Admitting Ignorance (AI)

I have to admit after researching "-ansi -D_GNU_SOURCE" and the definition "REG_RIP" and some searching through many headers, and dependencies, I still don't get it. It works, it works consistently, is does not fault. However, I have no sense of the complete picture. I have become entangled by the IFS, IFDEFS, #if defined, #if else, whiles and fors. I think I understand it and I hope that it will become clear the next time I visit this code, but as it sits, I wouldn't sign a statement that it would continue to work tomorrow. It works like I think it should, and I did write an extension to this code. The problem is that I am flying blind. I don't have a sense of the complete operation and I just code and then burn some incense, then chant OM, and then I spit over my left shoulder and compile. If it doesn't warn, I use it.

#if defined(SIGSEGV_STACK_X86) || defined(SIGSEGV_STACK_IA64)
 # if defined(SIGSEGV_STACK_IA64)
 ip = (void*)ucontext->uc_mcontext.gregs[REG_RIP];
 bp = (void**)ucontext->uc_mcontext.gregs[REG_RBP];
 # elif defined(SIGSEGV_STACK_X86)
 ip = (void*)ucontext->uc_mcontext.gregs[REG_EIP];
 bp = (void**)ucontext->uc_mcontext.gregs[REG_EBP];
 # endif
fprintf(stderr, "Stack trace:\n");
    while(bp && ip) {
        if(!dladdr(ip, &dlinfo)){break;}
symname = dlinfo.dli_sname;
 fprintf(stderr, "% 2d: %p <%s+%u> (%s)\n",++f,ip
 ,symname
 ,(unsigned int)((long unsigned int)ip - (long unsigned int)dlinfo.dli_saddr)
 ,dlinfo.dli_fname);
 if(dlinfo.dli_sname && !strcmp(dlinfo.dli_sname, "main")){break;}
 ip = bp[1];
 bp = (void**)bp[0];
    }
#ifdef EXTENSIVE2
    sz = backtrace(bt, 20);
    strings = backtrace_symbols(bt, sz);
 for (i=0; i < sz; i++) {
  if ( bt[i] < (void *)0x420000 && bt[i] > (void *)0x400000) {
  sprintf(syscom,"addr2line %p -f -e solver",bt[i]);
  system(syscom);}
 }
#endif