[PATCH] D25213: Fix PR28181: Prevent operator overloading related assertion failure crash that happens in C only

[Alex Lorenz via cfe-commits]

arphaman created this revision.
arphaman added reviewers: rsmith, rjmccall.
arphaman added a subscriber: cfe-commits.
arphaman set the repository for this revision to rL LLVM.

This patch fixes a crash that happens because of an assertion failure in C mode only. The assertion failure happens because of a cast to a C++ record decl in code that assumes (correctly, AFAIK) that overloaded operator handling is used in C++ mode only.

This patch approaches this problem in the following manner: when clang isn't in C++ mode, it exits early from the method 'Sema::CreateOverloadedBinOp'. The operator handling is performed using the 'Sema::CreateBuiltinBinOp' method when exiting the previously mentioned method. I think that this approach works because, AFAIK, clang doesn't support operator overloading without LangOpts.CPlusPlus, so it doesn't need to handle the overloading in the same way, and redirecting to builtin operator handling deals with the C operators correctly. I also tried other approaches and strategies but they didn't seem to work as well as this one.

I'm not familiar with all the intricacies of Sema, and I realize that this might be the wrong approach for this problem. Please let me know if this a sound strategy or not.

This bug is a regression since r236337.


Repository:
  rL LLVM

https://reviews.llvm.org/D25213

Files:
  lib/Sema/SemaOverload.cpp
  test/Sema/PR28181.c


Index: test/Sema/PR28181.c
===================================================================
--- /dev/null
+++ test/Sema/PR28181.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+struct spinlock_t {
+  int lock;
+} audit_skb_queue;
+
+void fn1() {
+  audit_skb_queue = (lock); // expected-error {{use of undeclared identifier 'lock'; did you mean 'long'?}}
+}                           // expected-error at -1 {{assigning to 'struct spinlock_t' from incompatible type '<overloaded function type>'}}
+
+void fn2() {
+  audit_skb_queue + (lock); // expected-error {{use of undeclared identifier 'lock'; did you mean 'long'?}}
+}                           // expected-error at -1 {{reference to overloaded function could not be resolved; did you mean to call it?}}
Index: lib/Sema/SemaOverload.cpp
===================================================================
--- lib/Sema/SemaOverload.cpp
+++ lib/Sema/SemaOverload.cpp
@@ -11804,7 +11804,8 @@
   // various built-in candidates, but as DR507 points out, this can lead to
   // problems. So we do it this way, which pretty much follows what GCC does.
   // Note that we go the traditional code path for compound assignment forms.
-  if (Opc == BO_Assign && !Args[0]->getType()->isOverloadableType())
+  if (!LangOpts.CPlusPlus ||
+      (Opc == BO_Assign && !Args[0]->getType()->isOverloadableType()))
     return CreateBuiltinBinOp(OpLoc, Opc, Args[0], Args[1]);
 
   // If this is the .* operator, which is not overloadable, just


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