[PATCH] D44560: [DWARF] Rework debug line parsing to use llvm::Error and callbacks

[Rafael Avila de Espindola via llvm-commits]

David Blaikie via llvm-commits <llvm-commits at lists.llvm.org> writes:

> On Mon, Mar 19, 2018 at 2:52 PM Rafael Avila de Espindola via Phabricator <
> reviews at reviews.llvm.org> wrote:
>
>> espindola added a comment.
>>
>> One thing that I am probably missing is why we need this much.
>>
>> On the lld side we only read this section when there is an error, and if
>> reading it fails we just want to print the extra info to the user.
>>
>> My guess is that something like lldb would be similar, read the line table
>> and print a message if it failed.
>>
>> For both cases a simple Expected<> should be sufficient, no?
>>
>
> Mostly probably for things like llvm-dwarfdump that are likely to want to
> provide more info to the user than to halt at the first error - to aid in
> debugging/investigation.

OK, dwarfdump is probably the best example as it wants to print as much
as possible.

But even for dwarfdump it seems that this could be "just":

Expected<const DWARFDebugLine::LineTable *> getOrParseLineTable(
    DWARFDataExtractor &DebugLineData, uint32_t Offset, const DWARFContext &Ctx,
    const DWARFUnit *U,
    std::function<Error(StringRef)> RecoverableIssueCallback);

The idea is that every time the parser gets in a situation where it finds
something it doesn't understand but can recover from (new version of a
field, but we can skip over it for example) it can do something like

if (Error E = RecoverableIssueCallback("unknown version of foobar"))
   return E;

The default callback, which would, for exmaple, be used by lld, could
just always return an error.

The callback used by dwarfdump would just log the issure and return
success.

Cheers,
Rafael