* [PATCH] PR c/46921 Lost side effect when struct initializer expression uses comma operator
@ 2018-02-27 0:05 dave.pagan
2018-03-13 18:23 ` Joseph Myers
0 siblings, 1 reply; 2+ messages in thread
From: dave.pagan @ 2018-02-27 0:05 UTC (permalink / raw)
To: Gcc Patch List; +Cc: Joseph Myers
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This patch fixes improper handling of comma operator expression in a
struct field initializer as described in:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46921
Currently, function output_init_element () does not evaluate the left
hand expression in a comma operator that's used for a struct initializer
field if the right hand side is zero-sized. However, the left hand
expression must be evaluated if it's found to have side effects (for
example, a function call).
Patch was successfully bootstrapped and tested on x86_64-linux.
--Dave
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/c
2018-02-26 David Pagan <dave.pagan@oracle.com>
PR c/46921
* c-typeck.c (output_init_element): Ensure field initializer
expression is always evaluated if there are side effects.
/testsuite
2018-02-26 David Pagan <dave.pagan@oracle.com>
PR c/46921
* gcc.dg/pr46921.c: New test.
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Index: gcc/c/c-typeck.c
===================================================================
--- gcc/c/c-typeck.c (revision 257975)
+++ gcc/c/c-typeck.c (working copy)
@@ -9208,12 +9208,14 @@ output_init_element (location_t loc, tree value, t
"enum conversion in initialization is invalid in C++");
}
- /* If this field is empty (and not at the end of structure),
- don't do anything other than checking the initializer. */
+ /* If this field is empty and does not have side effects (and is not at
+ the end of structure), don't do anything other than checking the
+ initializer. */
if (field
&& (TREE_TYPE (field) == error_mark_node
|| (COMPLETE_TYPE_P (TREE_TYPE (field))
&& integer_zerop (TYPE_SIZE (TREE_TYPE (field)))
+ && !TREE_SIDE_EFFECTS (new_value)
&& (TREE_CODE (constructor_type) == ARRAY_TYPE
|| DECL_CHAIN (field)))))
return;
Index: gcc/testsuite/gcc.dg/pr46921.c
===================================================================
--- gcc/testsuite/gcc.dg/pr46921.c (revision 0)
+++ gcc/testsuite/gcc.dg/pr46921.c (working copy)
@@ -0,0 +1,40 @@
+/* PR c/46921 lost side effect when struct initializer expr uses comma
+ operator */
+
+/* { dg-do run } */
+/* { dg-options "" } */
+
+extern int printf(const char *, ...);
+extern void abort (void);
+
+typedef struct __uws_0 { } uw_unit;
+uw_unit uw_unit_v = {};
+
+struct __uws_1
+{
+ struct __uws_0 __uwf_1;
+ struct __uws_1* __uwf_2;
+};
+
+static int left_hand_eval = 0;
+
+static void
+foo (const char *s)
+{
+ ++left_hand_eval;
+ printf("%s", s);
+}
+
+int
+main ()
+{
+ struct __uws_1 tmp = {(foo("Inner\n"), uw_unit_v)};
+
+ printf("Outer\n");
+ /* left hand expression in comma operator initializer must always be
+ evaluated if there are side effects. */
+ if (!left_hand_eval)
+ abort ();
+
+ return 0;
+}
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] PR c/46921 Lost side effect when struct initializer expression uses comma operator
2018-02-27 0:05 [PATCH] PR c/46921 Lost side effect when struct initializer expression uses comma operator dave.pagan
@ 2018-03-13 18:23 ` Joseph Myers
0 siblings, 0 replies; 2+ messages in thread
From: Joseph Myers @ 2018-03-13 18:23 UTC (permalink / raw)
To: dave.pagan; +Cc: Gcc Patch List
Thanks, committed.
--
Joseph S. Myers
joseph@codesourcery.com
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2018-02-27 0:05 [PATCH] PR c/46921 Lost side effect when struct initializer expression uses comma operator dave.pagan
2018-03-13 18:23 ` Joseph Myers
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