Originally posted by: Manolo123

Hello everyone!

I am currently developing an application on IBM Power 5+ system with AIX installed, here is the oslevel -g:

Fileset                                 Actual Level        Maintenance Level ----------------------------------------------------------------------------- bos.rte                                 5.3.11.0            5.3.0.0

I am using ptrace to trace the execution of the child process. Whenever the child stops, a SIGCHLD is sent to the parent, but the si_code part of siginfo_t always has the value of 8, which is SI_UNDEFINED. Here is my program:

#include <sys/user.h> #include <sys/reg.h> #include <sys/ldr.h> #include <string.h>   #include <cstdlib> #include <iostream>   using namespace std;   

void sigchld_act(

int signo, siginfo_t *si, 

void *v) 
{ cout << 
"Signo: " << signo << endl; cout << 
"si->code: " << si->si_code << endl; 
}     

int main(

int argc, char** argv) 
{   struct sigaction old; struct sigaction act; act.sa_sigaction = sigchld_act; act.sa_flags = SA_SIGINFO; sigemptyset(&act.sa_mask); sigaddset(&act.sa_mask, SIGCHLD);   

if (sigaction(SIGCHLD, &act, &old) < 0) 
{ cout << 
"SignalHandler:Sigaction SIGCHLD failed." << endl; 

return 

false; 
}     pid_t child = fork(); 

if (child < 0) 
{ perror(
"Fork failed\n"); 
} 

else 

if (child == 0) 
{ ptrace(PT_TRACE_ME, 0, 0, 0, 0); execvp(argv[1], &argv[1]); 
} 

else 
{ 

while (1) 
{ 

int status; wait(&status); 

if (WIFEXITED(status)) 
{ cout << 
"Child exited" << endl; 

break; 
} ptrace(PT_CONTINUE, child, (int*) 1, 0, NULL); 
} 
} 
}

And the result is:

Signo: 20 si->code: 8 Ptrace --- Signo: 20 si->code: 10 Child exited

The SI_UNDEFINED happens always when the SIGCHLD is sent, except for the situation when the child has exited, in this case si_code is CLD_EXITED as expected. But when I am performing single stepping along the instructions (with ptrace ofcourse), it is always 8. Does anyone know a cure for it?
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