Set returned index to NULL on an index build error in zran.c.

An attempt to use the returned pointer in deflate_index_extract()
will now return cleanly with an error. The returned pointer can
now also be used with deflate_index_free() even on error.

1 files changed, 4 insertions, 0 deletions

diff --git a/examples/zran.c b/examples/zran.c
index d313595..9c3e5dc 100644
--- a/examples/zran.c
+++ b/examples/zran.c
@@ -130,6 +130,10 @@ static struct deflate_index *add_point(struct deflate_index *index, int bits,
 
 // See comments in zran.h.
 int deflate_index_build(FILE *in, off_t span, struct deflate_index **built) {
+    // If this returns with an error, any attempt to use the index will cleanly
+    // return an error.
+    *built = NULL;
+
     // Set up inflation state.
     z_stream strm = {0};        // inflate engine (gets fired up later)
     unsigned char buf[CHUNK];   // input buffer