diff --git a/src/util/alloc.c b/src/util/alloc.c
index 6ec173d04..998b0aea1 100644
--- a/src/util/alloc.c
+++ b/src/util/alloc.c
@@ -8,8 +8,9 @@
 #include "alloc.h"
 #include "runtime.h"
 
-#include "allocators/failalloc.h"
 #include "allocators/stdalloc.h"
+#include "allocators/debugalloc.h"
+#include "allocators/failalloc.h"
 #include "allocators/win32_leakcheck.h"
 
 /* Fail any allocation until git_libgit2_init is called. */
@@ -88,6 +89,8 @@ static int setup_default_allocator(void)
 {
 #if defined(GIT_WIN32_LEAKCHECK)
 	return git_win32_leakcheck_init_allocator(&git__allocator);
+#elif defined(GIT_DEBUG_STRICT_ALLOC)
+	return git_debugalloc_init_allocator(&git__allocator);
 #else
 	return git_stdalloc_init_allocator(&git__allocator);
 #endif
diff --git a/src/util/allocators/debugalloc.c b/src/util/allocators/debugalloc.c
new file mode 100644
index 000000000..44022cd78
--- /dev/null
+++ b/src/util/allocators/debugalloc.c
@@ -0,0 +1,73 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#include "debugalloc.h"
+
+static void *debugalloc__malloc(size_t len, const char *file, int line)
+{
+	unsigned char *ptr;
+	size_t total = len + sizeof(size_t);
+
+	GIT_UNUSED(file);
+	GIT_UNUSED(line);
+
+	if (!len || (ptr = malloc(total)) == NULL)
+		return NULL;
+
+	memcpy(ptr, &len, sizeof(size_t));
+	return ptr + sizeof(size_t);
+}
+
+static void *debugalloc__realloc(void *_ptr, size_t len, const char *file, int line)
+{
+	unsigned char *ptr = _ptr, *newptr;
+	size_t original_len;
+	size_t total = len + sizeof(size_t);
+
+	GIT_UNUSED(file);
+	GIT_UNUSED(line);
+
+	if (!len && !ptr)
+		return NULL;
+
+	if (!len) {
+		free(ptr - sizeof(size_t));
+		return NULL;
+	}
+
+	if ((newptr = malloc(total)) == NULL)
+		return NULL;
+
+	if (ptr) {
+		memcpy(&original_len, ptr - sizeof(size_t), sizeof(size_t));
+		memcpy(newptr + sizeof(size_t), ptr, min(len, original_len));
+
+		memset(ptr - sizeof(size_t), 0xfd, original_len + sizeof(size_t));
+		free(ptr - sizeof(size_t));
+	}
+
+	memcpy(newptr, &len, sizeof(size_t));
+	return newptr + sizeof(size_t);
+}
+
+static void debugalloc__free(void *_ptr)
+{
+	unsigned char *ptr = _ptr;
+
+	if (!ptr)
+		return;
+
+	free(ptr - sizeof(size_t));
+}
+
+int git_debugalloc_init_allocator(git_allocator *allocator)
+{
+	allocator->gmalloc = debugalloc__malloc;
+	allocator->grealloc = debugalloc__realloc;
+	allocator->gfree = debugalloc__free;
+	return 0;
+}
diff --git a/src/util/allocators/debugalloc.h b/src/util/allocators/debugalloc.h
new file mode 100644
index 000000000..dea0ca31c
--- /dev/null
+++ b/src/util/allocators/debugalloc.h
@@ -0,0 +1,17 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_allocators_debugalloc_h__
+#define INCLUDE_allocators_debugalloc_h__
+
+#include "git2_util.h"
+
+#include "alloc.h"
+
+int git_debugalloc_init_allocator(git_allocator *allocator);
+
+#endif
diff --git a/src/util/allocators/stdalloc.c b/src/util/allocators/stdalloc.c
index f2d72a7e6..65ec40fbe 100644
--- a/src/util/allocators/stdalloc.c
+++ b/src/util/allocators/stdalloc.c
@@ -12,11 +12,6 @@ static void *stdalloc__malloc(size_t len, const char *file, int line)
 	GIT_UNUSED(file);
 	GIT_UNUSED(line);
 
-#ifdef GIT_DEBUG_STRICT_ALLOC
-	if (!len)
-		return NULL;
-#endif
-
 	return malloc(len);
 }
 
@@ -25,11 +20,6 @@ static void *stdalloc__realloc(void *ptr, size_t size, const char *file, int lin
 	GIT_UNUSED(file);
 	GIT_UNUSED(line);
 
-#ifdef GIT_DEBUG_STRICT_ALLOC
-	if (!size)
-		return NULL;
-#endif
-
 	return realloc(ptr, size);
 }
 
diff --git a/src/util/unix/realpath.c b/src/util/unix/realpath.c
index 9e31a63b9..e1d2adb8d 100644
--- a/src/util/unix/realpath.c
+++ b/src/util/unix/realpath.c
@@ -16,17 +16,35 @@
 
 char *p_realpath(const char *pathname, char *resolved)
 {
-	char *ret;
-	if ((ret = realpath(pathname, resolved)) == NULL)
+	char *result;
+
+	if ((result = realpath(pathname, resolved)) == NULL)
 		return NULL;
 
 #ifdef __OpenBSD__
 	/* The OpenBSD realpath function behaves differently,
 	 * figure out if the file exists */
-	if (access(ret, F_OK) < 0)
-		ret = NULL;
+	if (access(ret, F_OK) < 0) {
+		if (!resolved)
+			free(result);
+
+		return NULL;
+	}
 #endif
-	return ret;
+
+	/*
+	 * If resolved == NULL, the system has allocated the result
+	 * string. We need to strdup this into _our_ allocator pool
+	 * so that callers can free it with git__free.
+	 */
+	if (!resolved) {
+		char *dup = git__strdup(result);
+		free(result);
+
+		result = dup;
+	}
+
+	return result;
 }
 
 #endif
diff --git a/tests/clar/clar_libgit2_alloc.c b/tests/clar/clar_libgit2_alloc.c
index e93037923..54eacd543 100644
--- a/tests/clar/clar_libgit2_alloc.c
+++ b/tests/clar/clar_libgit2_alloc.c
@@ -104,7 +104,5 @@ void cl_alloc_limit(size_t bytes)
 
 void cl_alloc_reset(void)
 {
-	git_allocator stdalloc;
-	git_stdalloc_init_allocator(&stdalloc);
-	git_allocator_setup(&stdalloc);
+	git_allocator_setup(NULL);
 }
diff --git a/tests/libgit2/checkout/conflict.c b/tests/libgit2/checkout/conflict.c
index b2eb939dc..3539c8b2d 100644
--- a/tests/libgit2/checkout/conflict.c
+++ b/tests/libgit2/checkout/conflict.c
@@ -1095,7 +1095,7 @@ static void collect_progress(
 	if (path == NULL)
 		return;
 
-	git_vector_insert(paths, strdup(path));
+	git_vector_insert(paths, git__strdup(path));
 }
 
 void test_checkout_conflict__report_progress(void)
diff --git a/tests/libgit2/checkout/icase.c b/tests/libgit2/checkout/icase.c
index d77c7abd5..3769a9f9b 100644
--- a/tests/libgit2/checkout/icase.c
+++ b/tests/libgit2/checkout/icase.c
@@ -89,7 +89,7 @@ static void assert_name_is(const char *expected)
 	if (start)
 		cl_assert_equal_strn("/", actual + (start - 1), 1);
 
-	free(actual);
+	git__free(actual);
 }
 
 static int symlink_or_fake(git_repository *repo, const char *a, const char *b)
diff --git a/tests/libgit2/remote/fetch.c b/tests/libgit2/remote/fetch.c
index a5d3272c5..7d2d11e27 100644
--- a/tests/libgit2/remote/fetch.c
+++ b/tests/libgit2/remote/fetch.c
@@ -40,10 +40,10 @@ void test_remote_fetch__cleanup(void) {
 	git_repository_free(repo2);
 
 	cl_git_pass(git_futils_rmdir_r(repo1_path, NULL, GIT_RMDIR_REMOVE_FILES));
-	free(repo1_path);
+	git__free(repo1_path);
 
 	cl_git_pass(git_futils_rmdir_r(repo2_path, NULL, GIT_RMDIR_REMOVE_FILES));
-	free(repo2_path);
+	git__free(repo2_path);
 }