CXX-W2009 @ ff6ee01 • MissouriMRDT / Autonomy

Run summary

4 days ago

d15cac6..ff6ee01

3 mins 14 s

Audit required: found a non-const global variable CXX-W2009

Anti-pattern

Minor

70 occurrences in this check

Found a non-const global variable 'bMainStop' which is prone to unpredictable changes

src/main.cpp

 24#endif
 25
 26// Create a boolean used to handle a SIGINT and exit gracefully.
 27volatile sig_atomic_t bMainStop = false; 28
 29/******************************************************************************
 30 * @brief Help function given to the C++ csignal standard library to run when

Found a non-const global variable 'bRunExampleFlag' which is prone to unpredictable changes

src/main.cpp

 16// If not included, define empty run example function and set bRunExampleFlag
 17// to false. If included, then define bRunExampleFlag as true.
 18#ifndef CHECK_IF_EXAMPLE_INCLUDED
 19static bool bRunExampleFlag = false; 20
 21void RunExample() {}
 22#else

Found a non-const global variable 'g_bRoveCommTCPStatus' which is prone to unpredictable changes

src/AutonomyNetworking.h

34
35    // RoveComm Status:
36    extern bool g_bRoveCommUDPStatus;
37    extern bool g_bRoveCommTCPStatus;38}    // namespace network
39
40#endif    // AUTONOMY_NETWORKING_H

Found a non-const global variable 'g_bRoveCommUDPStatus' which is prone to unpredictable changes

src/AutonomyNetworking.h

33    extern rovecomm::RoveCommTCP* g_pRoveCommTCPNode;    // Global RoveComm TCP Instance.
34
35    // RoveComm Status:
36    extern bool g_bRoveCommUDPStatus;37    extern bool g_bRoveCommTCPStatus;
38}    // namespace network
39

Found a non-const global variable 'g_pRoveCommTCPNode' which is prone to unpredictable changes

src/AutonomyNetworking.h

30{
31    // RoveComm Instances:
32    extern rovecomm::RoveCommUDP* g_pRoveCommUDPNode;    // Global RoveComm UDP Instance.
33    extern rovecomm::RoveCommTCP* g_pRoveCommTCPNode;    // Global RoveComm TCP Instance.34
35    // RoveComm Status:
36    extern bool g_bRoveCommUDPStatus;

Found a non-const global variable 'g_pRoveCommTCPNode' which is prone to unpredictable changes

src/AutonomyNetworking.h

30{
31    // RoveComm Instances:
32    extern rovecomm::RoveCommUDP* g_pRoveCommUDPNode;    // Global RoveComm UDP Instance.
33    extern rovecomm::RoveCommTCP* g_pRoveCommTCPNode;    // Global RoveComm TCP Instance.34
35    // RoveComm Status:
36    extern bool g_bRoveCommUDPStatus;

Found a non-const global variable 'g_pRoveCommUDPNode' which is prone to unpredictable changes

src/AutonomyNetworking.h

29namespace network
30{
31    // RoveComm Instances:
32    extern rovecomm::RoveCommUDP* g_pRoveCommUDPNode;    // Global RoveComm UDP Instance.33    extern rovecomm::RoveCommTCP* g_pRoveCommTCPNode;    // Global RoveComm TCP Instance.
34
35    // RoveComm Status:

Found a non-const global variable 'g_pRoveCommUDPNode' which is prone to unpredictable changes

src/AutonomyNetworking.h

29namespace network
30{
31    // RoveComm Instances:
32    extern rovecomm::RoveCommUDP* g_pRoveCommUDPNode;    // Global RoveComm UDP Instance.33    extern rovecomm::RoveCommTCP* g_pRoveCommTCPNode;    // Global RoveComm TCP Instance.
34
35    // RoveComm Status:

Found a non-const global variable 'g_bRoveCommTCPStatus' which is prone to unpredictable changes

src/AutonomyNetworking.cpp

37
38    // RoveComm Status:
39    bool g_bRoveCommUDPStatus = false;
40    bool g_bRoveCommTCPStatus = false;41}    // namespace network

Found a non-const global variable 'g_bRoveCommUDPStatus' which is prone to unpredictable changes

src/AutonomyNetworking.cpp

36    rovecomm::RoveCommTCP* g_pRoveCommTCPNode;
37
38    // RoveComm Status:
39    bool g_bRoveCommUDPStatus = false;40    bool g_bRoveCommTCPStatus = false;
41}    // namespace network

Found a non-const global variable 'g_pRoveCommTCPNode' which is prone to unpredictable changes

src/AutonomyNetworking.cpp

33{
34    // RoveComm Instances:
35    rovecomm::RoveCommUDP* g_pRoveCommUDPNode;
36    rovecomm::RoveCommTCP* g_pRoveCommTCPNode;37
38    // RoveComm Status:
39    bool g_bRoveCommUDPStatus = false;

Found a non-const global variable 'g_pRoveCommTCPNode' which is prone to unpredictable changes

src/AutonomyNetworking.cpp

33{
34    // RoveComm Instances:
35    rovecomm::RoveCommUDP* g_pRoveCommUDPNode;
36    rovecomm::RoveCommTCP* g_pRoveCommTCPNode;37
38    // RoveComm Status:
39    bool g_bRoveCommUDPStatus = false;

Found a non-const global variable 'g_pRoveCommUDPNode' which is prone to unpredictable changes

src/AutonomyNetworking.cpp

32namespace network
33{
34    // RoveComm Instances:
35    rovecomm::RoveCommUDP* g_pRoveCommUDPNode;36    rovecomm::RoveCommTCP* g_pRoveCommTCPNode;
37
38    // RoveComm Status:

Found a non-const global variable 'g_pRoveCommUDPNode' which is prone to unpredictable changes

src/AutonomyNetworking.cpp

32namespace network
33{
34    // RoveComm Instances:
35    rovecomm::RoveCommUDP* g_pRoveCommUDPNode;36    rovecomm::RoveCommTCP* g_pRoveCommTCPNode;
37
38    // RoveComm Status:

Found a non-const global variable 'g_szProgramStartTimeString' which is prone to unpredictable changes

src/AutonomyLogging.h

 80    extern quill::LogLevel g_eFileLogLevel;
 81    extern quill::LogLevel g_eRoveCommLogLevel;
 82
 83    extern std::string g_szProgramStartTimeString; 84
 85    /////////////////////////////////////////
 86    // Declare namespace methods.

Found a non-const global variable 'g_eRoveCommLogLevel' which is prone to unpredictable changes

src/AutonomyLogging.h

 78
 79    extern quill::LogLevel g_eConsoleLogLevel;
 80    extern quill::LogLevel g_eFileLogLevel;
 81    extern quill::LogLevel g_eRoveCommLogLevel; 82
 83    extern std::string g_szProgramStartTimeString;
 84

Found a non-const global variable 'g_eFileLogLevel' which is prone to unpredictable changes

src/AutonomyLogging.h

 77    extern quill::Logger* g_qRoveCommLogger;
 78
 79    extern quill::LogLevel g_eConsoleLogLevel;
 80    extern quill::LogLevel g_eFileLogLevel; 81    extern quill::LogLevel g_eRoveCommLogLevel;
 82
 83    extern std::string g_szProgramStartTimeString;

Found a non-const global variable 'g_eConsoleLogLevel' which is prone to unpredictable changes

src/AutonomyLogging.h

 76    extern quill::Logger* g_qSharedLogger;
 77    extern quill::Logger* g_qRoveCommLogger;
 78
 79    extern quill::LogLevel g_eConsoleLogLevel; 80    extern quill::LogLevel g_eFileLogLevel;
 81    extern quill::LogLevel g_eRoveCommLogLevel;
 82

Found a non-const global variable 'g_qRoveCommLogger' which is prone to unpredictable changes

src/AutonomyLogging.h

 74    extern quill::Logger* g_qFileLogger;
 75    extern quill::Logger* g_qConsoleLogger;
 76    extern quill::Logger* g_qSharedLogger;
 77    extern quill::Logger* g_qRoveCommLogger; 78
 79    extern quill::LogLevel g_eConsoleLogLevel;
 80    extern quill::LogLevel g_eFileLogLevel;

Found a non-const global variable 'g_qRoveCommLogger' which is prone to unpredictable changes

src/AutonomyLogging.h

 74    extern quill::Logger* g_qFileLogger;
 75    extern quill::Logger* g_qConsoleLogger;
 76    extern quill::Logger* g_qSharedLogger;
 77    extern quill::Logger* g_qRoveCommLogger; 78
 79    extern quill::LogLevel g_eConsoleLogLevel;
 80    extern quill::LogLevel g_eFileLogLevel;

Found a non-const global variable 'g_qSharedLogger' which is prone to unpredictable changes

src/AutonomyLogging.h

 73
 74    extern quill::Logger* g_qFileLogger;
 75    extern quill::Logger* g_qConsoleLogger;
 76    extern quill::Logger* g_qSharedLogger; 77    extern quill::Logger* g_qRoveCommLogger;
 78
 79    extern quill::LogLevel g_eConsoleLogLevel;

Found a non-const global variable 'g_qSharedLogger' which is prone to unpredictable changes

src/AutonomyLogging.h

 73
 74    extern quill::Logger* g_qFileLogger;
 75    extern quill::Logger* g_qConsoleLogger;
 76    extern quill::Logger* g_qSharedLogger; 77    extern quill::Logger* g_qRoveCommLogger;
 78
 79    extern quill::LogLevel g_eConsoleLogLevel;

Found a non-const global variable 'g_qConsoleLogger' which is prone to unpredictable changes

src/AutonomyLogging.h

 72    /////////////////////////////////////////
 73
 74    extern quill::Logger* g_qFileLogger;
 75    extern quill::Logger* g_qConsoleLogger; 76    extern quill::Logger* g_qSharedLogger;
 77    extern quill::Logger* g_qRoveCommLogger;
 78

Found a non-const global variable 'g_qConsoleLogger' which is prone to unpredictable changes

src/AutonomyLogging.h

 72    /////////////////////////////////////////
 73
 74    extern quill::Logger* g_qFileLogger;
 75    extern quill::Logger* g_qConsoleLogger; 76    extern quill::Logger* g_qSharedLogger;
 77    extern quill::Logger* g_qRoveCommLogger;
 78

Found a non-const global variable 'g_qFileLogger' which is prone to unpredictable changes

src/AutonomyLogging.h

 71    // Declare namespace external variables and objects.
 72    /////////////////////////////////////////
 73
 74    extern quill::Logger* g_qFileLogger; 75    extern quill::Logger* g_qConsoleLogger;
 76    extern quill::Logger* g_qSharedLogger;
 77    extern quill::Logger* g_qRoveCommLogger;

Description

Global variables are accessible anywhere in the scope of the program even in the threads outside of the main thread, as long as it shares the main process stack.

A mutable global variable have high dependency and the dependent code on such variables have no way to learn about the changes to the variable. Hence using a non-const global variables is considered quite risky, as they can lead to data races or contention issues.

Consider avoiding the use of global variable by adding a qualifier const. If the variable must be mutable then consider passing the variable as argument to the functions which are designed to mutate the variable.

In the case of atomic or synchronization primitives being used to handle data races, there is still concern about misuse, which can be reduced by making it non-global. That is a private class member that can only be used by its function.

Consider passing references to unique values and then merging them as if you need mutable stack of program memory.

Note that const pointers and pointer to const are not the same. You need a global pointer to be entirely const for this lint to be satisfied.

That is, if you are passing a pointer, then you need to make sure that the pointer is a const pointer to a const. (See here for more information.)

const int *p = &x;
// should instead be
const int *const p = &x;

Bad practice

std::atomic<bool> flag(false);

int global_counter = 0;
void foo() {
    global_counter += 1;
    flag.store(true);
}

int main() {
    global_counter += 1;
    std::thread t(foo);
    flag.store(false); // there won't be a data race,
    // but the output can still be unexpected as we
    // don't know which mutation will occur last
    t.join();
}

#include <thread>

int main() {
    int global_counter = 1;
    int global_counter1 = 0;
    std::atomic<bool> flag(false);
    std::thread t1([&](){
        for (int i = 0; i < 10; i++) {
            global_counter1 += 1;
            flag.store(true);
        }
    });
    int global_counter2 = 0;
    std::thread t2([&](){
        for (int i = 0; i < 10; i++) {
            global_counter2 += 1;
            flag.store(false);
        }
    });
    t1.join();
    t2.join();
    // we again don't know which one executed
    // last but we know nothing else but things
    // from this scope can use it making
    // debugging easier
    global_counter += global_counter1 + global_counter2;
}

MissouriMRDT / Autonomy_Software

Bad practice

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References