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Re: [C++ PATCH] PR c++/79133

On 08/07/2018 07:12 AM, Ville Voutilainen wrote:
On 8 July 2018 at 02:08, Ville Voutilainen <> wrote:
On 8 July 2018 at 01:54, Paolo Carlini <> wrote:
That would make this more consistent with such a shadow warning, but I
don't want
to use the shadowing wording (which would be easy to do; just set
'shadowed' and do
a 'goto inform'), because this isn't shadowing in the precise sense;
the shadowing cases
are warnings, whereas this is more like the redeclaration errors in
the same function.

... indeed and that annoys me a bit. Not having studied at all c++/79133 so
far (sorry) it seems a little weird to me that according to the standard we
have to handle the two types of "shadowing" in different ways, one more
strict, one less. Thus I would suggest double checking the details of that,
eventually with Jason too in terms of the actual patch you would like to

Well. The PR is about DR 2211 which, in simple terms, says that lambda
and captures cannot have the same name. See

That's stricter than -Wshadow, but otherwise equally strict as the
other error cases already handled
in check_local_shadow. So I'll make this error case more consistent
with the others. We already
handle redeclaration errors slightly differently from shadowing
warnings in that function.

Here's an updated patch. Tested on Linux-PPC64, OK for trunk?


2018-08-06  Ville Voutilainen  <>


     PR c++/79133
     * name-lookup.c (check_local_shadow): Reject captures and parameters
     with the same name.

       if (DECL_CONTEXT (old) == current_function_decl
 	  && TREE_CODE (decl) != PARM_DECL
-	  && TREE_CODE (old) == PARM_DECL)
+	  && TREE_CODE (old) == PARM_DECL
+	  && !is_capture_proxy (decl))
 	  /* Go to where the parms should be and see if we find
 	     them there.  */
@@ -2665,6 +2667,21 @@ check_local_shadow (tree decl)
+      /* DR 2211: check that captures and parameters
+	 do not have the same name. */
+      else if (is_capture_proxy (decl))

Maybe put this block first rather than add !is_capture_proxy to the if condition?


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