[Bug c/46921] Lost side effect when struct initializer expression uses comma operator

[jsm28 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=46921

--- Comment #5 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
Author: jsm28
Date: Tue Mar 13 18:10:09 2018
New Revision: 258497

URL: https://gcc.gnu.org/viewcvs?rev=258497&root=gcc&view=rev
Log:
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  <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.

gcc/testsuite:
2018-03-13  David Pagan  <dave.pagan@oracle.com>

        PR c/46921
        * gcc.dg/pr46921.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/pr46921.c
Modified:
    trunk/gcc/c/ChangeLog
    trunk/gcc/c/c-typeck.c
    trunk/gcc/testsuite/ChangeLog