Limit the template instantiation depth to some user-configurable value
(default: 99). Beyond this limit, produce an error and consider the
current template instantiation a failure.

The stack we're building to track the instantiations will, eventually,
be used to produce instantiation backtraces from diagnostics within
template instantiation. However, we're not quite there yet.

This adds a new Clang driver option -ftemplate-depth=NNN, which should
eventually be generated from the GCC command-line operation
-ftemplate-depth-NNN (note the '-' rather than the '='!). I did not
make the driver changes to do this mapping.

llvm-svn: 66513
diff --git a/clang/test/SemaTemplate/instantiation-depth.cpp b/clang/test/SemaTemplate/instantiation-depth.cpp
new file mode 100644
index 0000000..3b8acf2
--- /dev/null
+++ b/clang/test/SemaTemplate/instantiation-depth.cpp
@@ -0,0 +1,8 @@
+// RUN: clang -fsyntax-only -ftemplate-depth=5 -verify %s
+
+template<typename T> struct X : X<T*> { }; // expected-error{{recursive template instantiation exceeded maximum depth of 5}} \
+// expected-note{{use -ftemplate-depth=N to increase recursive template instantiation depth}}
+
+void test() { 
+  (void)sizeof(X<int>);
+}