Re: [dpdk-dev] Build is broken in dpdk-next-net

[Maxime Coquelin]

Thanks Xiangxia,

I can post it, do you agree if I add below comments?
On 03/30/2018 04:47 PM, Tonghao Zhang wrote:
I rebuild it on ubuntu 17.10 and cash it. I use the 'RTE_SET_USED' to fix it.


diff --git a/lib/librte_vhost/fd_man.c b/lib/librte_vhost/fd_man.c
index 771675718..f11803191 100644
--- a/lib/librte_vhost/fd_man.c
+++ b/lib/librte_vhost/fd_man.c
@@ -279,7 +279,8 @@ fdset_pipe_read_cb(int readfd, void *dat __rte_unused,
                    int *remove __rte_unused)
  {
         char charbuf[16];
-       read(readfd, charbuf, sizeof(charbuf));
+       int r = read(readfd, charbuf, sizeof(charbuf));
/* Just an optimization, we don't care if read() failed so ignore 
explicitly its return value to make the compiler happy */
+       RTE_SET_USED(r);
  }

  void
@@ -319,5 +320,6 @@ fdset_pipe_init(struct fdset *fdset)
  void
  fdset_pipe_notify(struct fdset *fdset)
  {
-       write(fdset->u.writefd, "1", 1);
/* Just an optimization, we don't care if write() failed so ignore 
explicitly its return value to make the compiler happy */
+       int r = write(fdset->u.writefd, "1", 1);
+       RTE_SET_USED(r);
  }

On Fri, Mar 30, 2018 at 10:28 PM, Timothy Redaelli <tredae...@redhat.com> wrote:
On Fri, 30 Mar 2018 15:27:55 +0200
Maxime Coquelin <maxime.coque...@redhat.com> wrote:

Hi Andrew,

On 03/30/2018 03:18 PM, Andrew Rybchenko wrote:
Hi all,

Build is broken in dpdk-next-net for me on Ubuntu 16.04.4:

lib/librte_vhost/fd_man.c: In function ‘fdset_pipe_read_cb’:
lib/librte_vhost/fd_man.c:284:2: error: ignoring return value of
‘read’, declared with attribute warn_unused_result
[-Werror=unused-result] read(readfd, charbuf, sizeof(charbuf)); ^
lib/librte_vhost/fd_man.c: In function ‘fdset_pipe_notify’:
lib/librte_vhost/fd_man.c:324:2: error: ignoring return value of
‘write’, declared with attribute warn_unused_result
[-Werror=unused-result] write(fdset->u.writefd, "1", 1); ^

$ gcc --version
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609

Thanks for reporting, I don't catch it with my Fedora build system:
$ gcc --version
gcc (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5)

Those kind of warnings are enabled by "-D_FORTIFY_SOURCE=2" (enabled by
default in Ubuntu [1]).

To have the same behavior on Fedora you need to set -D_FORTIFY_SOURCE=2
by hand, for example with:

# make EXTRA_CFLAGS="-D_FORTIFY_SOURCE=2"

Usually I build dpdk with the flags we also use when we build the
Fedora/RHEL package. To do that I have in my .bashrc (all in one line):

export EXTRA_CFLAGS="-O2 -g -pipe -Werror=format-security
-Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong
--param=ssp-buffer-size=4 -grecord-gcc-switches
-specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -m64 -mtune=generic
-fasynchronous-unwind-tables -Wformat"


As I understand it is broken in
ad94ade905454401b705be9e06b19e54a1c78148 vhost: add pipe event for
optimizing negotiating

I confirm it is this patch.

Xiangxia, can you provide a fix please?

Ferruh, how do you want to proceed?
Would you revert it?

Thanks,
Maxime
Andrew.


[1]
https://wiki.ubuntu.com/ToolChain/CompilerFlags#A-D_FORTIFY_SOURCE.3D2