Hi!
A nested switch that can fallthrough (either because it has break stmts
or because it doesn't have default: and doesn't cover all cases) isn't
unfortunately reported with -Wimplicit-fallthrough, because we first
gimplify the nested switch and then we just see a label added implicitly
for break; or for the default: case if it was missing and the cases don't
cover all possible values and punt on that.
The following patch fixes it by telling the -Wimplicit-fallthrough
code about the special labels added for break; or missing default:
through a new SWITCH_BREAK_LABEL_P flag. Additionally it makes sure
that GIMPLE_LABEL is emitted still inside of the switch's body sequence
and if it is a nested switch, it wraps the GIMPLE_SWITCH with the body
that ends in a GIMPLE_LABEL with SWITCH_BREAK_LABEL_P in a GIMPLE_BIND
(without vars or blocks). With this, the -Wimplicit-fallthrough code
can recognize this and treat the whole switch that can fall through as
a single statement for the purpose of the warning.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2017-11-30 Jakub Jelinek <ja...@redhat.com>
PR c/79153
* tree.h (SWITCH_BREAK_LABEL_P): Define.
* gimplify.c (collect_fallthrough_labels): Handle GIMPLE_BIND
starting with a GIMPLE_SWITCH and ending with GIMPLE_LABEL with
SWITCH_BREAK_LABEL_P set on the label.
(gimplify_switch_expr): Set SWITCH_BREAK_LABEL_P on the label
added for default case if it was missing and not all cases covered.
Wrap GIMPLE_SWITCH and the switch_body_seq into a GIMPLE_BIND if
switch_body_seq ends with a GIMPLE_LABEL with SWITCH_BREAK_LABEL_P
set on the label.
* tree-chrec.c (evolution_function_is_univariate_p): Add return true;
to avoid -Wimplicit-fallthrough warning.
* config/i386/i386.c (ix86_expand_special_args_builtin): Add
FALLTHRU comment to avoid -Wimplicit-fallthrough warning.
c/
* c-parser.c: Include tree-iterator.h.
(c_parser_switch_statement): Emit LABEL_EXPR for the break label
into SWITCH_BODY instead of after it and set SWITCH_BREAK_LABEL_P
on it.
cp/
* cp-gimplify.c (genericize_switch_stmt): Emit LABEL_EXPR for the
break label into SWITCH_BODY instead of after it and set
SWITCH_BREAK_LABEL_P on it.
* parser.c (cp_parser_objc_expression): Add FALLTHRU comment to avoid
-Wimplicit-fallthrough warning.
fortran/
* match.c (gfc_match): Add FALLTHRU comment to avoid
-Wimplicit-fallthrough warning.
testsuite/
* c-c++-common/Wimplicit-fallthrough-7.c: Adjust expected warning
line.
* c-c++-common/Wimplicit-fallthrough-36.c: New test.
--- gcc/tree.h.jj 2017-11-28 22:21:17.000000000 +0100
+++ gcc/tree.h 2017-11-30 17:55:35.299197618 +0100
@@ -766,6 +766,11 @@ extern void omp_clause_range_check_faile
#define FALLTHROUGH_LABEL_P(NODE) \
(LABEL_DECL_CHECK (NODE)->base.private_flag)
+/* Set on the artificial label created for break; stmt from a switch.
+ This is used to implement -Wimplicit-fallthrough. */
+#define SWITCH_BREAK_LABEL_P(NODE) \
+ (LABEL_DECL_CHECK (NODE)->base.protected_flag)
+
/* Nonzero means this expression is volatile in the C sense:
its address should be of type `volatile WHATEVER *'.
In other words, the declared item is volatile qualified.
--- gcc/gimplify.c.jj 2017-11-28 12:11:40.000000000 +0100
+++ gcc/gimplify.c 2017-11-30 19:04:32.694173903 +0100
@@ -1897,6 +1897,27 @@ collect_fallthrough_labels (gimple_stmt_
do
{
+ if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_BIND)
+ {
+ /* Recognize the special GIMPLE_BIND added by gimplify_switch_expr,
+ which starts on a GIMPLE_SWITCH and ends with a break label.
+ Handle that as a single statement that can fall through. */
+ gbind *bind = as_a <gbind *> (gsi_stmt (*gsi_p));
+ gimple *first = gimple_seq_first_stmt (gimple_bind_body (bind));
+ gimple *last = gimple_seq_last_stmt (gimple_bind_body (bind));
+ if (last
+ && gimple_code (first) == GIMPLE_SWITCH
+ && gimple_code (last) == GIMPLE_LABEL)
+ {
+ tree label = gimple_label_label (as_a <glabel *> (last));
+ if (SWITCH_BREAK_LABEL_P (label))
+ {
+ prev = bind;
+ gsi_next (gsi_p);
+ continue;
+ }
+ }
+ }
if (gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_BIND
|| gimple_code (gsi_stmt (*gsi_p)) == GIMPLE_TRY)
{
@@ -2315,6 +2336,7 @@ gimplify_switch_expr (tree *expr_p, gimp
preprocess_case_label_vec_for_gimple (labels, index_type,
&default_case);
+ bool add_bind = false;
if (!default_case)
{
glabel *new_default;
@@ -2322,14 +2344,46 @@ gimplify_switch_expr (tree *expr_p, gimp
default_case
= build_case_label (NULL_TREE, NULL_TREE,
create_artificial_label (UNKNOWN_LOCATION));
+ if (old_in_switch_expr)
+ {
+ SWITCH_BREAK_LABEL_P (CASE_LABEL (default_case)) = 1;
+ add_bind = true;
+ }
new_default = gimple_build_label (CASE_LABEL (default_case));
gimplify_seq_add_stmt (&switch_body_seq, new_default);
}
+ else if (old_in_switch_expr)
+ {
+ gimple *last = gimple_seq_last_stmt (switch_body_seq);
+ if (last && gimple_code (last) == GIMPLE_LABEL)
+ {
+ tree label = gimple_label_label (as_a <glabel *> (last));
+ if (SWITCH_BREAK_LABEL_P (label))
+ add_bind = true;
+ }
+ }
switch_stmt = gimple_build_switch (SWITCH_COND (switch_expr),
- default_case, labels);
- gimplify_seq_add_stmt (pre_p, switch_stmt);
- gimplify_seq_add_seq (pre_p, switch_body_seq);
+ default_case, labels);
+ /* For the benefit of -Wimplicit-fallthrough, if switch_body_seq
+ ends with a GIMPLE_LABEL holding SWITCH_BREAK_LABEL_P LABEL_DECL,
+ wrap the GIMPLE_SWITCH up to that GIMPLE_LABEL into a GIMPLE_BIND,
+ so that we can easily find the start and end of the switch
+ statement. */
+ if (add_bind)
+ {
+ gimple_seq bind_body = NULL;
+ gimplify_seq_add_stmt (&bind_body, switch_stmt);
+ gimple_seq_add_seq (&bind_body, switch_body_seq);
+ gbind *bind = gimple_build_bind (NULL_TREE, bind_body, NULL_TREE);
+ gimple_set_location (bind, EXPR_LOCATION (switch_expr));
+ gimplify_seq_add_stmt (pre_p, bind);
+ }
+ else
+ {
+ gimplify_seq_add_stmt (pre_p, switch_stmt);
+ gimplify_seq_add_seq (pre_p, switch_body_seq);
+ }
labels.release ();
}
else
--- gcc/tree-chrec.c.jj 2017-10-11 22:37:51.000000000 +0200
+++ gcc/tree-chrec.c 2017-11-30 20:39:01.613902149 +0100
@@ -1161,6 +1161,7 @@ evolution_function_is_univariate_p (cons
return false;
break;
}
+ return true;
default:
return true;
--- gcc/config/i386/i386.c.jj 2017-11-30 09:42:46.000000000 +0100
+++ gcc/config/i386/i386.c 2017-11-30 20:40:02.484133842 +0100
@@ -34985,6 +34985,7 @@ ix86_expand_special_args_builtin (const
default:
break;
}
+ /* FALLTHRU */
case V64QI_FTYPE_PCCHAR_V64QI_UDI:
case V32QI_FTYPE_PCCHAR_V32QI_USI:
case V16QI_FTYPE_PCCHAR_V16QI_UHI:
--- gcc/c/c-parser.c.jj 2017-11-30 12:13:49.000000000 +0100
+++ gcc/c/c-parser.c 2017-11-30 18:35:03.735146924 +0100
@@ -67,6 +67,7 @@ along with GCC; see the file COPYING3.
#include "run-rtl-passes.h"
#include "intl.h"
#include "c-family/name-hint.h"
+#include "tree-iterator.h"
/* We need to walk over decls with incomplete struct/union/enum types
after parsing the whole translation unit.
@@ -5846,14 +5847,15 @@ c_parser_switch_statement (c_parser *par
if (!open_brace_p && c_parser_peek_token (parser)->type != CPP_SEMICOLON)
warn_for_multistatement_macros (loc_after_labels, next_loc, switch_loc,
RID_SWITCH);
- c_finish_case (body, ce.original_type);
if (c_break_label)
{
location_t here = c_parser_peek_token (parser)->location;
tree t = build1 (LABEL_EXPR, void_type_node, c_break_label);
SET_EXPR_LOCATION (t, here);
- add_stmt (t);
+ SWITCH_BREAK_LABEL_P (c_break_label) = 1;
+ append_to_statement_list_force (t, &body);
}
+ c_finish_case (body, ce.original_type);
c_break_label = save_break;
add_stmt (c_end_compound_stmt (switch_loc, block, flag_isoc99));
c_parser_maybe_reclassify_token (parser);
--- gcc/cp/cp-gimplify.c.jj 2017-11-28 22:23:34.000000000 +0100
+++ gcc/cp/cp-gimplify.c 2017-11-30 19:26:36.432776337 +0100
@@ -330,11 +330,13 @@ genericize_switch_stmt (tree *stmt_p, in
cp_walk_tree (&type, cp_genericize_r, data, NULL);
*walk_subtrees = 0;
+ if (TREE_USED (break_block))
+ SWITCH_BREAK_LABEL_P (break_block) = 1;
+ finish_bc_block (&body, bc_break, break_block);
*stmt_p = build2_loc (stmt_locus, SWITCH_EXPR, type, cond, body);
SWITCH_ALL_CASES_P (*stmt_p) = SWITCH_STMT_ALL_CASES_P (stmt);
gcc_checking_assert (!SWITCH_STMT_NO_BREAK_P (stmt)
|| !TREE_USED (break_block));
- finish_bc_block (stmt_p, bc_break, break_block);
}
/* Genericize a CONTINUE_STMT node *STMT_P. */
--- gcc/cp/parser.c.jj 2017-11-30 09:42:44.000000000 +0100
+++ gcc/cp/parser.c 2017-11-30 20:40:37.868687216 +0100
@@ -29003,6 +29003,7 @@ cp_parser_objc_expression (cp_parser* pa
default:
break;
}
+ /* FALLTHRU */
default:
error_at (kwd->location,
"misplaced %<@%D%> Objective-C++ construct",
--- gcc/fortran/match.c.jj 2017-10-28 09:00:47.000000000 +0200
+++ gcc/fortran/match.c 2017-11-30 20:41:45.464834013 +0100
@@ -1240,6 +1240,7 @@ loop:
default:
gfc_internal_error ("gfc_match(): Bad match code %c", c);
}
+ /* FALLTHRU */
default:
--- gcc/testsuite/c-c++-common/Wimplicit-fallthrough-7.c.jj 2017-04-28
22:17:03.000000000 +0200
+++ gcc/testsuite/c-c++-common/Wimplicit-fallthrough-7.c 2017-11-30
19:14:47.535557117 +0100
@@ -51,9 +51,9 @@ f (int i)
{
case 1:
{
- switch (i + 2)
+ switch (i + 2) /* { dg-warning "statement may fall through" } */
case 4:
- bar (1); /* { dg-warning "statement may fall through" } */
+ bar (1);
case 5:
bar (5);
return;
--- gcc/testsuite/c-c++-common/Wimplicit-fallthrough-36.c.jj 2017-11-30
19:11:32.029979082 +0100
+++ gcc/testsuite/c-c++-common/Wimplicit-fallthrough-36.c 2017-11-30
19:11:07.000000000 +0100
@@ -0,0 +1,72 @@
+/* PR c/79153 */
+/* { dg-do compile } */
+/* { dg-options "-Wimplicit-fallthrough" } */
+
+int
+test (int v1, int v2)
+{
+ switch (v1)
+ {
+ case 3:
+ switch (v2) /* { dg-warning "this statement may fall through" } */
+ {
+ case 1:
+ return 28;
+ case 2:
+ return 38;
+ case 3:
+ return 88;
+ default:
+ break;
+ }
+ case 4: /* { dg-message "here" } */
+ return 168;
+ case 5:
+ switch (v2) /* { dg-warning "this statement may fall through" } */
+ {
+ case 4:
+ break;
+ case 5:
+ return 38;
+ case 6:
+ return 88;
+ }
+ case 6: /* { dg-message "here" } */
+ return 169;
+ case 7:
+ switch (v2) /* { dg-warning "this statement may fall through" } */
+ {
+ case 7:
+ return 38;
+ case 8:
+ return 88;
+ }
+ case 8: /* { dg-message "here" } */
+ return 170;
+ case 9:
+ switch (v2) /* { dg-bogus "this statement may fall through" } */
+ {
+ case 9:
+ return 38;
+ case 10:
+ return 88;
+ default:
+ return 89;
+ }
+ case 10:
+ return 171;
+ case 11:
+ switch (v2) /* { dg-bogus "this statement may fall through" } */
+ {
+ case -__INT_MAX__ - 1 ... 31:
+ return 38;
+ case 32:
+ return 88;
+ case 33 ... __INT_MAX__:
+ return 89;
+ }
+ case 12:
+ return 172;
+ }
+ return -1;
+}
Jakub
