Detect recursive default argument definition

If definition of default function argument uses itself, clang crashed,
because corresponding function parameter is not associated with the default
argument yet. With this fix clang emits appropriate error message.

This change fixes PR28105.

Differential Revision: http://reviews.llvm.org/D21301

llvm-svn: 272623

3 files changed, 12 insertions, 0 deletions

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index a607690a14c..9992c779890 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3107,6 +3107,7 @@ def err_use_of_default_argument_to_function_declared_later : Error<
   "use of default argument to function %0 that is declared later in class %1">;
 def note_default_argument_declared_here : Note<
   "default argument declared here">;
+def err_recursive_default_argument : Error<"recursive evaluation of default argument">;
 
 def ext_param_promoted_not_compatible_with_prototype : ExtWarn<
   "%diff{promoted type $ of K&R function parameter is not compatible with the "
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index f766091e54e..f617db91510 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -4566,6 +4566,13 @@ ExprResult Sema::BuildCXXDefaultArgExpr(SourceLocation CallLoc,
     }
   }
 
+  // If the default argument expression is not set yet, we are building it now.
+  if (!Param->hasInit()) {
+    Diag(Param->getLocStart(), diag::err_recursive_default_argument) << FD;
+    Param->setInvalidDecl();
+    return ExprError();
+  }
+
   // If the default expression creates temporaries, we need to
   // push them to the current stack of expression temporaries so they'll
   // be properly destroyed.
diff --git a/clang/test/SemaCXX/default2.cpp b/clang/test/SemaCXX/default2.cpp
index c4d40b4280e..8f77f300572 100644
--- a/clang/test/SemaCXX/default2.cpp
+++ b/clang/test/SemaCXX/default2.cpp
@@ -128,3 +128,7 @@ S<1> s;
 
 template <int I1 = I2, int I2 = 1> struct T {};  // expected-error-re {{use of undeclared identifier 'I2'{{$}}}}
 T<0, 1> t;
+
+struct PR28105 {
+  PR28105 (int = 0, int = 0, PR28105 = 0);  // expected-error{{recursive evaluation of default argument}}
+};