From 11521b99661f969ba7adad9d2366108a1a001ab0 Mon Sep 17 00:00:00 2001
From: "Douglas B. Rumbaugh" <doug@douglasrumbaugh.com>
Date: Sun, 2 Nov 2025 18:29:20 -0500
Subject: Defined allocator behavior for 0 byte requests

---
 include/alloc.h        | 3 ++-
 src/alloc.c            | 5 +++++
 tests/liballoc_tests.c | 4 ++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/alloc.h b/include/alloc.h
index 6374b3a..594ef67 100644
--- a/include/alloc.h
+++ b/include/alloc.h
@@ -21,7 +21,8 @@
 
 /*
  * Returns a pointer to a new region of memory of the specified
- * size, or NULL if no memory is available.
+ * size, or NULL if no memory is available. Requests for 0 bytes of
+ * memory will also return NULL.
  */
 void *allocate(size_t);
 
diff --git a/src/alloc.c b/src/alloc.c
index 39cbf88..32eb18a 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -44,6 +44,11 @@ void *allocate(size_t size) {
     initialize();
   }
 
+  /* special case for a size 0 allocation */
+  if (size == 0) {
+    return NULL;
+  }
+
   /*
    * pad the requested size to ensure alignment using
    * the alignment one-liner we discussed in class
diff --git a/tests/liballoc_tests.c b/tests/liballoc_tests.c
index 16d50d6..a54998a 100644
--- a/tests/liballoc_tests.c
+++ b/tests/liballoc_tests.c
@@ -26,6 +26,10 @@ START_TEST(basic_allocate) {
   size_t alignment = (size_t)memory % ALIGNMENT;
   ck_assert_int_eq(alignment, 0);
 
+  /* allocating 0 size should return NULL */
+  void *memory2 = allocate(0);
+  ck_assert_ptr_eq(memory2, NULL);
+
   /* leak the memory--we aren't testing release */
 }
 END_TEST
-- 
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