Slight optimization and cleanup in trace()

* strace.c (trace): Do not recalculate "cflag ? &ru : NULL"
again and again. Do not clear errno unnecessarily.
Consistently check wait errors as pid < 0, not pid == -1.
Indent ifdefs for better readability.
Remove comments after endif if ifdef/endif block is really tiny.

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

diff --git a/strace.c b/strace.c
index df10a723e31229468f33b049a705bdabf5a32a45..dd179c9576c99160845dca55856cdf9949186465 100644 (file)
--- a/strace.c
+++ b/strace.c
@@ -2351,9 +2351,10 @@ trace()
        struct tcb *tcp;
 #ifdef LINUX
        struct rusage ru;
-#ifdef __WALL
+       struct rusage *rup = cflag ? &ru : NULL;
+# ifdef __WALL
        static int wait4_options = __WALL;
-#endif
+# endif
 #endif /* LINUX */
 
        while (nprocs != 0) {
@@ -2362,35 +2363,32 @@ trace()
                if (interactive)
                        sigprocmask(SIG_SETMASK, &empty_set, NULL);
 #ifdef LINUX
-#ifdef __WALL
-               pid = wait4(-1, &status, wait4_options, cflag ? &ru : NULL);
+# ifdef __WALL
+               pid = wait4(-1, &status, wait4_options, rup);
                if (pid < 0 && (wait4_options & __WALL) && errno == EINVAL) {
                        /* this kernel does not support __WALL */
                        wait4_options &= ~__WALL;
-                       errno = 0;
-                       pid = wait4(-1, &status, wait4_options,
-                                       cflag ? &ru : NULL);
+                       pid = wait4(-1, &status, wait4_options, rup);
                }
                if (pid < 0 && !(wait4_options & __WALL) && errno == ECHILD) {
                        /* most likely a "cloned" process */
-                       pid = wait4(-1, &status, __WCLONE,
-                                       cflag ? &ru : NULL);
-                       if (pid == -1) {
+                       pid = wait4(-1, &status, __WCLONE, rup);
+                       if (pid < 0) {
                                perror_msg("wait4(__WCLONE) failed");
                        }
                }
-#else
-               pid = wait4(-1, &status, 0, cflag ? &ru : NULL);
-#endif /* __WALL */
+# else
+               pid = wait4(-1, &status, 0, rup);
+# endif /* __WALL */
 #endif /* LINUX */
 #ifdef SUNOS4
                pid = wait(&status);
-#endif /* SUNOS4 */
+#endif
                wait_errno = errno;
                if (interactive)
                        sigprocmask(SIG_BLOCK, &blocked_set, NULL);
 
-               if (pid == -1) {
+               if (pid < 0) {
                        switch (wait_errno) {
                        case EINTR:
                                continue;