Fix PID prefix printing in "strace -oLOG -ff -p1 -p2 -p3" case

In this case we were printing PIDs to LOG.* files
even though it is not necessary.

The fix is in the addition of "&& followfork < 2" condition.

* strace.c: Remove pflag_seen variable, add print_pid_pfx one.
(process_opt_p_list): Do not pflag_seen++.
(main): Use "nprocs != 0" condition instead of "pflag_seen != 0".
Set print_pid_pfx before entering main tracing loop.
(printleader): Use print_pid_pfx to decide whether to print pid prefix.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/strace.c b/strace.c
index 5e2f9c6c27a6494b1b4edf116e0b0e20a577cf4d..e627a5ee88289c9bce7dbab7b944186ee38c6aea 100644 (file)
--- a/strace.c
+++ b/strace.c
@@ -72,7 +72,8 @@ unsigned int ptrace_setoptions = 0;
 static unsigned int syscall_trap_sig = SIGTRAP;
 int dtime = 0, xflag = 0, qflag = 0;
 cflag_t cflag = CFLAG_NONE;
-static int iflag = 0, pflag_seen = 0, rflag = 0, tflag = 0;
+static int iflag = 0, rflag = 0, tflag = 0;
+static int print_pid_pfx = 0;
 
 /* -I n */
 enum {
@@ -447,12 +448,6 @@ static void process_opt_p_list(char *opt)
                *delim = c;
                tcp = alloc_tcb(pid, 0);
                tcp->flags |= TCB_ATTACHED;
-               /*
-                * pflag_seen says how many PIDs we handled,
-                * not how many -p opts there were.
-                * Used to decide whether to print pid prefix in logs.
-                */
-               pflag_seen++;
                if (c == '\0')
                        break;
                opt = delim + 1;
@@ -1210,10 +1205,10 @@ main(int argc, char *argv[])
        acolumn_spaces[acolumn] = '\0';
 
        /* Must have PROG [ARGS], or -p PID. Not both. */
-       if (!argv[0] == !pflag_seen)
+       if (!argv[0] == !nprocs)
                usage(stderr, 1);
 
-       if (pflag_seen && daemonized_tracer) {
+       if (nprocs != 0 && daemonized_tracer) {
                error_msg_and_die("-D and -p are mutually exclusive options");
        }
 
@@ -1331,9 +1326,16 @@ main(int argc, char *argv[])
        sa.sa_handler = SIG_DFL;
        sigaction(SIGCHLD, &sa, NULL);
 
-       if (pflag_seen || daemonized_tracer)
+       if (nprocs != 0 || daemonized_tracer)
                startup_attach();
 
+       /* Do we want pids printed in our -o OUTFILE?
+        * -ff: no (every pid has its own file); or
+        * -f: yes (there can be more pids in the future); or
+        * -p PID1,PID2: yes (there are already more than one pid)
+        */
+       print_pid_pfx = (outfname && followfork < 2 && (followfork == 1 || nprocs > 1));
+
        if (trace() < 0)
                exit(1);
 
@@ -2094,10 +2096,12 @@ printleader(struct tcb *tcp)
 
        printing_tcp = tcp;
        curcol = 0;
-       if ((followfork == 1 || pflag_seen > 1) && outfname)
+
+       if (print_pid_pfx)
                tprintf("%-5d ", tcp->pid);
        else if (nprocs > 1 && !outfname)
                tprintf("[pid %5u] ", tcp->pid);
+
        if (tflag) {
                char str[sizeof("HH:MM:SS")];
                struct timeval tv, dtv;