1 files changed, 106 insertions, 0 deletions
diff --git a/tests/clar/clar_libgit2_alloc.c b/tests/clar/clar_libgit2_alloc.c
new file mode 100644
index 000000000..7abc998ce
--- /dev/null
+++ b/tests/clar/clar_libgit2_alloc.c
@@ -0,0 +1,106 @@
+/*
+ * 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 "clar_libgit2_alloc.h"
+
+static size_t bytes_available;
+
+/*
+ * The clar allocator uses a tagging mechanism for pointers that
+ * prepends the actual pointer's number bytes as `size_t`.
+ *
+ * First, this is required in order to be able to implement
+ * proper bookkeeping of allocated bytes in both `free` and
+ * `realloc`.
+ *
+ * Second, it may also be able to spot bugs that are
+ * otherwise hard to grasp, as the returned pointer cannot be
+ * free'd directly via free(3P). Instead, one is forced to use
+ * the tandem of `cl__malloc` and `cl__free`, as otherwise the
+ * code is going to crash hard. This is considered to be a
+ * feature, as it helps e.g. in finding cases where by accident
+ * malloc(3P) and free(3P) were used instead of git__malloc and
+ * git__free, respectively.
+ *
+ * The downside is obviously that each allocation grows by
+ * sizeof(size_t) bytes. As the allocator is for testing purposes
+ * only, this tradeoff is considered to be perfectly fine,
+ * though.
+ */
+
+static void *cl__malloc(size_t len, const char *file, int line)
+{
+	char *ptr = NULL;
+	size_t alloclen;
+
+	GIT_UNUSED(file);
+	GIT_UNUSED(line);
+
+	if (len > bytes_available)
+		goto out;
+
+	if (GIT_ADD_SIZET_OVERFLOW(&alloclen, len, sizeof(size_t)) ||
+	    (ptr = malloc(alloclen)) == NULL)
+		goto out;
+	memcpy(ptr, &len, sizeof(size_t));
+
+	bytes_available -= len;
+
+out:
+	return ptr ? ptr + sizeof(size_t) : NULL;
+}
+
+static void cl__free(void *ptr)
+{
+	if (ptr) {
+		char *p = ptr;
+		size_t len;
+		memcpy(&len, p - sizeof(size_t), sizeof(size_t));
+		free(p - sizeof(size_t));
+		bytes_available += len;
+	}
+}
+
+static void *cl__realloc(void *ptr, size_t size, const char *file, int line)
+{
+	size_t copybytes = 0;
+	char *p = ptr;
+	void *new;
+
+	if (p)
+		memcpy(&copybytes, p - sizeof(size_t), sizeof(size_t));
+	if (copybytes > size)
+		copybytes = size;
+
+	if ((new = cl__malloc(size, file, line)) == NULL)
+		goto out;
+	memcpy(new, p, copybytes);
+	cl__free(p);
+
+out:
+	return new;
+}
+
+void cl_alloc_limit(size_t bytes)
+{
+	git_allocator alloc;
+
+	alloc.gmalloc = cl__malloc;
+	alloc.grealloc = cl__realloc;
+	alloc.gfree = cl__free;
+
+	git_allocator_setup(&alloc);
+
+	bytes_available = bytes;
+}
+
+void cl_alloc_reset(void)
+{
+	git_allocator stdalloc;
+	git_stdalloc_init_allocator(&stdalloc);
+	git_allocator_setup(&stdalloc);
+}