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// based on http://stackoverflow.com/questions/4636456/stack-trace-for-c-using-gcc/4732119#4732119
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <unistd.h>
#include <signal.h>
extern int done;
extern int emcOperatorError(int id, const char *fmt, ...);
extern int emcOperatorText(int id, const char *fmt, ...);
void backtrace(int signo)
{
char pid_buf[30];
char name_buf[512];
char filename[512];
signal(signo, SIG_IGN); // prevent multiple invocations on same signal
sprintf(pid_buf, "%d", getpid());
sprintf(filename,"/tmp/backtrace.%s", pid_buf);
name_buf[readlink("/proc/self/exe", name_buf, 511)]=0;
int child_pid = fork();
if (!child_pid) {
fclose(stderr);
stderr = freopen(filename, "a", stderr);
dup2(2,1); // child: redirect output to stderr
fprintf(stdout,"stack trace for %s pid=%s signal=%d\n",name_buf,pid_buf, signo);
execlp("gdb", "gdb", "--batch", "-n", "-ex", "thread", "-ex", "bt", name_buf, pid_buf, NULL);
emcOperatorError(0, "backtrace for %s (pid %s signal %d): gdb failed to start", name_buf, pid_buf, signo);
abort(); /* If gdb failed to start */
} else {
int status;
waitpid(child_pid, &status,0);
if (signo == SIGUSR1) { // continue running after backtrace
signal(SIGUSR1, backtrace);
emcOperatorText(0, "backtrace for %s stored in %s, continuing", name_buf, filename);
fprintf(stderr, "%s: backtrace stored in %s, continuing\n", name_buf, filename);
} else {
// this takes emcmodule.cc:EMC_COMMAND_TIMEOUT seconds to display:
if (status == 0) // backtrace succeeded
emcOperatorError(0, "%s (pid %d) died on signal %d, backtrace stored in %s",
name_buf, getpid(), signo, filename);
fprintf(stderr, "%s exiting\n", name_buf);
done = 1; // signal task to exit main loop
}
}
}
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