dstring: Initialize freshly-allocated strings

Previously, a string allocated with dstralloc() had length 0 but no
terminating NUL byte there.  This was problematic if such a string was
used without being modified.

In particular, this was reproducible with bfs -ok by not typing any
response to the prompt.  In that case, uninitialized memory was being
tested for a y/n response, with unpredictable results.

1 files changed, 1 insertions, 0 deletions

diff --git a/dstring.c b/dstring.c
index 98678c0..f4a865a 100644
--- a/dstring.c
+++ b/dstring.c
@@ -43,6 +43,7 @@ char *dstralloc(size_t capacity) {
 
 	header->capacity = capacity;
 	header->length = 0;
+	header->data[0] = '\0';
 	return header->data;
 }