msgpack: fixed incorrect print of msgpack field

Due to the fact that we used `const char**` to save a pointer to the
original msgpack header, when restoring the pointer, we received an
incorrect value and as a consequence assertion failure later. Correctly
saving and restoring the pointer fixed this problem.

NO_DOC=bug fix
NO_CHANGELOG=bug fix

src/box/msgpack.c

@@ -40,7 +40,7 @@
 static int
 msgpack_fprint_ext(FILE *file, const char **data, int depth)
 {
-	const char **orig = data;
+	const char *orig = *data;
 	int8_t type;
 	uint32_t len = mp_decode_extl(data, &type);
 	switch(type) {
@@ -53,14 +53,15 @@ msgpack_fprint_ext(FILE *file, const char **data, int depth)
 	case MP_ERROR:
 		return mp_fprint_error(file, data, depth);
 	default:
-		return mp_fprint_ext_default(file, orig, depth);
+		*data = orig;
+		return mp_fprint_ext_default(file, data, depth);
 	}
 }
 
 static int
 msgpack_snprint_ext(char *buf, int size, const char **data, int depth)
 {
-	const char **orig = data;
+	const char *orig = *data;
 	int8_t type;
 	uint32_t len = mp_decode_extl(data, &type);
 	switch(type) {
@@ -73,7 +74,8 @@ msgpack_snprint_ext(char *buf, int size, const char **data, int depth)
 	case MP_ERROR:
 		return mp_snprint_error(buf, size, data, depth);
 	default:
-		return mp_snprint_ext_default(buf, size, orig, depth);
+		*data = orig;
+		return mp_snprint_ext_default(buf, size, data, depth);
 	}
 }
 

test/unit/CMakeLists.txt

@@ -140,6 +140,9 @@ if (ENABLE_BUNDLED_MSGPUCK)
     target_link_libraries(msgpack.test ${MSGPUCK_LIBRARIES})
 endif ()
 
+add_executable(mp_print_unknown_ext.test mp_print_unknown_ext.c)
+target_link_libraries(mp_print_unknown_ext.test unit box core)
+
 add_executable(scramble.test scramble.c core_test_utils.c)
 target_link_libraries(scramble.test scramble)
 

test/unit/mp_print_unknown_ext.c

+#include "msgpack.h"
+#include "mp_extension_types.h"
+
+#include "trivia/util.h"
+#include "unit.h"
+#include <stdio.h>
+
+static int
+test_mp_print(const char *sample, const char *ext_data)
+{
+	plan(2);
+
+	char str[200] = {0};
+
+	mp_snprint(str, sizeof(str), ext_data);
+	is(strcmp(sample, str), 0, "mp_snprint unknown extension");
+
+	memset(str, 0, sizeof(str));
+	FILE *f  = tmpfile();
+	assert(f != NULL);
+	mp_fprint(f, ext_data);
+	rewind(f);
+	fread(str, 1, sizeof(str), f);
+	is(strcmp(sample, str), 0, "mp_fprint unknown extension");
+
+	return check_plan();
+}
+
+static int
+test_mp_print_unknown_extention(void)
+{
+	plan(1);
+
+	char sample[] = "(extension: type 0, len 10)";
+	char data[] = { 0xca, 0xca, 0xca, 0xca, 0xca, 0xca, 0xca, 0xca, 0xca, 0xca };
+	char *ext_data = xmalloc(mp_sizeof_ext(sizeof(data)));
+
+	char *data_end = ext_data;
+	data_end = mp_encode_ext(data_end, MP_UNKNOWN_EXTENSION, data, sizeof(data));
+
+	test_mp_print(sample, ext_data);
+
+	free(ext_data);
+
+	return check_plan();
+}
+
+int
+main(void)
+{
+	plan(1);
+
+	msgpack_init();
+
+	test_mp_print_unknown_extention();
+
+	return check_plan();
+}

test/unit/mp_print_unknown_ext.result

+1..1
+    1..1
+        1..2
+        ok 1 - mp_snprint unknown extension
+        ok 2 - mp_fprint unknown extension
+    ok 1 - subtests
+ok 1 - subtests