diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
--- a/clang/include/clang/AST/Decl.h
+++ b/clang/include/clang/AST/Decl.h
@@ -921,11 +921,13 @@
     /// Whether this parameter is an ObjC method parameter or not.
     unsigned IsObjCMethodParam : 1;
 
+    enum { NumScopeDepthOrObjCQualsBits = 7 };
+
     /// If IsObjCMethodParam, a Decl::ObjCDeclQualifier.
     /// Otherwise, the number of function parameter scopes enclosing
     /// the function parameter scope in which this parameter was
     /// declared.
-    unsigned ScopeDepthOrObjCQuals : 7;
+    unsigned ScopeDepthOrObjCQuals : NumScopeDepthOrObjCQualsBits;
 
     /// The number of parameters preceding this parameter in the
     /// function parameter scope in which it was declared.
@@ -1650,6 +1652,10 @@
     return ParmVarDeclBits.ScopeDepthOrObjCQuals;
   }
 
+  static constexpr unsigned getMaxFunctionScopeDepth() {
+    return (1u << ParmVarDeclBitfields::NumScopeDepthOrObjCQualsBits) - 1;
+  }
+
   /// Returns the index of this parameter in its prototype or method scope.
   unsigned getFunctionScopeIndex() const {
     return getParameterIndex();
diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -325,6 +325,8 @@
 def err_argument_required_after_attribute : Error<
   "argument required after attribute">;
 def err_missing_param : Error<"expected parameter declarator">;
+def err_function_scope_depth_exceeded : Error<
+  "function scope depth exceeded maximum of %0">, DefaultFatal;
 def err_missing_comma_before_ellipsis : Error<
   "C requires a comma prior to the ellipsis in a variadic function type">;
 def err_unexpected_typedef_ident : Error<
diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -6566,6 +6566,19 @@
        ParsedAttributes &FirstArgAttrs,
        SmallVectorImpl<DeclaratorChunk::ParamInfo> &ParamInfo,
        SourceLocation &EllipsisLoc) {
+
+  // Avoid exceeding the maximum function scope depth.
+  // See https://bugs.llvm.org/show_bug.cgi?id=19607
+  // Note Sema::ActOnParamDeclarator calls ParmVarDecl::setScopeInfo with
+  // getFunctionPrototypeDepth() - 1.
+  if (getCurScope()->getFunctionPrototypeDepth() - 1 >
+      ParmVarDecl::getMaxFunctionScopeDepth()) {
+    Diag(Tok.getLocation(), diag::err_function_scope_depth_exceeded)
+        << ParmVarDecl::getMaxFunctionScopeDepth();
+    cutOffParsing();
+    return;
+  }
+
   do {
     // FIXME: Issue a diagnostic if we parsed an attribute-specifier-seq
     // before deciding this was a parameter-declaration-clause.
diff --git a/clang/test/Parser/nested_blocks_overflow.cpp b/clang/test/Parser/nested_blocks_overflow.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Parser/nested_blocks_overflow.cpp
@@ -0,0 +1,54 @@
+// RUN: %clang %s -fsyntax-only -fblocks -fbracket-depth=512
+// RUN: not %clang %s -fsyntax-only -fblocks -fbracket-depth=512 -DFAIL 2>&1 | FileCheck %s
+
+template <class T> int foo(T &&t);
+
+void bar(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+
+^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(^(int x = foo(
+
+#ifdef FAIL
+^(int x = foo(
+#endif
+
+^(int x = foo(1)){}
+
+#ifdef FAIL
+)){}
+#endif
+
+)){})){})){})){})){})){}
+
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+));
+
+// CHECK: fatal error: function scope depth exceeded maximum of 127
diff --git a/clang/test/Parser/nested_function_prototype_overflow.cpp b/clang/test/Parser/nested_function_prototype_overflow.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Parser/nested_function_prototype_overflow.cpp
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 %s -fsyntax-only
+// RUN: not %clang_cc1 %s -fsyntax-only -DFAIL 2>&1 | FileCheck %s
+
+void foo(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(void (*f)(
+#ifdef FAIL
+void (*f)()
+#endif
+)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))));
+// CHECK: fatal error: function scope depth exceeded maximum of 127
diff --git a/clang/test/Parser/nested_lambda_overflow.cpp b/clang/test/Parser/nested_lambda_overflow.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/Parser/nested_lambda_overflow.cpp
@@ -0,0 +1,55 @@
+// RUN: %clang %s -fsyntax-only -fbracket-depth=512
+// RUN: not %clang %s -fsyntax-only -fbracket-depth=512 -DFAIL 2>&1 | FileCheck %s
+
+template <class T> int foo(T &&t);
+
+void bar(int x = foo(
+
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+
+[](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo([](int x = foo(
+
+#ifdef FAIL
+[](int x = foo(
+#endif
+
+[](int x = foo(1)){}
+
+#ifdef FAIL
+)){}
+#endif
+
+)){})){})){})){})){})){}
+
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+)){})){})){})){})){})){})){})){}
+));
+
+// CHECK: fatal error: function scope depth exceeded maximum of 127