Re: [Xen-devel] Errors of doing "make install-tools" with xen-4.2-unstable?

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-05-11 at 16:12 +0100, Bei Guan wrote:
> 
> 2012/5/11 Ian Campbell <Ian.Campbell@xxxxxxxxxx>
>         On Fri, 2012-05-11 at 15:08 +0100, Bei Guan wrote:
>         > When I do the "make install-tools" with xen-4.2-unstable,
>         there are
>         > some errors about "warn_unused_result".
>         > Is it the error in code or the error in the compiling
>         environment?
>         > Thank you so much.
>         
>         
>         This commit
>                changeset:   25275:27d63b9f111a
>                user:        Keir Fraser <keir@xxxxxxx>
>                date:        Thu May 10 11:22:18 2012 +0100
>                summary:     blktap2: Do not build with -O0
>         has caused more warnings to be generated by the compiler,
>         which in turn
>         leads to build failures. Since this is a compiler specific
>         thing we are
>         still tracking them all down.
>         
>         Can you confirm which versionof xen-unstable.hg you are using
>         -- there
>         have been several fixup patches since the above. If you are
>         completely
>         up to date and you still see errors we can dig into whatever
>         is left.
> 
> Thank you for your reply. I have used "hg pull; hg update" to update
> to the latest Xen and it is the version info:
> 
> root@gavin-desktop:~/Xen/xen-4.2-unstable# hg tip
> changeset:   25287:54c8c9eaee92
> tag:         tip
> user:        Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
> date:        Fri Apr 27 11:09:26 2012 +0200
> summary:     docs: add vpmu description to xen-command-line.markdown
> 
> But, it still has the same errors.

Thanks, looks like we still need to fix these errors then.

I'm not really happy with the following, but it's no worse than things
are today...

Bei, I don't see these build failures, does this work for you?

8<------------------------------------------------------

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1336751175 -3600
# Node ID 15ed8f45c4e57a1e206af020e0ff17b792108e99
# Parent  adc74e492edfee6cf44e433e3e93743a3cf71999
blktap: avoid attribute warn_unused_result build failures.

I'm not proud of this, but since none of these callers of read/write have any
other error handling and return void themselves (for several links up the call
chain AFAICT) and because I don't really want to get into a massive reworking
of blktap2 I suppose it is at least pragmatic

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

diff -r adc74e492edf -r 15ed8f45c4e5 tools/blktap2/drivers/tapdisk-log.c
--- a/tools/blktap2/drivers/tapdisk-log.c       Fri May 11 16:19:16 2012 +0100
+++ b/tools/blktap2/drivers/tapdisk-log.c       Fri May 11 16:46:15 2012 +0100
@@ -247,7 +247,7 @@ tlog_flush(void)
        wsize = ((size + 511) & (~511));
 
        memset(tapdisk_log.buf + size, '\n', wsize - size);
-       write(fd, tapdisk_log.buf, wsize);
+       (void)write(fd, tapdisk_log.buf, wsize);
 
        tapdisk_log.p = tapdisk_log.buf;
 
diff -r adc74e492edf -r 15ed8f45c4e5 tools/blktap2/drivers/tapdisk-queue.c
--- a/tools/blktap2/drivers/tapdisk-queue.c     Fri May 11 16:19:16 2012 +0100
+++ b/tools/blktap2/drivers/tapdisk-queue.c     Fri May 11 16:46:15 2012 +0100
@@ -435,7 +435,7 @@ tapdisk_lio_ack_event(struct tqueue *que
        uint64_t val;
 
        if (lio->flags & LIO_FLAG_EVENTFD)
-               read(lio->event_fd, &val, sizeof(val));
+               (void)read(lio->event_fd, &val, sizeof(val));
 }
 
 static void
diff -r adc74e492edf -r 15ed8f45c4e5 tools/blktap2/drivers/tapdisk-stream.c
--- a/tools/blktap2/drivers/tapdisk-stream.c    Fri May 11 16:19:16 2012 +0100
+++ b/tools/blktap2/drivers/tapdisk-stream.c    Fri May 11 16:46:15 2012 +0100
@@ -145,7 +145,7 @@ tapdisk_stream_poll_clear(struct tapdisk
 {
        int dummy;
 
-       read(p->pipe[POLL_READ], &dummy, sizeof(dummy));
+       (void)read(p->pipe[POLL_READ], &dummy, sizeof(dummy));
        p->set = 0;
 }
 
@@ -155,7 +155,7 @@ tapdisk_stream_poll_set(struct tapdisk_s
        int dummy = 0;
 
        if (!p->set) {
-               write(p->pipe[POLL_WRITE], &dummy, sizeof(dummy));
+               (void)write(p->pipe[POLL_WRITE], &dummy, sizeof(dummy));
                p->set = 1;
        }
 }
@@ -203,7 +203,7 @@ tapdisk_stream_print_request(struct tapd
 {
        unsigned long idx = (unsigned long)tapdisk_stream_request_idx(s, sreq);
        char *buf = (char *)MMAP_VADDR(s->vbd->ring.vstart, idx, 0);
-       write(s->out_fd, buf, sreq->secs << SECTOR_SHIFT);
+       (void)write(s->out_fd, buf, sreq->secs << SECTOR_SHIFT);
 }
 
 static void
diff -r adc74e492edf -r 15ed8f45c4e5 tools/blktap2/drivers/tapdisk2.c
--- a/tools/blktap2/drivers/tapdisk2.c  Fri May 11 16:19:16 2012 +0100
+++ b/tools/blktap2/drivers/tapdisk2.c  Fri May 11 16:46:15 2012 +0100
@@ -79,7 +79,12 @@ main(int argc, char *argv[])
        if (optind != argc)
                usage(argv[0], EINVAL);
 
-       chdir("/");
+       if (chdir("/")) {
+               DPRINTF("failed to chdir(/): %d\n", errno);
+               err = 1;
+               goto out;
+       }
+
        tapdisk_start_logging("tapdisk2");
 
        err = tapdisk_server_init();



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