From 5e71f86dffcd87a68ccb9e11a661d931e0e995e7 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 22 Sep 2023 22:22:12 +0200
Subject: [PATCH] alloc-util: add realloc0() helper than is like realloc() but
 zero-initializes appended space

---
 src/basic/alloc-util.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/basic/alloc-util.h b/src/basic/alloc-util.h
index 156c973e692..3ef834aceee 100644
--- a/src/basic/alloc-util.h
+++ b/src/basic/alloc-util.h
@@ -254,4 +254,24 @@ static inline void free_many_charp(char **c, size_t n) {
         free_many((void**) c, n);
 }
 
+_alloc_(2) static inline void *realloc0(void *p, size_t new_size) {
+        size_t old_size;
+        void *q;
+
+        /* Like realloc(), but initializes anything appended to zero */
+
+        old_size = MALLOC_SIZEOF_SAFE(p);
+
+        q = realloc(p, new_size);
+        if (!q)
+                return NULL;
+
+        new_size = MALLOC_SIZEOF_SAFE(q); /* Update with actually allocated space */
+
+        if (new_size > old_size)
+                memset((uint8_t*) q + old_size, 0, new_size - old_size);
+
+        return q;
+}
+
 #include "memory-util.h"