From 0346c2f9c3fbf387971b2a424a4e261de5409aac Mon Sep 17 00:00:00 2001
From: Andreas Pehrson <apehrson@mozilla.com>
Date: Tue, 12 Dec 2023 10:22:34 +0100
Subject: [PATCH] auto_array: protect from various calls when length_ is 0

cubeb-coreaudio-rs has hit a case when running its tests on MacOS 12
where it fails the `assert(destination && source);` in `PodCopy` because
it tried to push 0 samples to an auto_array of length 0, as the internal
auto_array buffer had not been allocated yet.
---
 src/cubeb_utils.h | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/cubeb_utils.h b/src/cubeb_utils.h
index fd7a3d74..851d24de 100644
--- a/src/cubeb_utils.h
+++ b/src/cubeb_utils.h
@@ -182,7 +182,9 @@ template <typename T> class auto_array {
     if (length_ + length > capacity_) {
       reserve(length_ + length);
     }
-    PodCopy(data_ + length_, elements, length);
+    if (data_) {
+      PodCopy(data_ + length_, elements, length);
+    }
     length_ += length;
   }
 
@@ -195,12 +197,14 @@ template <typename T> class auto_array {
     if (length_ + length > capacity_) {
       reserve(length + length_);
     }
-    PodZero(data_ + length_, length);
+    if (data_) {
+      PodZero(data_ + length_, length);
+    }
     length_ += length;
   }
 
-  /** Prepend `length` zero-ed elements to the end of the array, resizing the
-   * array if needed.
+  /** Prepend `length` zero-ed elements to the front of the array, resizing and
+   * shifting the array if needed.
    * @parameter length the number of elements to prepend to the array.
    */
   void push_front_silence(size_t length)
@@ -208,8 +212,10 @@ template <typename T> class auto_array {
     if (length_ + length > capacity_) {
       reserve(length + length_);
     }
-    PodMove(data_ + length, data_, length_);
-    PodZero(data_, length);
+    if (data_) {
+      PodMove(data_ + length, data_, length_);
+      PodZero(data_, length);
+    }
     length_ += length;
   }
 
@@ -227,6 +233,9 @@ template <typename T> class auto_array {
     if (length > length_) {
       return false;
     }
+    if (!data_) {
+      return true;
+    }
     if (elements) {
       PodCopy(elements, data_, length);
     }