pre_check.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/ptrace.h>

void pre_check(int argc, char **argv, char **envp)
{
    printf("Inside pre_check!\n");
    if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0)
    {
        printf("Aliens found!\n");
        exit(0);
    }
}

__attribute__((section(".preinit_array"))) typeof(pre_check) *_preinit = pre_check;
void __attribute__ ((constructor)) anti_trace(void);

void anti_trace(void)
{
    printf("Inside constructor!\n");
}

void message()
{
    printf("Last place, called from main() :(\n");
}

int main(int argc, char **argv)
{
    message();
    return 0;
}