The compiler blows up processing the declaration of a tagged type
variable that has a C++ constructor without external or link name. After
this patch the frontend reports an error.

2019-07-22  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* freeze.adb (Freeze_Subprogram): Check that C++ constructors
	must have external or link name.

gcc/testsuite/

	* gnat.dg/cpp_constructor2.adb: New testcase.

From-SVN: r273670