[ubsan] Improve diagnostics for return value checks (clang)
This patch makes ubsan's nonnull return value diagnostics more precise,
which makes the diagnostics more useful when there are multiple return
statements in a function. Example:
1 |__attribute__((returns_nonnull)) char *foo() {
2 | if (...) {
3 | return expr_which_might_evaluate_to_null();
4 | } else {
5 | return another_expr_which_might_evaluate_to_null();
6 | }
7 |} // <- The current diagnostic always points here!
runtime error: Null returned from Line 7, Column 2!
With this patch, the diagnostic would point to either Line 3, Column 5
or Line 5, Column 5.
This is done by emitting source location metadata for each return
statement in a sanitized function. The runtime is passed a pointer to
the appropriate metadata so that it can prepare and deduplicate reports.
Compiler-rt patch (with more tests): https://reviews.llvm.org/D34298
Differential Revision: https://reviews.llvm.org/D34299
llvm-svn: 306163
diff --git a/clang/lib/CodeGen/CGStmt.cpp b/clang/lib/CodeGen/CGStmt.cpp
index 683f366..a13c386 100644
--- a/clang/lib/CodeGen/CGStmt.cpp
+++ b/clang/lib/CodeGen/CGStmt.cpp
@@ -1024,6 +1024,18 @@
/// if the function returns void, or may be missing one if the function returns
/// non-void. Fun stuff :).
void CodeGenFunction::EmitReturnStmt(const ReturnStmt &S) {
+ if (requiresReturnValueCheck()) {
+ llvm::Constant *SLoc = EmitCheckSourceLocation(S.getLocStart());
+ auto *SLocPtr =
+ new llvm::GlobalVariable(CGM.getModule(), SLoc->getType(), false,
+ llvm::GlobalVariable::PrivateLinkage, SLoc);
+ SLocPtr->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
+ CGM.getSanitizerMetadata()->disableSanitizerForGlobal(SLocPtr);
+ assert(ReturnLocation.isValid() && "No valid return location");
+ Builder.CreateStore(Builder.CreateBitCast(SLocPtr, Int8PtrTy),
+ ReturnLocation);
+ }
+
// Returning from an outlined SEH helper is UB, and we already warn on it.
if (IsOutlinedSEHHelper) {
Builder.CreateUnreachable();