[PATCH] D106084: [DebugInfo] Switch to using constructor homing (-debug-info-kind=constructor) by default when debug info is enabled

Tue Jul 20 09:27:11 PDT 2021

jmorse accepted this revision.
jmorse added a comment.

In D106084#2887702 <https://reviews.llvm.org/D106084#2887702>, @dblaikie wrote:

> It'd be preferable not to split these two cases (current "limited" versus "ctor" homing) - because they rely on the same assumption, that the whole program is built with debug info (hence the renaming of "limited" a long time ago to "standalone-debug" to create a policy/philosophy around what goes in each category).
>
> Wouldn't the current "limited" behavior have problems for this shared libraries situation too? Sounds like in that case -fstandalone-debug should be used.

I had a dig into what "limited" currently does -- and I think Windows most closely matches our setup. Many portions don't have the source available, the debugger behaves similarly, and the default debug-info mode there is "Limited". I think what saves our bacon is the import/export clause [0, 1], if a class is used between libraries then neither Limited or Constructor debug-info will suppress its class definition.

With that in mind, I suppose we'll be alright with constructor homing on by default. The interfaces between libraries will still have type information emitted in Constructor mode, and it's not excessive for those who want to dig deeper to run with standalone-debug.

[0] https://github.com/llvm/llvm-project/blob/4a30a5c8d9f0fa8a4b6ebd7c82d5335ae7a77521/clang/lib/CodeGen/CGDebugInfo.cpp#L2391
[1] https://github.com/llvm/llvm-project/blob/4a30a5c8d9f0fa8a4b6ebd7c82d5335ae7a77521/clang/lib/CodeGen/CGDebugInfo.cpp#L2346

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