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[PATCH 7/9] Avoid undefined behavior in ada_operator_length
- From: Tom Tromey <tom at tromey dot com>
- To: gdb-patches at sourceware dot org
- Cc: Tom Tromey <tom at tromey dot com>
- Date: Mon, 27 Aug 2018 08:56:18 -0600
- Subject: [PATCH 7/9] Avoid undefined behavior in ada_operator_length
- References: <20180827145620.11055-1-tom@tromey.com>
-fsanitize=undefined pointed out this error:
runtime error: load of value 2887952, which is not a valid value for type 'exp_opcode'
This happens in gdb.ada/complete.exp when processing "complete p
my_glob". This does not parse, so the Ada parser throws an exception;
but then the code in parse_exp_in_context_1 accepts the expression
anyway. However, as no elements have been written to the expression,
undefined behavior results.
The fix is to notice this case in parse_exp_in_context_1. This patch
also adds an assertion to prefixify_expression to enforce this
pre-existing constraint.
ChangeLog
2018-08-27 Tom Tromey <tom@tromey.com>
* parse.c (prefixify_expression): Add assert.
(parse_exp_in_context_1): Throw exception if the expression is
empty.
---
gdb/ChangeLog | 8 +++++++-
gdb/parse.c | 6 +++++-
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/gdb/parse.c b/gdb/parse.c
index 1b58073a529..a9b802d0e6e 100644
--- a/gdb/parse.c
+++ b/gdb/parse.c
@@ -792,6 +792,7 @@ copy_name (struct stoken token)
int
prefixify_expression (struct expression *expr)
{
+ gdb_assert (expr->nelts > 0);
int len = sizeof (struct expression) + EXP_ELEM_TO_BYTES (expr->nelts);
struct expression *temp;
int inpos = expr->nelts, outpos = 0;
@@ -1205,7 +1206,10 @@ parse_exp_in_context_1 (const char **stringptr, CORE_ADDR pc,
}
CATCH (except, RETURN_MASK_ALL)
{
- if (! parse_completion)
+ /* If parsing for completion, allow this to succeed; but if no
+ expression elements have been written, then there's nothing
+ to do, so fail. */
+ if (! parse_completion || ps.expout_ptr == 0)
throw_exception (except);
}
END_CATCH
--
2.13.6