richardphibel / rpms / systemd

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From 538bd9b42dabf1145cf7ab77f32347d516b01e88 Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Tue, 12 May 2020 18:56:34 +0200
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Subject: [PATCH] journald: rework pid change handling
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Let's introduce an explicit line ending marker for line endings due to
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pid change.
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Let's also make sure we don't get confused with buffer management.
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Fixes: #15654
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(cherry picked from commit 45ba1ea5e9264d385fa565328fe957ef1d78caa1)
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Resolves: #2029426
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---
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 src/journal/journald-stream.c | 99 +++++++++++++++++++++++------------
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 1 file changed, 66 insertions(+), 33 deletions(-)
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diff --git a/src/journal/journald-stream.c b/src/journal/journald-stream.c
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index ab1a855943..5be5b0939c 100644
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--- a/src/journal/journald-stream.c
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+++ b/src/journal/journald-stream.c
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@@ -54,6 +54,7 @@ typedef enum LineBreak {
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         LINE_BREAK_NUL,
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         LINE_BREAK_LINE_MAX,
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         LINE_BREAK_EOF,
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+        LINE_BREAK_PID_CHANGE,
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         _LINE_BREAK_MAX,
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         _LINE_BREAK_INVALID = -1,
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 } LineBreak;
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@@ -310,6 +311,7 @@ static int stdout_stream_log(
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                 [LINE_BREAK_NUL]        = "_LINE_BREAK=nul",
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                 [LINE_BREAK_LINE_MAX]   = "_LINE_BREAK=line-max",
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                 [LINE_BREAK_EOF]        = "_LINE_BREAK=eof",
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+                [LINE_BREAK_PID_CHANGE] = "_LINE_BREAK=pid-change",
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         };
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         const char *c = line_break_field_table[line_break];
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@@ -431,21 +433,43 @@ static int stdout_stream_line(StdoutStream *s, char *p, LineBreak line_break) {
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         assert_not_reached("Unknown stream state");
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 }
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-static int stdout_stream_scan(StdoutStream *s, bool force_flush) {
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-        char *p;
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-        size_t remaining;
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+static int stdout_stream_found(
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+                StdoutStream *s,
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+                char *p,
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+                size_t l,
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+                LineBreak line_break) {
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+
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+        char saved;
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         int r;
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         assert(s);
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+        assert(p);
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+
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+        /* Let's NUL terminate the specified buffer for this call, and revert back afterwards */
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+        saved = p[l];
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+        p[l] = 0;
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+        r = stdout_stream_line(s, p, line_break);
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+        p[l] = saved;
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-        p = s->buffer;
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-        remaining = s->length;
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+        return r;
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+}
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+
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+static int stdout_stream_scan(
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+                StdoutStream *s,
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+                char *p,
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+                size_t remaining,
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+                LineBreak force_flush,
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+                size_t *ret_consumed) {
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-        /* XXX: This function does nothing if (s->length == 0) */
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+        size_t consumed = 0;
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+        int r;
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+
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+        assert(s);
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+        assert(p);
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         for (;;) {
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                 LineBreak line_break;
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-                size_t skip;
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+                size_t skip, found;
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                 char *end1, *end2;
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                 end1 = memchr(p, '\n', remaining);
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@@ -453,43 +477,40 @@ static int stdout_stream_scan(StdoutStream *s, bool force_flush) {
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                 if (end2) {
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                         /* We found a NUL terminator */
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-                        skip = end2 - p + 1;
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+                        found = end2 - p;
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+                        skip = found + 1;
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                         line_break = LINE_BREAK_NUL;
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                 } else if (end1) {
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                         /* We found a \n terminator */
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-                        *end1 = 0;
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-                        skip = end1 - p + 1;
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+                        found = end1 - p;
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+                        skip = found + 1;
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                         line_break = LINE_BREAK_NEWLINE;
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                 } else if (remaining >= s->server->line_max) {
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                         /* Force a line break after the maximum line length */
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-                        *(p + s->server->line_max) = 0;
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-                        skip = remaining;
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+                        found = skip = s->server->line_max;
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                         line_break = LINE_BREAK_LINE_MAX;
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                 } else
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                         break;
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-                r = stdout_stream_line(s, p, line_break);
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+                r = stdout_stream_found(s, p, found, line_break);
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                 if (r < 0)
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                         return r;
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-                remaining -= skip;
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                 p += skip;
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+                consumed += skip;
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+                remaining -= skip;
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         }
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-        if (force_flush && remaining > 0) {
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-                p[remaining] = 0;
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-                r = stdout_stream_line(s, p, LINE_BREAK_EOF);
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+        if (force_flush >= 0 && remaining > 0) {
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+                r = stdout_stream_found(s, p, remaining, force_flush);
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                 if (r < 0)
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                         return r;
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-                p += remaining;
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-                remaining = 0;
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+                consumed += remaining;
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         }
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-        if (p > s->buffer) {
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-                memmove(s->buffer, p, remaining);
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-                s->length = remaining;
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-        }
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+        if (ret_consumed)
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+                *ret_consumed = consumed;
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         return 0;
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 }
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@@ -497,11 +518,12 @@ static int stdout_stream_scan(StdoutStream *s, bool force_flush) {
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 static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
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         uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
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         StdoutStream *s = userdata;
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+        size_t limit, consumed;
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         struct ucred *ucred = NULL;
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         struct cmsghdr *cmsg;
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         struct iovec iovec;
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-        size_t limit;
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         ssize_t l;
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+        char *p;
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         int r;
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         struct msghdr msghdr = {
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@@ -529,7 +551,7 @@ static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents,
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         /* Try to make use of the allocated buffer in full, but never read more than the configured line size. Also,
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          * always leave room for a terminating NUL we might need to add. */
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         limit = MIN(s->allocated - 1, s->server->line_max);
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-
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+        assert(s->length <= limit);
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         iovec = IOVEC_MAKE(s->buffer + s->length, limit - s->length);
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         l = recvmsg(s->fd, &msghdr, MSG_DONTWAIT|MSG_CMSG_CLOEXEC);
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@@ -543,7 +565,7 @@ static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents,
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         cmsg_close_all(&msghdr);
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         if (l == 0) {
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-                stdout_stream_scan(s, true);
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+                (void) stdout_stream_scan(s, s->buffer, s->length, /* force_flush = */ LINE_BREAK_EOF, NULL);
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                 goto terminate;
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         }
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@@ -562,22 +584,33 @@ static int stdout_stream_process(sd_event_source *es, int fd, uint32_t revents,
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          * in the meantime.
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          */
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         if (ucred && ucred->pid != s->ucred.pid) {
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-                /* force out any previously half-written lines from a
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-                 * different process, before we switch to the new ucred
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-                 * structure for everything we just added */
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-                r = stdout_stream_scan(s, true);
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+                /* Force out any previously half-written lines from a different process, before we switch to
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+                 * the new ucred structure for everything we just added */
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+                r = stdout_stream_scan(s, s->buffer, s->length, /* force_flush = */ LINE_BREAK_PID_CHANGE, NULL);
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                 if (r < 0)
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                         goto terminate;
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-                s->ucred = *ucred;
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                 s->context = client_context_release(s->server, s->context);
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+
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+                p = s->buffer + s->length;
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+        } else {
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+                p = s->buffer;
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+                l += s->length;
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         }
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-        s->length += l;
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-        r = stdout_stream_scan(s, false);
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+        /* Always copy in the new credentials */
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+        if (ucred)
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+                s->ucred = *ucred;
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+
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+        r = stdout_stream_scan(s, p, l, _LINE_BREAK_INVALID, &consumed);
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         if (r < 0)
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                 goto terminate;
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+        /* Move what wasn't consumed to the front of the buffer */
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+        assert(consumed <= (size_t) l);
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+        s->length = l - consumed;
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+        memmove(s->buffer, p + consumed, s->length);
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+
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         return 1;
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 terminate: