile with `-flto=thin` already, and so we could not use these flags.
> 
>>So, I'm not sure what would happen and if it's even possible to build with it in general. Nevertheless, I suggest to go with that `-gdwarf-aranges` flag solution for now and remove the previously suggested bailout fix for Clang.
> 
> I agree.
> 
>> 
>> However, `-gdwarf-aranges` (and `-gdwarf-4` which I think we should also add to avoid getting the unsupported DWARF 5 format) was only added in Clang 5.0. But we must support down to 3.5 according to:
>> 
>> https://github.com/openjdk/jdk/blob/cb72f80925965c73e32c44ce3196866272306d7f/doc/building.md?plain=1#L353-L354
>> 
>> I therefore changed the previous complete bailout fix to a bailout fix for Clang versions older than 5.0.
>> 
>> I've noticed that Clang is emitting a full relative path for the filename in the form of `src/hotspot/share/compiler/compilerThread.cpp:58` with debug builds (it only emits the filename with release builds). I therefore added an additional method `strip_path_prefix()` to get rid of the path prefix.
> 
> Okay.

Thanks @tschatzl for reviewing it again!

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PR: https://git.openjdk.org/jdk/pull/10287