On 1/25/24 20:38, Marek Polacek wrote:
Low prio and not a regression. Feel free to ignore till GCC 15.
OK for stage 1.
Bootstrapped/regtested on x86_64-pc-linux-gnu. -- >8 -- 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. --- 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(-) create mode 100644 gcc/testsuite/g++.dg/warn/Wunused-label-4.C diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc index 8168696fa45..fdb5338f6f6 100644 --- a/gcc/c-family/c-warn.cc +++ b/gcc/c-family/c-warn.cc @@ -2186,7 +2186,9 @@ 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 3748ccd49ff..224d47f2f90 100644 --- a/gcc/cp/parser.cc +++ b/gcc/cp/parser.cc @@ -13093,7 +13093,11 @@ 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.ccindex 74013533b0f..af9fd8f6f03 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -18796,11 +18796,12 @@ 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 00000000000..d194f043d21 --- /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>(); +} base-commit: f22a7ae8a96f7e5e330b12bd5045424619aa4926
