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[clang-repl] Keep the first llvm::Module empty to avoid invalid memory access. #89031

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Merged
merged 1 commit into from
Apr 20, 2024
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[clang-repl] Keep the first llvm::Module empty to avoid invalid memory access. #89031

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25 changes: 20 additions & 5 deletions clang/lib/Interpreter/IncrementalParser.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -209,6 +209,10 @@ IncrementalParser::IncrementalParser(Interpreter &Interp,
if (Err)
return;
CI->ExecuteAction(*Act);

if (getCodeGen())
CachedInCodeGenModule = std::move(GenModule());

std::unique_ptr<ASTConsumer> IncrConsumer =
std::make_unique<IncrementalASTConsumer>(Interp, CI->takeASTConsumer());
CI->setASTConsumer(std::move(IncrConsumer));
Expand All @@ -224,11 +228,8 @@ IncrementalParser::IncrementalParser(Interpreter &Interp,
return; // PTU.takeError();
}

if (CodeGenerator *CG = getCodeGen()) {
std::unique_ptr<llvm::Module> M(CG->ReleaseModule());
CG->StartModule("incr_module_" + std::to_string(PTUs.size()),
M->getContext());
PTU->TheModule = std::move(M);
if (getCodeGen()) {
PTU->TheModule = std::move(GenModule());
Comment on lines +231 to +232
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Just to confirm my understanding of the change: this is an independent deduplication cleanup, right?

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Yes, independent clean up.

assert(PTU->TheModule && "Failed to create initial PTU");
}
}
Expand Down Expand Up @@ -364,6 +365,20 @@ IncrementalParser::Parse(llvm::StringRef input) {
std::unique_ptr<llvm::Module> IncrementalParser::GenModule() {
static unsigned ID = 0;
if (CodeGenerator *CG = getCodeGen()) {
// Clang's CodeGen is designed to work with a single llvm::Module. In many
// cases for convenience various CodeGen parts have a reference to the
// llvm::Module (TheModule or Module) which does not change when a new
// module is pushed. However, the execution engine wants to take ownership
// of the module which does not map well to CodeGen's design. To work this
// around we created an empty module to make CodeGen happy. We should make
// sure it always stays empty.
assert((!CachedInCodeGenModule ||
(CachedInCodeGenModule->empty() &&
CachedInCodeGenModule->global_empty() &&
CachedInCodeGenModule->alias_empty() &&
CachedInCodeGenModule->ifunc_empty() &&
CachedInCodeGenModule->named_metadata_empty())) &&
"CodeGen wrote to a readonly module");
std::unique_ptr<llvm::Module> M(CG->ReleaseModule());
CG->StartModule("incr_module_" + std::to_string(ID++), M->getContext());
return M;
Expand Down
5 changes: 5 additions & 0 deletions clang/lib/Interpreter/IncrementalParser.h
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#include <memory>
namespace llvm {
class LLVMContext;
class Module;
} // namespace llvm

namespace clang {
Expand Down Expand Up @@ -57,6 +58,10 @@ class IncrementalParser {
/// of code.
std::list<PartialTranslationUnit> PTUs;

/// When CodeGen is created the first llvm::Module gets cached in many places
/// and we must keep it alive.
std::unique_ptr<llvm::Module> CachedInCodeGenModule;

IncrementalParser();

public:
Expand Down
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