[Lldb-commits] [PATCH] D128268: [lldb] Fix reading i686-windows executables with GNU environment

Tue Jun 21 07:32:22 PDT 2022

mstorsjo added a comment.

In D128268#3598967 <https://reviews.llvm.org/D128268#3598967>, @DavidSpickett wrote:

>> However, after this commit, if the object file is advertised with the different environment (either when built in a mingw environment, or if that setting is set), the fat binary validation won't accept the file any longer.
>
> Is "this commit" referring to https://reviews.llvm.org/rG25c8a061c5739677d2fc0af29a8cc9520207b923 or to the change we're reviewing here?

Sorry, I meant 25c8a061c5739677d2fc0af29a8cc9520207b923 <https://reviews.llvm.org/rG25c8a061c5739677d2fc0af29a8cc9520207b923>.

> I'm struggling to think through what this is actually fixing. Is the issue that one half of a fat binary can have a different ABI? Wouldn't both sides of the fat binary be loaded as the ABI chosen in the setting, or is that exactly what you're fixing.

The issue is that in the case of a fat binary, we run a loop to check and pick an architecture out of it: https://github.com/llvm/llvm-project/blob/main/lldb/source/Target/TargetList.cpp#L173-L184 This is checked against the architectures added here: https://github.com/llvm/llvm-project/blob/main/lldb/source/Plugins/Platform/Windows/PlatformWindows.cpp#L127-L131

(In the case of a non-fat binary, i.e. all other architectures than i386/i686 on PECOFF, we hit this case here, where we don't validate the arch spec at all: https://github.com/llvm/llvm-project/blob/main/lldb/source/Target/TargetList.cpp#L160-L164)

Now since the addition of the new setting in 25c8a061c5739677d2fc0af29a8cc9520207b923 <https://reviews.llvm.org/rG25c8a061c5739677d2fc0af29a8cc9520207b923>, `ObjectFile::GetModuleSpecifications` can return `i386-pc-windows-gnu` and `i686-pc-windows-gnu`, while `PlatformWindows` provides a list containing `i386-pc-windows` (which is normalized to `i386-pc-windows-msvc`) and `i686-pc-windows` (`...-msvc`). Due to the differing environments, these are deemed incompatible, and LLDB flat out refuses to load the file, with the error message `error: no matching platforms found for this file`.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D128268/new/

https://reviews.llvm.org/D128268