False positive with volatile variables in branch conditions

[Jeffrey Knockel]

Hello cppcheck community,

Using cppcheck 2.3, I found that cppcheck can generate a false positive (knownConditionTrueFalse) when a volatile variable is checked in a branch condition. Consider the following example:

#include <stdio.h>
#include <signal.h>

static volatile sig_atomic_t is_running;

static void handler(int signum) {
    is_running = 0;
}

int main(void) {
    signal(SIGINT, &handler);
    is_running = 1;
    while (is_running) {}
    printf("Interrupted!\n");
    return 0;
}

When run with the --enable=all option, cppcheck generates the following warning:

example.c:13:12: style: Condition 'is_running' is always true [knownConditionTrueFalse]
    while (is_running) {}
           ^

Thank you for your attention in this matter.

[Daniel Marjamäki]

Thanks! I can reproduce. I created https://trac.cppcheck.net/ticket/10223