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In this noncompliant code example, the program allocates a string on the heap and uses it to log messages in a loop. The program also registers the signal handler int_handler() to handle the terminal interrupt signal SIGINT. The int_handler() function logs the last message, calls free(), and exits.
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#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
enum { MAXLINE = 1024 };
char *info = NULL;
void log_message(void) {
fprintf(stderr, info);
}
void handler(int signum) {
log_message();
free(info);
info = NULL;
}
int main(void) {
if (signal(SIGINT, handler) == SIG_ERR) {
/* Handle error */
}
info = (char*)malloc(MAXLINE);
if (info == NULL) {
/* Handle Error */
}
while (1) {
/* Main loop program code */
log_message();
/* More program code */
}
return 0;
}
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This example code achieves compliance with this rule by moving the final log message and call to free() outside the signal handler.
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#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
enum { MAXLINE = 1024 };
volatile sig_atomic_t eflag = 0;
char *info = NULL;
void log_message(void) {
fprintf(stderr, info);
}
void handler(int signum) {
eflag = 1;
}
int main(void) {
if (signal(SIGINT, handler) == SIG_ERR) {
/* Handle error */
}
info = (char*)malloc(MAXLINE);
if (info == NULL) {
/* Handle error */
}
while (!eflag) {
/* Main loop program code */
log_message();
/* More program code */
}
log_message();
free(info);
info = NULL;
return 0;
}
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