Add custom memory allocation

Thanks to Basile Starynkevitch for the suggestion and initial patch.
Thanks to Jonathan Landis and Deron Meranda for showing how this can
be utilized for implementing secure memory operations.

test/.gitignore

@@ -1,13 +1,14 @@
 logs
 bin/json_process
 suites/api/test_array
-suites/api/test_equal
 suites/api/test_copy
+suites/api/test_cpp
 suites/api/test_dump
+suites/api/test_equal
 suites/api/test_load
+suites/api/test_memory_funcs
 suites/api/test_number
 suites/api/test_object
-suites/api/test_simple
-suites/api/test_cpp
 suites/api/test_pack
+suites/api/test_simple
 suites/api/test_unpack

test/suites/api/Makefile.am

@@ -2,24 +2,26 @@ EXTRA_DIST = run
 
 check_PROGRAMS = \
 	test_array \
-	test_equal \
 	test_copy \
 	test_dump \
+	test_equal \
 	test_load \
-	test_simple \
+	test_memory_funcs \
 	test_number \
 	test_object \
 	test_pack \
+	test_simple \
 	test_unpack
 
 test_array_SOURCES = test_array.c util.h
 test_copy_SOURCES = test_copy.c util.h
 test_dump_SOURCES = test_dump.c util.h
 test_load_SOURCES = test_load.c util.h
-test_simple_SOURCES = test_simple.c util.h
+test_memory_funcs_SOURCES = test_memory_funcs.c util.h
 test_number_SOURCES = test_number.c util.h
 test_object_SOURCES = test_object.c util.h
 test_pack_SOURCES = test_pack.c util.h
+test_simple_SOURCES = test_simple.c util.h
 test_unpack_SOURCES = test_unpack.c util.h
 
 AM_CPPFLAGS = -I$(top_srcdir)/src

test/suites/api/check-exports

@@ -59,6 +59,7 @@ json_vpack_ex
 json_unpack
 json_unpack_ex
 json_vunpack_ex
+json_set_alloc_funcs
 EOF
 
 # The list of functions are not exported in the library because they

test/suites/api/test_memory_funcs.c

@@ -0,0 +1,84 @@
+#include <string.h>
+#include <jansson.h>
+
+#include "util.h"
+
+static int malloc_called = 0;
+static int free_called = 0;
+
+/* helper */
+static void create_and_free_complex_object()
+{
+    json_t *obj;
+
+    obj = json_pack("{s:i,s:n,s:b,s:b,s:{s:s},s:[i,i,i]",
+                    "foo", 42,
+                    "bar",
+                    "baz", 1,
+                    "qux", 0,
+                    "alice", "bar", "baz",
+                    "bob", 9, 8, 7);
+
+    json_decref(obj);
+}
+
+static void *my_malloc(size_t size)
+{
+    malloc_called += 1;
+    return malloc(size);
+}
+
+static void my_free(void *ptr)
+{
+    free_called += 1;
+    free(ptr);
+}
+
+static void test_simple()
+{
+    json_set_alloc_funcs(my_malloc, my_free);
+    create_and_free_complex_object();
+
+    if(malloc_called != 27 || free_called != 27)
+        fail("Custom allocation failed");
+}
+
+
+/*
+  Test the secure memory functions code given in the API reference
+  documentation, but by using plain memset instead of
+  guaranteed_memset().
+*/
+
+static void *secure_malloc(size_t size)
+{
+    /* Store the memory area size in the beginning of the block */
+    void *ptr = malloc(size + 8);
+    *((size_t *)ptr) = size;
+    return ptr + 8;
+}
+
+static void secure_free(void *ptr)
+{
+    size_t size;
+
+    ptr -= 8;
+    size = *((size_t *)ptr);
+
+    /*guaranteed_*/memset(ptr, 0, size);
+    free(ptr);
+}
+
+static void test_secure_funcs(void)
+{
+    json_set_alloc_funcs(secure_malloc, secure_free);
+    create_and_free_complex_object();
+}
+
+int main()
+{
+    test_simple();
+    test_secure_funcs();
+
+    return 0;
+}