For the left side of a concat expression, dtype is NULL and therefore
off is 0. In that case the code expects to get a datatype of
TYPE_INVALID, but this is fragile as the output of concat_subtype_id()
is undefined for n > 32 / TYPE_BITS.
To fix this, call datatype_lookup() directly passing the expected
TYPE_INVALID as argument if off is 0.
Signed-off-by: Phil Sutter <p...@nwl.cc>
---
Changes since v1:
- Understood (and reproduced) when the situation causing the undefined
behaviour happens.
- Understood what the code is supposed to do in that situation.
- Based on the information at hand, implemented a solution which avoids
undefined behaviour.
---
src/evaluate.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/src/evaluate.c b/src/evaluate.c
index 194a03495b5fd..c1ee6b1929551 100644
--- a/src/evaluate.c
+++ b/src/evaluate.c
@@ -962,7 +962,10 @@ static int expr_evaluate_concat(struct eval_ctx *ctx,
struct expr **expr)
"expressions",
i->dtype->name);
- tmp = concat_subtype_lookup(type, --off);
+ if (dtype == NULL)
+ tmp = datatype_lookup(TYPE_INVALID);
+ else
+ tmp = concat_subtype_lookup(type, --off);
expr_set_context(&ctx->ectx, tmp, tmp->size);
if (list_member_evaluate(ctx, &i) < 0)
--
2.8.2
--
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