Minor tweaks in startup_child(). Logic isn't changed (but code is)

* strace.c (startup_attach): Tweak comment.
(startup_child): Move common code out of ifdef.
Indent nested ifdefs. Tweak comments. Remove two
unnecessary calls to getpid().

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

diff --git a/strace.c b/strace.c
index bdc2112caddf164b6ff7c8d5eded79833e69ce5a..afb5d29e511281232601b661611c96e369271574 100644 (file)
--- a/strace.c
+++ b/strace.c
@@ -415,7 +415,7 @@ startup_attach(void)
        /*
         * Block user interruptions as we would leave the traced
         * process stopped (process state T) if we would terminate in
-        * between PTRACE_ATTACH and wait4 () on SIGSTOP.
+        * between PTRACE_ATTACH and wait4() on SIGSTOP.
         * We rely on cleanup() from this point on.
         */
        if (interactive)
@@ -628,24 +628,22 @@ startup_child(char **argv)
         || (pid == 0 && !daemonized_tracer) /* not -D: child to become a traced process */
        ) {
                pid = getpid();
+               if (outf != stderr)
+                       close(fileno(outf));
 #ifdef USE_PROCFS
-               if (outf != stderr) close(fileno(outf));
-#ifdef MIPS
+# ifdef MIPS
                /* Kludge for SGI, see proc_open for details. */
                sa.sa_handler = foobar;
                sa.sa_flags = 0;
                sigemptyset(&sa.sa_mask);
                sigaction(SIGINT, &sa, NULL);
-#endif /* MIPS */
-#ifndef FREEBSD
+# endif
+# ifndef FREEBSD
                pause();
-#else /* FREEBSD */
+# else
                kill(pid, SIGSTOP); /* stop HERE */
-#endif /* FREEBSD */
+# endif
 #else /* !USE_PROCFS */
-               if (outf != stderr)
-                       close(fileno(outf));
-
                if (!daemonized_tracer) {
                        if (ptrace(PTRACE_TRACEME, 0, (char *) 1, 0) < 0) {
                                perror_msg_and_die("ptrace(PTRACE_TRACEME, ...)");
@@ -684,14 +682,14 @@ startup_child(char **argv)
 
                if (!daemonized_tracer) {
                        /*
-                        * Induce an immediate stop so that the parent
+                        * Induce a ptrace stop. Tracer (our parent)
                         * will resume us with PTRACE_SYSCALL and display
-                        * this execve call normally.
-                        * Unless of course we're on a no-MMU system where
-                        * we vfork()-ed, so we cannot stop the child.
+                        * the immediately following execve syscall.
+                        * Can't do this on NOMMU systems, we are after
+                        * vfork: parent is blocked, stopping would deadlock.
                         */
                        if (!strace_vforked)
-                               kill(getpid(), SIGSTOP);
+                               kill(pid, SIGSTOP);
                } else {
                        struct sigaction sv_sigchld;
                        sigaction(SIGCHLD, NULL, &sv_sigchld);
@@ -715,20 +713,25 @@ startup_child(char **argv)
                perror_msg_and_die("exec");
        }
 
-       /* We are the tracer.  */
-       /* With -D, we are *child* here, IOW: different pid. Fetch it. */
-       strace_tracer_pid = getpid();
+       /* We are the tracer */
 
-       tcp = alloctcb(daemonized_tracer ? getppid() : pid);
-       if (daemonized_tracer) {
-               /* We want subsequent startup_attach() to attach to it.  */
+       if (!daemonized_tracer) {
+               tcp = alloctcb(pid);
+       }
+       else {
+               /* With -D, *we* are child here, IOW: different pid. Fetch it: */
+               strace_tracer_pid = getpid();
+               /* The tracee is our parent: */
+               pid = getppid();
+               tcp = alloctcb(pid);
+               /* We want subsequent startup_attach() to attach to it: */
                tcp->flags |= TCB_ATTACHED;
        }
 #ifdef USE_PROCFS
        if (proc_open(tcp, 0) < 0) {
                perror_msg_and_die("trouble opening proc file");
        }
-#endif /* USE_PROCFS */
+#endif
 }
 
 #ifdef LINUX