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Re: [C++ PATCH] Avoid -Wreturn-type warnings if a switch has default label, no breaks inside of it, but is followed by a break (PR sanitizer/81275)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Jason Merrill <jason at redhat dot com>, Nathan Sidwell <nathan at acm dot org>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Sun, 26 Nov 2017 01:22:56 +0100
- Subject: Re: [C++ PATCH] Avoid -Wreturn-type warnings if a switch has default label, no breaks inside of it, but is followed by a break (PR sanitizer/81275)
- Authentication-results: sourceware.org; auth=none
- References: <20171124215953.GE14653@tucnak> <20171125090122.GH14653@tucnak>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Sat, Nov 25, 2017 at 10:01:22AM +0100, Jakub Jelinek wrote:
> Actually, thinking about it some more, maybe it would be more efficient
> to gather this information during construction of the SWITCH_STMT in some
> new flag on the tree, so cxx_block_may_fallthru would just:
Here it is implemented, bootstrapped/regtested on x86_64-linux and
i686-linux, ok for trunk?
2017-11-25 Jakub Jelinek <jakub@redhat.com>
PR sanitizer/81275
* cp-tree.h (SWITCH_STMT_CANNOT_FALLTHRU_P): Define.
(note_break_stmt, note_iteration_stmt_body_start,
note_iteration_stmt_body_end): Declare.
* decl.c (struct cp_switch): Add has_default_p, break_stmt_seen_p
and in_loop_body_p fields.
(push_switch): Clear them.
(pop_switch): Set SWITCH_STMT_CANNOT_FALLTHRU_P if has_default_p
and !break_stmt_seen_p. Assert in_loop_body_p is false.
(note_break_stmt, note_iteration_stmt_body_start,
note_iteration_stmt_body_end): New functions.
(finish_case_label): Set has_default_p when both low and high
are NULL_TREE.
* parser.c (cp_parser_iteration_statement): Use
note_iteration_stmt_body_start and note_iteration_stmt_body_end
around parsing iteration body.
* pt.c (tsubst_expr): Likewise.
* cp-objcp-common.c (cxx_block_may_fallthru): Return false for
SWITCH_STMT which contains no BREAK_STMTs, contains a default:
CASE_LABEL_EXPR and where SWITCH_STMT_BODY isn't empty and
can't fallthru.
* semantics.c (finish_break_stmt): Call note_break_stmt.
* g++.dg/warn/pr81275-1.C: New test.
* g++.dg/warn/pr81275-2.C: New test.
* g++.dg/warn/pr81275-3.C: New test.
--- gcc/cp/cp-tree.h.jj 2017-11-17 08:40:32.000000000 +0100
+++ gcc/cp/cp-tree.h 2017-11-25 21:25:48.277897180 +0100
@@ -364,6 +364,7 @@ extern GTY(()) tree cp_global_trees[CPTI
IF_STMT_CONSTEXPR_P (IF_STMT)
TEMPLATE_TYPE_PARM_FOR_CLASS (TEMPLATE_TYPE_PARM)
DECL_NAMESPACE_INLINE_P (in NAMESPACE_DECL)
+ SWITCH_STMT_CANNOT_FALLTHRU_P (in SWITCH_STMT)
1: IDENTIFIER_KIND_BIT_1 (in IDENTIFIER_NODE)
TI_PENDING_TEMPLATE_FLAG.
TEMPLATE_PARMS_FOR_INLINE.
@@ -4840,6 +4841,12 @@ more_aggr_init_expr_args_p (const aggr_i
#define SWITCH_STMT_BODY(NODE) TREE_OPERAND (SWITCH_STMT_CHECK (NODE), 1)
#define SWITCH_STMT_TYPE(NODE) TREE_OPERAND (SWITCH_STMT_CHECK (NODE), 2)
#define SWITCH_STMT_SCOPE(NODE) TREE_OPERAND (SWITCH_STMT_CHECK (NODE), 3)
+/* Set if the body of a switch stmt contains a default: case label
+ and does not contain any break; stmts, thus if SWITCH_STMT_BODY
+ is not empty and doesn't fallthru, then the whole SWITCH_STMT
+ can't fallthru either. */
+#define SWITCH_STMT_CANNOT_FALLTHRU_P(NODE) \
+ TREE_LANG_FLAG_0 (SWITCH_STMT_CHECK (NODE))
/* STMT_EXPR accessor. */
#define STMT_EXPR_STMT(NODE) TREE_OPERAND (STMT_EXPR_CHECK (NODE), 0)
@@ -6102,6 +6109,9 @@ enum cp_tree_node_structure_enum cp_tree
extern void finish_scope (void);
extern void push_switch (tree);
extern void pop_switch (void);
+extern void note_break_stmt (void);
+extern bool note_iteration_stmt_body_start (void);
+extern void note_iteration_stmt_body_end (bool);
extern tree make_lambda_name (void);
extern int decls_match (tree, tree);
extern bool maybe_version_functions (tree, tree);
--- gcc/cp/decl.c.jj 2017-11-22 21:37:46.000000000 +0100
+++ gcc/cp/decl.c 2017-11-25 21:25:26.306162437 +0100
@@ -3427,6 +3427,13 @@ struct cp_switch
/* Remember whether there was a case value that is outside the
range of the original type of the controlling expression. */
bool outside_range_p;
+ /* Remember whether a default: case label has been seen. */
+ bool has_default_p;
+ /* Remember whether a BREAK_STMT has been seen in this SWITCH_STMT. */
+ bool break_stmt_seen_p;
+ /* Set if inside of {FOR,DO,WHILE}_BODY nested inside of a switch,
+ where BREAK_STMT doesn't belong to the SWITCH_STMT. */
+ bool in_loop_body_p;
};
/* A stack of the currently active switch statements. The innermost
@@ -3449,6 +3456,9 @@ push_switch (tree switch_stmt)
p->switch_stmt = switch_stmt;
p->cases = splay_tree_new (case_compare, NULL, NULL);
p->outside_range_p = false;
+ p->has_default_p = false;
+ p->break_stmt_seen_p = false;
+ p->in_loop_body_p = false;
switch_stack = p;
}
@@ -3469,11 +3479,50 @@ pop_switch (void)
SWITCH_STMT_COND (cs->switch_stmt),
bool_cond_p, cs->outside_range_p);
+ /* For the benefit of block_may_fallthru remember if the switch body
+ contains a default: case label and no break; stmts. */
+ if (cs->has_default_p && !cs->break_stmt_seen_p)
+ SWITCH_STMT_CANNOT_FALLTHRU_P (cs->switch_stmt) = 1;
+ gcc_assert (!cs->in_loop_body_p);
splay_tree_delete (cs->cases);
switch_stack = switch_stack->next;
free (cs);
}
+/* Note that a BREAK_STMT is about to be added. If it is inside of
+ a SWITCH_STMT and not inside of a loop body inside of it, note
+ in switch_stack we've seen a BREAK_STMT. */
+
+void
+note_break_stmt (void)
+{
+ if (switch_stack && !switch_stack->in_loop_body_p)
+ switch_stack->break_stmt_seen_p = true;
+}
+
+/* Note the start of processing of an iteration statement's body.
+ The note_break_stmt function will do nothing while processing it.
+ Return a flag that should be passed to note_iteration_stmt_body_end. */
+
+bool
+note_iteration_stmt_body_start (void)
+{
+ if (!switch_stack)
+ return false;
+ bool ret = switch_stack->in_loop_body_p;
+ switch_stack->in_loop_body_p = true;
+ return ret;
+}
+
+/* Note the end of processing of an iteration statement's body. */
+
+void
+note_iteration_stmt_body_end (bool prev)
+{
+ if (switch_stack)
+ switch_stack->in_loop_body_p = prev;
+}
+
/* Convert a case constant VALUE in a switch to the type TYPE of the switch
condition. Note that if TYPE and VALUE are already integral we don't
really do the conversion because the language-independent
@@ -3508,6 +3557,9 @@ finish_case_label (location_t loc, tree
cp_binding_level *p;
tree type;
+ if (low_value == NULL_TREE && high_value == NULL_TREE)
+ switch_stack->has_default_p = true;
+
if (processing_template_decl)
{
tree label;
--- gcc/cp/parser.c.jj 2017-11-23 21:17:52.000000000 +0100
+++ gcc/cp/parser.c 2017-11-25 21:29:52.644946109 +0100
@@ -12256,7 +12256,9 @@ cp_parser_iteration_statement (cp_parser
parens.require_close (parser);
/* Parse the dependent statement. */
parser->in_statement = IN_ITERATION_STMT;
+ bool prev = note_iteration_stmt_body_start ();
cp_parser_already_scoped_statement (parser, if_p, guard_tinfo);
+ note_iteration_stmt_body_end (prev);
parser->in_statement = in_statement;
/* We're done with the while-statement. */
finish_while_stmt (statement);
@@ -12271,7 +12273,9 @@ cp_parser_iteration_statement (cp_parser
statement = begin_do_stmt ();
/* Parse the body of the do-statement. */
parser->in_statement = IN_ITERATION_STMT;
+ bool prev = note_iteration_stmt_body_start ();
cp_parser_implicitly_scoped_statement (parser, NULL, guard_tinfo);
+ note_iteration_stmt_body_end (prev);
parser->in_statement = in_statement;
finish_do_body (statement);
/* Look for the `while' keyword. */
@@ -12303,7 +12307,9 @@ cp_parser_iteration_statement (cp_parser
/* Parse the body of the for-statement. */
parser->in_statement = IN_ITERATION_STMT;
+ bool prev = note_iteration_stmt_body_start ();
cp_parser_already_scoped_statement (parser, if_p, guard_tinfo);
+ note_iteration_stmt_body_end (prev);
parser->in_statement = in_statement;
/* We're done with the for-statement. */
--- gcc/cp/cp-objcp-common.c.jj 2017-11-24 22:38:51.214379987 +0100
+++ gcc/cp/cp-objcp-common.c 2017-11-25 20:43:09.221755658 +0100
@@ -349,6 +349,11 @@ cxx_block_may_fallthru (const_tree stmt)
case THROW_EXPR:
return false;
+ case SWITCH_STMT:
+ return (!SWITCH_STMT_CANNOT_FALLTHRU_P (stmt)
+ || SWITCH_STMT_BODY (stmt) == NULL_TREE
+ || block_may_fallthru (SWITCH_STMT_BODY (stmt)));
+
default:
return true;
}
--- gcc/cp/semantics.c.jj 2017-11-23 21:13:28.000000000 +0100
+++ gcc/cp/semantics.c 2017-11-25 21:07:22.443247156 +0100
@@ -1118,6 +1118,7 @@ finish_break_stmt (void)
understand. */
if (!block_may_fallthru (cur_stmt_list))
return void_node;
+ note_break_stmt ();
return add_stmt (build_stmt (input_location, BREAK_STMT));
}
--- gcc/cp/pt.c.jj 2017-11-23 21:13:28.000000000 +0100
+++ gcc/cp/pt.c 2017-11-25 21:32:26.956082032 +0100
@@ -16122,7 +16122,11 @@ tsubst_expr (tree t, tree args, tsubst_f
finish_for_cond (tmp, stmt, false);
tmp = RECUR (FOR_EXPR (t));
finish_for_expr (tmp, stmt);
- RECUR (FOR_BODY (t));
+ {
+ bool prev = note_iteration_stmt_body_start ();
+ RECUR (FOR_BODY (t));
+ note_iteration_stmt_body_end (prev);
+ }
finish_for_stmt (stmt);
break;
@@ -16146,7 +16150,9 @@ tsubst_expr (tree t, tree args, tsubst_f
else
stmt = cp_convert_range_for (stmt, decl, expr, NULL_TREE, 0,
RANGE_FOR_IVDEP (t));
+ bool prev = note_iteration_stmt_body_start ();
RECUR (RANGE_FOR_BODY (t));
+ note_iteration_stmt_body_end (prev);
finish_for_stmt (stmt);
}
break;
@@ -16155,13 +16161,21 @@ tsubst_expr (tree t, tree args, tsubst_f
stmt = begin_while_stmt ();
tmp = RECUR (WHILE_COND (t));
finish_while_stmt_cond (tmp, stmt, false);
- RECUR (WHILE_BODY (t));
+ {
+ bool prev = note_iteration_stmt_body_start ();
+ RECUR (WHILE_BODY (t));
+ note_iteration_stmt_body_end (prev);
+ }
finish_while_stmt (stmt);
break;
case DO_STMT:
stmt = begin_do_stmt ();
- RECUR (DO_BODY (t));
+ {
+ bool prev = note_iteration_stmt_body_start ();
+ RECUR (DO_BODY (t));
+ note_iteration_stmt_body_end (prev);
+ }
finish_do_body (stmt);
tmp = RECUR (DO_COND (t));
finish_do_stmt (tmp, stmt, false);
--- gcc/testsuite/g++.dg/warn/pr81275-1.C.jj 2017-11-25 20:40:07.679937379 +0100
+++ gcc/testsuite/g++.dg/warn/pr81275-1.C 2017-11-25 21:44:13.303549363 +0100
@@ -0,0 +1,165 @@
+// PR sanitizer/81875
+// { dg-do compile }
+// { dg-options "-Wreturn-type" }
+
+struct C { C (); ~C (); };
+
+int
+f1 (int a, int b)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ return 7;
+ case 24:
+ return 19;
+ default:
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-bogus "control reaches end of non-void function" }
+
+int
+f2 (int a, int b, int c, int d)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ while (c >= 10)
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ return 7;
+ case 29:
+ switch (d)
+ {
+ case 35:
+ break;
+ default:
+ return 9;
+ }
+ return 8;
+ case 24:
+ do
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ while (c >= 10);
+ return 19;
+ default:
+ for (int e = 0; e < c; ++e)
+ if (e == d)
+ break;
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-bogus "control reaches end of non-void function" }
+
+template <int N>
+int
+f3 (int a, int b)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ return 7;
+ case 24:
+ return 19;
+ default:
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-bogus "control reaches end of non-void function" }
+
+template <int N>
+int
+f4 (int a, int b, int c, int d)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ while (c >= 10)
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ return 7;
+ case 29:
+ switch (d)
+ {
+ case 35:
+ break;
+ default:
+ return 9;
+ }
+ return 8;
+ case 24:
+ do
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ while (c >= 10);
+ return 19;
+ default:
+ for (int e = 0; e < c; ++e)
+ if (e == d)
+ break;
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-bogus "control reaches end of non-void function" }
+
+int
+f5 (int a, int b)
+{
+ return f3 <0> (a, b);
+}
+
+int
+f6 (int a, int b, int c, int d)
+{
+ return f4 <2> (a, b, c, d);
+}
--- gcc/testsuite/g++.dg/warn/pr81275-2.C.jj 2017-11-25 21:37:40.291296947 +0100
+++ gcc/testsuite/g++.dg/warn/pr81275-2.C 2017-11-25 21:44:21.796446769 +0100
@@ -0,0 +1,165 @@
+// PR sanitizer/81875
+// { dg-do compile }
+// { dg-options "-Wreturn-type" }
+
+struct C { C (); ~C (); };
+
+int
+f1 (int a, int b)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ return 7;
+ case 24:
+ return 19;
+ case 25:
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-warning "control reaches end of non-void function" }
+
+int
+f2 (int a, int b, int c, int d)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ while (c >= 10)
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ return 7;
+ case 29:
+ switch (d)
+ {
+ case 35:
+ break;
+ default:
+ return 9;
+ }
+ return 8;
+ case 24:
+ do
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ while (c >= 10);
+ return 19;
+ case 25:
+ for (int e = 0; e < c; ++e)
+ if (e == d)
+ break;
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-warning "control reaches end of non-void function" }
+
+template <int N>
+int
+f3 (int a, int b)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ return 7;
+ case 24:
+ return 19;
+ case 25:
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-warning "control reaches end of non-void function" }
+
+template <int N>
+int
+f4 (int a, int b, int c, int d)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ while (c >= 10)
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ return 7;
+ case 29:
+ switch (d)
+ {
+ case 35:
+ break;
+ default:
+ return 9;
+ }
+ return 8;
+ case 24:
+ do
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ while (c >= 10);
+ return 19;
+ case 25:
+ for (int e = 0; e < c; ++e)
+ if (e == d)
+ break;
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-warning "control reaches end of non-void function" }
+
+int
+f5 (int a, int b)
+{
+ return f3 <0> (a, b);
+}
+
+int
+f6 (int a, int b, int c, int d)
+{
+ return f4 <2> (a, b, c, d);
+}
--- gcc/testsuite/g++.dg/warn/pr81275-3.C.jj 2017-11-25 21:45:03.282945613 +0100
+++ gcc/testsuite/g++.dg/warn/pr81275-3.C 2017-11-25 21:47:08.797429400 +0100
@@ -0,0 +1,173 @@
+// PR sanitizer/81875
+// { dg-do compile }
+// { dg-options "-Wreturn-type" }
+
+struct C { C (); ~C (); };
+
+int
+f1 (int a, int b, int c)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ return 7;
+ case 24:
+ if (c == 5)
+ break;
+ return 19;
+ default:
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-warning "control reaches end of non-void function" }
+
+int
+f2 (int a, int b, int c, int d)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ while (c >= 10)
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ return 7;
+ case 29:
+ switch (d)
+ {
+ case 35:
+ break;
+ default:
+ return 9;
+ }
+ if (c == d + 20)
+ break;
+ return 8;
+ case 24:
+ do
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ while (c >= 10);
+ return 19;
+ default:
+ for (int e = 0; e < c; ++e)
+ if (e == d)
+ break;
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-warning "control reaches end of non-void function" }
+
+template <int N>
+int
+f3 (int a, int b, int c)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ return 7;
+ case 24:
+ if (c == 5)
+ break;
+ return 19;
+ default:
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-warning "control reaches end of non-void function" }
+
+template <int N>
+int
+f4 (int a, int b, int c, int d)
+{
+ C f;
+ switch (a)
+ {
+ case 0:
+ switch (b)
+ {
+ case 13:
+ while (c >= 10)
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ return 7;
+ case 29:
+ switch (d)
+ {
+ case 35:
+ break;
+ default:
+ return 9;
+ }
+ if (c == d + 20)
+ break;
+ return 8;
+ case 24:
+ do
+ {
+ if (c == d)
+ break;
+ c--;
+ }
+ while (c >= 10);
+ return 19;
+ default:
+ for (int e = 0; e < c; ++e)
+ if (e == d)
+ break;
+ return 0;
+ }
+ break;
+ default:
+ return 0;
+ case 9:
+ return 17;
+ }
+} // { dg-warning "control reaches end of non-void function" }
+
+int
+f5 (int a, int b, int c)
+{
+ return f3 <0> (a, b, c);
+}
+
+int
+f6 (int a, int b, int c, int d)
+{
+ return f4 <2> (a, b, c, d);
+}
Jakub