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This is a follow-up patch for D148088 <https://reviews.llvm.org/D148088>. The
dynamic symbol index (`FileIndex::updatePreamble`) may run in a separate
thread, and the `DiagnosticConsumer` that is set up in `buildPreamble` might go
out of scope before it is used. This could result in a SIGSEGV when attempting
to call any method of the `DiagnosticConsumer` class.
The function `buildPreamble` sets up the `DiagnosticConsumer` as follows:
... buildPreamble(...) {
...
StoreDiags PreambleDiagnostics;
...
llvm::IntrusiveRefCntPtr<DiagnosticsEngine> PreambleDiagsEngine =
CompilerInstance::createDiagnostics(&CI.getDiagnosticOpts(),
&PreambleDiagnostics,
/*ShouldOwnClient=*/false);
...
// The call might use the diagnostic consumer in a separate thread
PreambleCallback(...)
...
}
`PreambleDiagnostics` might be out of scope for `buildPreamble` function when
we call it inside `PreambleCallback` in a separate thread.
The Fix
The fix involves replacing the client (DiagnosticConsumer) with an
`IgnoringDiagConsumer` instance, which will print messages to the clangd log.
Alternatively, we can replace `PreambleDiagnostics` with an object that is
owned by `DiagnosticsEngine`.
Note
There is no corresponding LIT/GTest for this issue, since there is a specific
race condition that is difficult to reproduce within a test framework.
Test Plan:
ninja check-clangd
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D159363
Files:
clang-tools-extra/clangd/Preamble.cpp
Index: clang-tools-extra/clangd/Preamble.cpp
===================================================================
--- clang-tools-extra/clangd/Preamble.cpp
+++ clang-tools-extra/clangd/Preamble.cpp
@@ -706,6 +706,11 @@
// While extending the life of FileMgr and VFS, StatCache should also be
// extended.
Ctx->setStatCache(Result->StatCache);
+ // We have to setup DiagnosticConsumer that will be alife
+ // while preamble callback is executed
+ Ctx->getASTContext().getDiagnostics().setClient(new IgnoringDiagConsumer,
+ true);
+
PreambleCallback(std::move(*Ctx), Result->Pragmas);
}
return Result;
Index: clang-tools-extra/clangd/Preamble.cpp
===================================================================
--- clang-tools-extra/clangd/Preamble.cpp
+++ clang-tools-extra/clangd/Preamble.cpp
@@ -706,6 +706,11 @@
// While extending the life of FileMgr and VFS, StatCache should also be
// extended.
Ctx->setStatCache(Result->StatCache);
+ // We have to setup DiagnosticConsumer that will be alife
+ // while preamble callback is executed
+ Ctx->getASTContext().getDiagnostics().setClient(new IgnoringDiagConsumer,
+ true);
+
PreambleCallback(std::move(*Ctx), Result->Pragmas);
}
return Result;
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