From 886b0cb22194d1b7f4b89d8e40811fa332f43f38 Mon Sep 17 00:00:00 2001
From: Ben Lawrence <ben.lawrence@nanoporetech.com>
Date: Wed, 24 Jan 2024 17:20:27 +0000
Subject: [PATCH] Avoid NULL pointer dereference

If the allocated region is 0 bytes then it's unsafe to dereference it.

Fixes #1147.
---
 index.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/index.c b/index.c
index 0d8a2ae0..cd8b40e4 100644
--- a/index.c
+++ b/index.c
@@ -192,6 +192,7 @@ int32_t mm_idx_cal_max_occ(const mm_idx_t *mi, float f)
 	if (f <= 0.) return INT32_MAX;
 	for (i = 0; i < 1<<mi->b; ++i)
 		if (mi->B[i].h) n += kh_size((idxhash_t*)mi->B[i].h);
+	if (n == 0) return INT32_MAX;
 	a = (uint32_t*)malloc(n * 4);
 	for (i = n = 0; i < 1<<mi->b; ++i) {
 		idxhash_t *h = (idxhash_t*)mi->B[i].h;