Re: [PATCH, C++] Warn on redefinition of builtin functions (PR c++/71973)

[Jason Merrill]

On 11/05/2016 12:44 PM, Bernd Edlinger wrote:
+             warning_at (DECL_SOURCE_LOCATION (newdecl), 0,
+                         "declaration of %q+#D conflicts with built-in "
+                         "declaration %q#D", newdecl, olddecl);

There needs to be a way to disable this warning, even if it's enabled by 
default.

-      TREE_NOTHROW (olddecl) = 0;
+      TREE_NOTHROW (olddecl) = TREE_NOTHROW (newdecl);

I still think a better fix would be to add a copy of TREE_NOTHROW to the 
else block of the if (types_match), to go with the existing copies of 
TREE_READONLY and TREE_THIS_VOLATILE.

Jason