Hi!
The recent change to clear TREE_SIDE_EFFECTS on STATEMENT_LIST containing
DEBUG_BEGIN_STMTs and a single other statement without TREE_SIDE_EFFECTS on
it breaks the C stmt expr handling. The problem is that it assumes if
TREE_SIDE_EFFECTS is clear on a STATEMENT_LIST then that means the
STATEMENT_LIST is empty, i.e. ({ }), which is no longer the case.
Fixed by skipping over DEBUG_BEGIN_STMTs from the tail to find the last
non-DEBUG_BEGIN_STMT stmt (if any, and if none, treat it like ({ }) ),
and also not processing the last non-DEBUG_BEGIN_STMT for -Wunused-value
if it is followed by DEBUG_BEGIN_STMTs.
In addition to this, the patch includes a fix from my earlier patch, where
alloc_stmt_list TREE_SIDE_EFFECTS bit is inconsistent, depending on whether
it is reused from the cache (then TREE_SIDE_EFFECTS was clear), or newly
allocated (then it was set).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2017-12-22 Jakub Jelinek <ja...@redhat.com>
PR debug/83547
* tree-iterator.c (alloc_stmt_list): Start with cleared
TREE_SIDE_EFFECTS regardless whether a new STATEMENT_LIST is allocated
or old one reused.
c/
* c-typeck.c (c_finish_stmt_expr): Ignore !TREE_SIDE_EFFECTS as
indicator of ({ }), instead skip all trailing DEBUG_BEGIN_STMTs first,
and consider empty ones if there are no other stmts. For
-Wunused-value walk all statements before the one only followed by
DEBUG_BEGIN_STMTs.
testsuite/
* gcc.c-torture/compile/pr83547.c: New test.
--- gcc/tree-iterator.c.jj 2017-12-18 14:57:11.000000000 +0100
+++ gcc/tree-iterator.c 2017-12-22 12:18:49.017432720 +0100
@@ -41,7 +41,10 @@ alloc_stmt_list (void)
TREE_SET_CODE (list, STATEMENT_LIST);
}
else
- list = make_node (STATEMENT_LIST);
+ {
+ list = make_node (STATEMENT_LIST);
+ TREE_SIDE_EFFECTS (list) = 0;
+ }
TREE_TYPE (list) = void_type_node;
return list;
}
--- gcc/c/c-typeck.c.jj 2017-12-19 18:09:05.000000000 +0100
+++ gcc/c/c-typeck.c 2017-12-22 12:29:01.213576464 +0100
@@ -10751,17 +10751,21 @@ c_finish_stmt_expr (location_t loc, tree
continue_searching:
if (TREE_CODE (last) == STATEMENT_LIST)
{
- tree_stmt_iterator i;
+ tree_stmt_iterator l = tsi_last (last);
+
+ while (!tsi_end_p (l) && TREE_CODE (tsi_stmt (l)) == DEBUG_BEGIN_STMT)
+ tsi_prev (&l);
/* This can happen with degenerate cases like ({ }). No value. */
- if (!TREE_SIDE_EFFECTS (last))
+ if (tsi_end_p (l))
return body;
/* If we're supposed to generate side effects warnings, process
all of the statements except the last. */
if (warn_unused_value)
{
- for (i = tsi_start (last); !tsi_one_before_end_p (i); tsi_next (&i))
+ for (tree_stmt_iterator i = tsi_start (last);
+ tsi_stmt (i) != tsi_stmt (l); tsi_next (&i))
{
location_t tloc;
tree t = tsi_stmt (i);
@@ -10770,13 +10774,7 @@ c_finish_stmt_expr (location_t loc, tree
emit_side_effect_warnings (tloc, t);
}
}
- else
- i = tsi_last (last);
- if (TREE_CODE (tsi_stmt (i)) == DEBUG_BEGIN_STMT)
- do
- tsi_prev (&i);
- while (TREE_CODE (tsi_stmt (i)) == DEBUG_BEGIN_STMT);
- last_p = tsi_stmt_ptr (i);
+ last_p = tsi_stmt_ptr (l);
last = *last_p;
}
--- gcc/testsuite/gcc.c-torture/compile/pr83547.c.jj 2017-12-22
12:36:06.503125477 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr83547.c 2017-12-22
12:35:45.000000000 +0100
@@ -0,0 +1,16 @@
+/* PR debug/83547 */
+
+void
+foo (void)
+{
+ if (({ 0; }))
+ ;
+ if (({ 0; 0; }))
+ ;
+ if (({ })) /* { dg-error "void value not ignored as it ought to
be" } */
+ ;
+ if (({ 0; { 0; } })) /* { dg-error "void value not ignored as it ought to
be" } */
+ ;
+ if (({ 0; {} })) /* { dg-error "void value not ignored as it ought to
be" } */
+ ;
+}
Jakub
