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Fix miscompilations for debugger because of resilience #78728

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Merged
merged 1 commit into from
Jan 23, 2025
Merged

Fix miscompilations for debugger because of resilience #78728

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8 changes: 8 additions & 0 deletions lib/IRGen/GenDecl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6010,6 +6010,14 @@ bool IRGenModule::hasResilientMetadata(ClassDecl *D,
return false;
}

// Because the debugger can extend non public types outside of their module,
// also check that "D" is *not* resilient from the module that contains
// "asViewedFromRootClass".
if (Context.LangOpts.DebuggerSupport && asViewedFromRootClass &&
!D->hasResilientMetadata(asViewedFromRootClass->getModuleContext(),
expansion))
return false;

return D->hasResilientMetadata(getSwiftModule(), expansion);
}

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10 changes: 9 additions & 1 deletion lib/IRGen/IRGenSIL.cpp
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Expand Up @@ -8380,9 +8380,17 @@ void IRGenSILFunction::visitClassMethodInst(swift::ClassMethodInst *i) {
SILDeclRef method = i->getMember().getOverriddenVTableEntry();
auto methodType = i->getType().castTo<SILFunctionType>();

AccessLevel methodAccess = method.getDecl()->getEffectiveAccess();
auto *classDecl = cast<ClassDecl>(method.getDecl()->getDeclContext());
bool shouldUseDispatchThunk = false;
if (IGM.hasResilientMetadata(classDecl, ResilienceExpansion::Maximal)) {
// Because typechecking for the debugger has more lax rules, check the access
// level of the getter to decide whether to use a dispatch thunk for the
// debugger.
bool shouldUseDispatchThunkIfInDebugger =
!classDecl->getASTContext().LangOpts.DebuggerSupport ||
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IGM.Context

methodAccess == AccessLevel::Public;
if (IGM.hasResilientMetadata(classDecl, ResilienceExpansion::Maximal) &&
shouldUseDispatchThunkIfInDebugger) {
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Can this be tested by compiling Swift code to IR and passing -debugger-support?

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I tried that but it's not enough. To look up private classes LLDB implements the DebuggerClient interface, without that we can't write a test that can extend a non-public type in a different module, to emulate LLDB's behavior.

shouldUseDispatchThunk = true;
} else if (IGM.getOptions().VirtualFunctionElimination) {
// For VFE, use a thunk if the target class is in another module. This
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