Re: [PATCH] PR c/71171: Fix uninitialized source_range in c_parser_postfix_expression

[Jeff Law]

On 05/18/2016 07:08 PM, David Malcolm wrote:

PR c/71171 reports yet another instance of the src_range of a
c_expr being used without initialization.  Investigation shows
that this was due to error-handling, where the "value" field of
a c_expr is set to error_mark_node without touching the
src_range, leading to complaints from valgrind.

This seems to be a common mistake, so this patch introduces a
new method, c_expr::set_error, which sets the value to
error_mark_node whilst initializing the src_range to
UNKNOWN_LOCATION.

This fixes the valgrind issue seen in PR c/71171, along with various
similar issues seen when running the testsuite using the checker
patch I posted here:
  https://gcc.gnu.org/ml/gcc-patches/2015-12/msg00887.html
(this checker still doesn't fully work yet, but it seems to be good
for easily detecting these issues without needing Valgrind).

Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu.

OK for trunk and for gcc-6-branch?

gcc/c/ChangeLog:
        PR c/71171
        * c-parser.c (c_parser_generic_selection): Use c_expr::set_error
        in error-handling.
        (c_parser_postfix_expression): Likewise.
        * c-tree.h (c_expr::set_error): New method.
        * c-typeck.c (parser_build_binary_op): In error-handling, ensure
        that result's range is initialized.

OK.
jeff