[PATCH] D81063: [DWARFYAML][debug_aranges] Replace InitialLength by Format and Length.

[Xing GUO via Phabricator via llvm-commits]

Higuoxing marked an inline comment as done.
Higuoxing added inline comments.


================
Comment at: llvm/include/llvm/ObjectYAML/DWARFYAML.h:68
+  llvm::dwarf::DwarfFormat Format;
+  uint32_t LengthPrefix;
+  uint64_t Length;
----------------
jhenderson wrote:
> I wouldn't bother with a length prefix. I'm not sure it's important for testing, because either the parser will read the DWARF64 marker (i.e. 0xffffffff) and treat the next 8 bytes as the rest of the length, or it won't in which case, it will treat those 4 bytes as the actual length, regardless of their value (with possible exceptions for the rest of the reserved range, but those values can be entered as the length in the YAML document anyway).
Sorry, I'm a little bit lost here. What do you mean by saying

> "but those values can be entered as the length in the YAML document anyway"?

I'm not sure if I understand it correctly. The 12-bit initial length is valid only when the format is DWARF64 (the prefix is 0xffffffff). When the prefix is in 0xfffffff0-0xfffffffe, the DWARF parser will not interpret the last 8-byte as length?

So we don't need LengthPrefix here, right? We can test the prefix in the preserved range by crafting something like

```
Format: DWARF32
Length: 0xfffffff0
```


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https://reviews.llvm.org/D81063