[redisCommand]: Not store the error return code of redisFormat (#809)

In the previous implementation, the private member variable, len, will store the error code of redisFormat. This PR is for fixing that if the redisFormat raise an unexpected error code, the `len` will be assigned to zero.

common/rediscommand.cpp

@@ -25,16 +25,18 @@ void RedisCommand::format(const char *fmt, ...)
         redisFreeCommand(temp);
         temp = nullptr;
     }
+    len = 0;
 
     va_list ap;
     va_start(ap, fmt);
-    len = redisvFormatCommand(&temp, fmt, ap);
+    int ret = redisvFormatCommand(&temp, fmt, ap);
     va_end(ap);
-    if (len == -1) {
+    if (ret == -1) {
         throw std::bad_alloc();
-    } else if (len == -2) {
+    } else if (ret == -2) {
         throw std::invalid_argument("fmt");
     }
+    len = ret;
 }
 
 void RedisCommand::formatArgv(int argc, const char **argv, const size_t *argvlen)
@@ -44,11 +46,13 @@ void RedisCommand::formatArgv(int argc, const char **argv, const size_t *argvlen
         redisFreeCommand(temp);
         temp = nullptr;
     }
+    len = 0;
 
-    len = redisFormatCommandArgv(&temp, argc, argv, argvlen);
-    if (len == -1) {
+    int ret = redisFormatCommandArgv(&temp, argc, argv, argvlen);
+    if (ret == -1) {
         throw std::bad_alloc();
     }
+    len = ret;
 }
 
 void RedisCommand::format(const vector<string> &commands)
@@ -135,6 +139,8 @@ std::string RedisCommand::toPrintableString() const
 
 const char *RedisCommand::c_str() const
 {
+    if (len == 0)
+        return nullptr;
     return temp;
 }
 

tests/Makefile.am

@@ -5,6 +5,7 @@ LDADD_GTEST = -L/usr/src/gtest -lgtest -lgtest_main -lgmock -lgmock_main
 
 tests_tests_SOURCES = tests/redis_ut.cpp                \
                       tests/redis_piped_ut.cpp          \
+                      tests/redis_command_ut.cpp        \
                       tests/redis_state_ut.cpp          \
                       tests/redis_piped_state_ut.cpp    \
                       tests/tokenize_ut.cpp             \
@@ -44,5 +45,5 @@ tests_tests_SOURCES = tests/redis_ut.cpp                \
                       tests/main.cpp
 
 tests_tests_CFLAGS = $(DBGFLAGS) $(AM_CFLAGS) $(CFLAGS_COMMON) $(CFLAGS_GTEST) $(LIBNL_CFLAGS)
-tests_tests_CPPFLAGS = $(DBGFLAGS) $(AM_CFLAGS) $(CFLAGS_COMMON) $(CFLAGS_GTEST) $(LIBNL_CFLAGS)
+tests_tests_CPPFLAGS = $(DBGFLAGS) $(AM_CFLAGS) $(CFLAGS_COMMON) $(CFLAGS_GTEST) $(LIBNL_CFLAGS) -fno-access-control
 tests_tests_LDADD = $(LDADD_GTEST) -lpthread common/libswsscommon.la $(LIBNL_LIBS) $(CODE_COVERAGE_LIBS) sonic-db-cli/libsonicdbcli.la -lzmq -luuid -lboost_serialization

tests/redis_command_ut.cpp

@@ -0,0 +1,12 @@
+#include "gtest/gtest.h"
+#include "common/rediscommand.h"
+
+TEST(RedisCommand, invalid_redis_command)
+{
+    swss::RedisCommand cmd;
+    EXPECT_THROW(cmd.format("Invalid redis command %l^", 1), std::invalid_argument);
+    EXPECT_EQ(cmd.c_str(), nullptr);
+    EXPECT_EQ(cmd.length(), 0);
+    EXPECT_EQ(cmd.len, 0);
+    EXPECT_EQ(cmd.temp, nullptr);
+}