From ada6bad9780d405aea40acbea4f0813b05e3733a Mon Sep 17 00:00:00 2001 From: David Pagan Date: Tue, 13 Mar 2018 18:10:09 +0000 Subject: [PATCH] PR c/46921 Lost side effect when struct initializer expression uses comma operator 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. gcc/c: 2018-03-13 David Pagan PR c/46921 * c-typeck.c (output_init_element): Ensure field initializer expression is always evaluated if there are side effects. gcc/testsuite: 2018-03-13 David Pagan PR c/46921 * gcc.dg/pr46921.c: New test. From-SVN: r258497 --- gcc/c/ChangeLog | 6 +++++ gcc/c/c-typeck.c | 6 +++-- gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/gcc.dg/pr46921.c | 40 ++++++++++++++++++++++++++++++++++ 4 files changed, 55 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/pr46921.c diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog index 599ffa2cbe3..8147835935c 100644 --- a/gcc/c/ChangeLog +++ b/gcc/c/ChangeLog @@ -1,3 +1,9 @@ +2018-03-13 David Pagan + + PR c/46921 + * c-typeck.c (output_init_element): Ensure field initializer + expression is always evaluated if there are side effects. + 2018-03-06 Jakub Jelinek PR c/84721 diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c index 1eae4ea849c..2ac85003ebb 100644 --- a/gcc/c/c-typeck.c +++ b/gcc/c/c-typeck.c @@ -9208,12 +9208,14 @@ output_init_element (location_t loc, tree value, tree origtype, "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; diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 8f15d5fc6aa..c518ebeff22 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2018-03-13 David Pagan + + PR c/46921 + * gcc.dg/pr46921.c: New test. + 2018-03-13 Martin Sebor PR tree-optimization/84725 diff --git a/gcc/testsuite/gcc.dg/pr46921.c b/gcc/testsuite/gcc.dg/pr46921.c new file mode 100644 index 00000000000..17dfedd7e0a --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr46921.c @@ -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; +} -- 2.30.2