[all-commits] [llvm/llvm-project] da293b: [lldb][HostInfoMacOSX] Try to use DW_AT_LLVM_sysro...

[Michael Buch via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: da293b850be3fc5b2047769f55823e41b07625c9
      https://github.com/llvm/llvm-project/commit/da293b850be3fc5b2047769f55823e41b07625c9
  Author: Michael Buch <michaelbuch12 at gmail.com>
  Date:   2025-03-03 (Mon, 03 Mar 2025)

  Changed paths:
    M lldb/include/lldb/Host/macosx/HostInfoMacOSX.h
    M lldb/include/lldb/Utility/XcodeSDK.h
    M lldb/source/Plugins/Platform/MacOSX/PlatformDarwin.cpp
    M lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
    M lldb/source/Utility/XcodeSDK.cpp
    M lldb/unittests/SymbolFile/DWARF/XcodeSDKModuleTests.cpp
    M lldb/unittests/Utility/XcodeSDKTest.cpp

  Log Message:
  -----------
  [lldb][HostInfoMacOSX] Try to use DW_AT_LLVM_sysroot instead of xcrun when looking up SDK (#128712)

`GetSDKRoot` uses `xcrun` to find an SDK root path for a given SDK
version string. But if the SDK doesn't exist in the Xcode installations,
but instead lives in the `CommandLineTools`, `xcrun` will fail to find
it. Negative searches for an SDK path cost a lot (a few seconds) each
time `xcrun` is invoked. We do cache negative results in
`find_cached_path` inside LLDB, but we would still pay the price on
every new debug session the first time we evaluate an expression. This
doesn't only cause a noticable delay in running the expression, but also
generates following error:
```
error: Error while searching for Xcode SDK: timed out waiting for shell command to complete
(int) $0 = 42
```

In this patch we avoid these possibly expensive calls to `xcrun` by
checking the `DW_AT_LLVM_sysroot`, and if it exists, using that as the
SDK path. We need an explicit check for the `CommandLineTools` path
before we call `RegisterXcodeSDK`, because that will try to call
`xcrun`. This won't prevent other uses of `GetSDKRoot` popping up that
cause us to make expensive `xcrun` calls, but for now this addresses the
regression in the expression evaluator. We also had to adjust the
`XcodeSDK::Merge` logic to update the sysroot. There is one case for
which this wouldn't make sense: if a CU was compiled with
`CommandLineTools` and a different one with an older internal SDK, in
that case we would update the `CommandLineTools` sysroot with a
`.Internal.sdk` prefix, which won't possibly exist for
`CommandLineTools`. I added a unit-test for this. Not sure if we want to
explicitly detect and disallow this, given it's quite a niche scenario.

rdar://113619904
rdar://113619723



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications