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[C++ PATCH] Fix -Wimplicit-fallthrough in templates (PR c++/77886)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Jason Merrill <jason at redhat dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Sat, 8 Oct 2016 08:13:50 +0200
- Subject: [C++ PATCH] Fix -Wimplicit-fallthrough in templates (PR c++/77886)
- Authentication-results: sourceware.org; auth=none
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
As the testcase shows, we weren't copying over FALLTHROUGH_LABEL_P during
instantiations, which means that // FALLTHROUGH comments in templates were
ignored (while [[fallthrough]];, being represented as internal calls,
worked fine).
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?
2016-10-08 Jakub Jelinek <jakub@redhat.com>
PR c++/77886
* pt.c (tsubst_expr) <case CASE_LABEL_EXPR> Copy over
FALLTHROUGH_LABEL_P flag to the new LABEL_DECL.
(tsubst_expr) <case LABEL_EXPR>: Likewise.
* g++.dg/warn/Wimplicit-fallthrough-2.C: New test.
--- gcc/cp/pt.c.jj 2016-10-07 21:36:47.000000000 +0200
+++ gcc/cp/pt.c 2016-10-07 23:51:53.244510627 +0200
@@ -15456,7 +15456,10 @@ tsubst_expr (tree t, tree args, tsubst_f
{
tree low = RECUR (CASE_LOW (t));
tree high = RECUR (CASE_HIGH (t));
- finish_case_label (EXPR_LOCATION (t), low, high);
+ tree l = finish_case_label (EXPR_LOCATION (t), low, high);
+ if (l && TREE_CODE (l) == CASE_LABEL_EXPR)
+ FALLTHROUGH_LABEL_P (CASE_LABEL (l))
+ = FALLTHROUGH_LABEL_P (CASE_LABEL (t));
}
break;
@@ -15466,6 +15469,8 @@ tsubst_expr (tree t, tree args, tsubst_f
tree label;
label = finish_label_stmt (DECL_NAME (decl));
+ if (TREE_CODE (label) == LABEL_DECL)
+ FALLTHROUGH_LABEL_P (label) = FALLTHROUGH_LABEL_P (decl);
if (DECL_ATTRIBUTES (decl) != NULL_TREE)
cplus_decl_attributes (&label, DECL_ATTRIBUTES (decl), 0);
}
--- gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-2.C.jj 2016-10-07 23:59:03.851102742 +0200
+++ gcc/testsuite/g++.dg/warn/Wimplicit-fallthrough-2.C 2016-10-08 00:04:25.759058055 +0200
@@ -0,0 +1,66 @@
+// PR c++/77886
+// { dg-do compile }
+// { dg-options "-Wimplicit-fallthrough" }
+
+template <int N>
+int
+foo (int x, int y)
+{
+ switch (x)
+ {
+ case 1:
+ x++; // { dg-bogus "this statement may f\[ahlotu\]*gh" }
+ // FALLTHROUGH
+ case 2:
+ x++;
+ break;
+ case 3:
+ x++; // { dg-bogus "this statement may f\[ahlotu\]*gh" }
+ // FALLTHROUGH
+ lab:
+ case 4:
+ x++;
+ break;
+ case 5:
+ x++; // { dg-bogus "this statement may f\[ahlotu\]*gh" }
+ // FALLTHROUGH
+ default:
+ x++;
+ break;
+ case 26:
+ goto lab;
+ }
+#if __cplusplus >= 201103L
+ switch (y)
+ {
+ case 1:
+ y++; // { dg-bogus "this statement may f\[ahlotu\]*gh" }
+ [[fallthrough]];
+ case 2:
+ y++;
+ break;
+ case 3:
+ y++; // { dg-bogus "this statement may f\[ahlotu\]*gh" }
+ [[fallthrough]];
+ lab2:
+ case 4:
+ y++;
+ break;
+ case 5:
+ y++; // { dg-bogus "this statement may f\[ahlotu\]*gh" }
+ [[fallthrough]];
+ default:
+ y++;
+ break;
+ case 26:
+ goto lab2;
+ }
+#endif
+ return x + y;
+}
+
+int
+bar (int x, int y)
+{
+ return foo<0> (x, y);
+}
Jakub