Re: [C++ Patch] PR 68374 ("G++ -Wshadow doesn't warn about static member shadowing")

[Paolo Carlini]

Hi,

On 23/04/2018 23:43, Jason Merrill wrote:
On Mon, Apr 23, 2018 at 5:17 PM, Paolo Carlini <paolo.carl...@oracle.com> wrote:
Hi,
this issue is by and large fixed in trunk, thus I wanted to resolve it as
such, marking it as fixed for 8.1.0. However the text of the warning is
misleading / wrong:

     declaration of ‘mVar’ shadows a previous local

where in fact the shadowed declaration isn't local, is a static data member
of the class. It seems to me that we should simply not handle such static
old decls in the conditional block handling locals shadowing other locals,
thus handle those below, together with other non-static member declarations.
Tested x86-64-linux.
!TREE_STATIC seems like the wrong test here; that's also true for
static local variables.

Maybe check DECL_FUNCTION_SCOPE_P instead?
Indeed. I don't know how I mis-analyzed that block to conclude that 
previous static locals weren't handled at all there.

Anyway, I added a testcase for that and I'm running again the full 
testsuite (g++.dg is Ok). Ok if it passes?

Thanks!
Paolo.

//////////////////////
Index: cp/name-lookup.c
===================================================================
--- cp/name-lookup.c    (revision 259571)
+++ cp/name-lookup.c    (working copy)
@@ -2638,6 +2638,7 @@ check_local_shadow (tree decl)
          || (TREE_CODE (old) == TYPE_DECL
              && (!DECL_ARTIFICIAL (old)
                  || TREE_CODE (decl) == TYPE_DECL)))
+      && DECL_FUNCTION_SCOPE_P (old)
       && (!DECL_ARTIFICIAL (decl)
          || DECL_IMPLICIT_TYPEDEF_P (decl)
          || (VAR_P (decl) && DECL_ANON_UNION_VAR_P (decl))))
Index: testsuite/g++.dg/warn/Wshadow-13.C
===================================================================
--- testsuite/g++.dg/warn/Wshadow-13.C  (nonexistent)
+++ testsuite/g++.dg/warn/Wshadow-13.C  (working copy)
@@ -0,0 +1,8 @@
+// PR c++/68374
+// { dg-options "-Wshadow" }
+
+class f {
+  static int mVar;  // { dg-message "shadowed declaration" }
+  int g(int x) { int mVar=3; return x+mVar; }  // { dg-warning "shadows a 
member of 'f'" }
+};
+int f::mVar = 1;
Index: testsuite/g++.dg/warn/Wshadow-14.C
===================================================================
--- testsuite/g++.dg/warn/Wshadow-14.C  (nonexistent)
+++ testsuite/g++.dg/warn/Wshadow-14.C  (working copy)
@@ -0,0 +1,10 @@
+// PR c++/68374
+// { dg-options "-Wshadow" }
+
+void foo ()
+{
+  static int i;  // { dg-message "shadowed declaration" }
+  {
+    int i;  // { dg-warning "shadows a previous local" }
+  }
+}