[Lldb-commits] [PATCH] D141330: [lldb] Limit 8b259fe573e1 to dSYMs

Thu Jan 12 04:50:41 PST 2023

labath added a comment.

Just to clarify: I was responding to the question about the ELF file usage, not questioning the overall approach. Given that MachO has a special code for dsym files, I think it makes sense to use it.

In D141330#4043807 <https://reviews.llvm.org/D141330#4043807>, @jasonmolenda wrote:

>   By scanning the table, a debugger can quickly decide which compilation unit to look in to find the debugging information for an object that has a given address.
>   
>   If the range of addresses covered by the text and/or data of a compilation unit is not contiguous, then there may be multiple address range descriptors for that compilation unit.
>
> (I dislike it when the standard says "there MAY be multiple address range descriptors" -- does this mean if I have a noncontiguous CUs A and B interleaved in the final binary, the debug_aranges can overlap?)

I see what you mean, but I wouldn't really read it that way, and I hope nobody produces files like that.

> There's no guarantee for (1) if a debug_aranges table is present, but maybe we can simply assume that any producer producing debug_aranges has done so comprehensively.  I couldn't imagine why it wouldn't be that way.

We can't do that because, as I alluded to in the other comment, the aranges section can be produced by the compiler, and there's no guarantee that all CUs will be built with the same flags (so some may be missing that section). In the elf world a linker will just concatenate those sections without trying to fill in the blanks.

A normal binary includes some code from the system runtime (which is built by the OS vendor not the user). Typically, that code will not have debug info, but sometimes it does, and in that case it's pretty much guaranteed that it will be built using different compiler/flags than the user code.

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