https://gcc.gnu.org/g:d9318caed3bbff8136d13e00dcfc020a59d10f78
commit r15-329-gd9318caed3bbff8136d13e00dcfc020a59d10f78
Author: Marek Polacek <pola...@redhat.com>
Date: Wed Jan 24 18:06:48 2024 -0500
c++: #pragma doesn't disable -Wunused-label [PR113582]
The PR complains that
void do_something(){
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-label"
start:;
#pragma GCC diagnostic pop
} #1
doesn't work. That's because we warn_for_unused_label only while we're
in finish_function, meaning we're at #1 where we're outside the #pragma
region. We can use suppress_warning + warning_suppressed_p to fix this.
Note that I'm not using TREE_USED. Propagating it in tsubst_stmt/LABEL_EXPR
from decl to label would mean that we don't warn in do_something2, but
I think we want the warning there: we're in a template and the goto is
a discarded statement.
PR c++/113582
gcc/c-family/ChangeLog:
* c-warn.cc (warn_for_unused_label): Don't warn if -Wunused-label
has
been suppressed for the label.
gcc/cp/ChangeLog:
* parser.cc (cp_parser_label_for_labeled_statement):
suppress_warning
if it's not enabled at input_location.
* pt.cc (tsubst_stmt): Call copy_warning.
gcc/testsuite/ChangeLog:
* g++.dg/warn/Wunused-label-4.C: New test.
Diff:
---
gcc/c-family/c-warn.cc | 4 +++-
gcc/cp/parser.cc | 6 +++++-
gcc/cp/pt.cc | 9 +++++----
gcc/testsuite/g++.dg/warn/Wunused-label-4.C | 29 +++++++++++++++++++++++++++++
4 files changed, 42 insertions(+), 6 deletions(-)
diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
index bff87be05ae3..5b2d6805c790 100644
--- a/gcc/c-family/c-warn.cc
+++ b/gcc/c-family/c-warn.cc
@@ -2185,7 +2185,9 @@ warn_for_unused_label (tree label)
{
if (!TREE_USED (label))
{
- if (DECL_INITIAL (label))
+ if (warning_suppressed_p (label, OPT_Wunused_label))
+ /* Don't warn. */;
+ else if (DECL_INITIAL (label))
warning (OPT_Wunused_label, "label %q+D defined but not used", label);
else
warning (OPT_Wunused_label, "label %q+D declared but not defined",
label);
diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index c4191200291d..7306ce9a8a8b 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -13108,7 +13108,11 @@ cp_parser_label_for_labeled_statement (cp_parser*
parser, tree attributes)
/* Anything else must be an ordinary label. */
label = finish_label_stmt (cp_parser_identifier (parser));
if (label && TREE_CODE (label) == LABEL_DECL)
- FALLTHROUGH_LABEL_P (label) = fallthrough_p;
+ {
+ FALLTHROUGH_LABEL_P (label) = fallthrough_p;
+ if (!warning_enabled_at (input_location, OPT_Wunused_label))
+ suppress_warning (label, OPT_Wunused_label);
+ }
break;
}
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 1816bfd1f401..8787eabb9fdb 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -18837,11 +18837,12 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t
complain, tree in_decl)
case LABEL_EXPR:
{
tree decl = LABEL_EXPR_LABEL (t);
- tree label;
-
- label = finish_label_stmt (DECL_NAME (decl));
+ tree label = finish_label_stmt (DECL_NAME (decl));
if (TREE_CODE (label) == LABEL_DECL)
- FALLTHROUGH_LABEL_P (label) = FALLTHROUGH_LABEL_P (decl);
+ {
+ FALLTHROUGH_LABEL_P (label) = FALLTHROUGH_LABEL_P (decl);
+ copy_warning (label, decl);
+ }
if (DECL_ATTRIBUTES (decl) != NULL_TREE)
cplus_decl_attributes (&label, DECL_ATTRIBUTES (decl), 0);
}
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-label-4.C
b/gcc/testsuite/g++.dg/warn/Wunused-label-4.C
new file mode 100644
index 000000000000..d194f043d215
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-label-4.C
@@ -0,0 +1,29 @@
+// PR c++/113582
+// { dg-do compile { target c++17 } }
+// { dg-options "-Wunused-label" }
+
+template<bool B> void
+do_something ()
+{
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-label"
+start:
+ if constexpr(B)
+ goto start;
+#pragma GCC diagnostic pop
+}
+
+template<bool B> void
+do_something2 ()
+{
+start: // { dg-warning "defined but not used" }
+ if constexpr(B)
+ goto start;
+}
+
+void
+g ()
+{
+ do_something<0>();
+ do_something2<0>();
+}
