perf: init debug_print_buffer in run_polyjuice()

All the elements of global arrays are initialized to default values
(zero for arithmetic types and NULL for pointers).
`memset` caused by the initialization of such arrays is not necessary.

c/polyjuice.h

@@ -1154,6 +1154,12 @@ int clean_evmc_result_and_return(evmc_result *res, int code) {
 }
 
 int run_polyjuice() {
+#ifndef NO_DEBUG_LOG
+  // init buffer for debug_print
+  char buffer[DEBUG_BUFFER_SIZE];
+  debug_buffer = buffer;
+#endif
+
   int ret;
 
   /* prepare context */

c/polyjuice_utils.h

@@ -15,17 +15,23 @@
 #define debug_print(s) {}
 #define debug_print_int(prefix, value) {}
 #define debug_print_data(prefix, data, data_len) {}
-#else  /* #ifdef NO_DEBUG_LOG */
-static char debug_buffer[64 * 1024];
+#else /* NO_DEBUG_LOG */
+/* 64 KB */
+#define DEBUG_BUFFER_SIZE 65536
+static char *debug_buffer;
 void debug_print_data(const char *prefix, const uint8_t *data,
                       uint32_t data_len) {
-  if (data_len > 31 * 1024) {
-    ckb_debug("warning: print_data is too large");
+  if (data_len > (DEBUG_BUFFER_SIZE - 1024) / 2 - 1) { // leave 1KB to prefix
+    ckb_debug("warning: length of data is too large");
     return;
   }
 
   int offset = 0;
   offset += sprintf(debug_buffer, "%s 0x", prefix);
+  if (offset > 1024) {
+    ckb_debug("warning: length of prefix is too large");
+    return;
+  }
   for (size_t i = 0; i < data_len; i++) {
     offset += sprintf(debug_buffer + offset, "%02x", data[i]);
   }
@@ -36,7 +42,7 @@ void debug_print_int(const char* prefix, int64_t ret) {
   sprintf(debug_buffer, "%s => %ld", prefix, ret);
   ckb_debug(debug_buffer);
 }
-#endif  /* #ifdef NO_DEBUG_LOG */
+#endif /* NO_DEBUG_LOG */
 
 /* polyjuice contract account (normal/create2) script args size*/
 static const uint32_t CONTRACT_ACCOUNT_SCRIPT_ARGS_SIZE = 32 + 4 + 20;

c/tests/test_contracts.c

@@ -632,6 +632,12 @@ int init_mock_state() {
 #endif
 
 int main() {
+#ifndef NO_DEBUG_LOG
+  // init buffer for debug_print
+  char buffer[DEBUG_BUFFER_SIZE];
+  debug_buffer = buffer;
+#endif
+
 #ifdef FUZZING
   if (0 != init_mock_state()) {
     ckb_debug("[init_mock_state] failed to init_mock_state");

c/tests/test_rlp.c

@@ -58,6 +58,12 @@ void test(const char *sender_hex, uint32_t nonce, const char *expected_rlp, cons
 }
 
 int main() {
+#ifndef NO_DEBUG_LOG
+  // init buffer for debug_print
+  char buffer[DEBUG_BUFFER_SIZE];
+  debug_buffer = buffer;
+#endif
+
   test("004ec07d2329997267ec62b4166639513386f32e", 142, "d794004ec07d2329997267ec62b4166639513386f32e818e", "8d7bb25141ff9c4c77e9e208b6bf4d1d3ca684b0");
   test("004ec07d2329997267ec62b4166639513386f32e", 512, "d894004ec07d2329997267ec62b4166639513386f32e820200", "ecf98cb7016edb8e306e844a420597770de4e555");
   test("004ec07d2329997267ec62b4166639513386f32e", 1111, "d894004ec07d2329997267ec62b4166639513386f32e820457", "e2be2e38fc6dc1eed5cab7e5af984c8ebb8c0854");