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Date:   Fri, 5 Oct 2018 16:47:16 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Colin McCabe <colin@...cabe.xyz>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
        Linux Trace Devel <linux-trace-devel@...r.kernel.org>
Subject: Re: [PATCH v3] tools/lib/traceevent: Replace str_error_r() with an
 open coded implementation

Em Fri, Oct 05, 2018 at 09:27:16AM -0700, Colin McCabe escreveu:
> Hmm.  Did you consider setting the ifdefs you can set to always get the POSIX version of strerror_r?

Yes, didn't work for tools/perf, that uses _GNU_SOURCE, so we would have
the headers with that and the .c with an explicit undef _GNU_SOURCE,
that didn't fly, at least in my experiments, and that may be the case
with just some odd distros, working with others.

Having a separate .c file that first thing it does is to undef
_GNU_SOURCE, then include the necessary headers, then use strerror_r was
what worked accross the 67 environments in my containers:

   1 alpine:3.4                    : Ok   gcc (Alpine 5.3.0) 5.3.0
   2 alpine:3.5                    : Ok   gcc (Alpine 6.2.1) 6.2.1 20160822
   3 alpine:3.6                    : Ok   gcc (Alpine 6.3.0) 6.3.0
   4 alpine:3.7                    : Ok   gcc (Alpine 6.4.0) 6.4.0
   5 alpine:3.8                    : Ok   gcc (Alpine 6.4.0) 6.4.0
   6 alpine:edge                   : Ok   gcc (Alpine 6.4.0) 6.4.0
   7 amazonlinux:1                 : Ok   gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-28)
   8 amazonlinux:2                 : Ok   gcc (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5)
   9 android-ndk:r12b-arm          : Ok   arm-linux-androideabi-gcc (GCC) 4.9.x 20150123 (prerelease)
  10 android-ndk:r15c-arm          : Ok   arm-linux-androideabi-gcc (GCC) 4.9.x 20150123 (prerelease)
  11 centos:5                      : Ok   gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-55)
  12 centos:6                      : Ok   gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-23)
  13 centos:7                      : Ok   gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-28)
  14 clearlinux:latest             : Ok   gcc (Clear Linux OS for Intel Architecture) 8.2.1 20180502
  15 debian:7                      : Ok   gcc (Debian 4.7.2-5) 4.7.2
  16 debian:8                      : Ok   gcc (Debian 4.9.2-10+deb8u1) 4.9.2
  17 debian:9                      : Ok   gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516
  18 debian:experimental           : Ok   gcc (Debian 8.2.0-7) 8.2.0
  19 debian:experimental-x-arm64   : Ok   aarch64-linux-gnu-gcc (Debian 8.2.0-4) 8.2.0
  20 debian:experimental-x-mips    : Ok   mips-linux-gnu-gcc (Debian 8.1.0-12) 8.1.0
  21 debian:experimental-x-mips64  : Ok   mips64-linux-gnuabi64-gcc (Debian 8.1.0-12) 8.1.0
  22 debian:experimental-x-mipsel  : Ok   mipsel-linux-gnu-gcc (Debian 8.1.0-12) 8.1.0
  23 fedora:20                     : Ok   gcc (GCC) 4.8.3 20140911 (Red Hat 4.8.3-7)
  24 fedora:21                     : Ok   gcc (GCC) 4.9.2 20150212 (Red Hat 4.9.2-6)
  25 fedora:22                     : Ok   gcc (GCC) 5.3.1 20160406 (Red Hat 5.3.1-6)
  26 fedora:23                     : Ok   gcc (GCC) 5.3.1 20160406 (Red Hat 5.3.1-6)
  27 fedora:24                     : Ok   gcc (GCC) 6.3.1 20161221 (Red Hat 6.3.1-1)
  28 fedora:24-x-ARC-uClibc        : Ok   arc-linux-gcc (ARCompact ISA Linux uClibc toolchain 2017.09-rc2) 7.1.1 20170710
  29 fedora:25                     : Ok   gcc (GCC) 6.4.1 20170727 (Red Hat 6.4.1-1)
  30 fedora:26                     : Ok   gcc (GCC) 7.3.1 20180130 (Red Hat 7.3.1-2)
  31 fedora:27                     : Ok   gcc (GCC) 7.3.1 20180712 (Red Hat 7.3.1-6)
  32 fedora:28                     : Ok   gcc (GCC) 8.1.1 20180712 (Red Hat 8.1.1-5)
  33 fedora:rawhide                : Ok   gcc (GCC) 8.2.1 20180905 (Red Hat 8.2.1-3)
  34 gentoo-stage3-amd64:latest    : Ok   gcc (Gentoo 7.3.0-r3 p1.4) 7.3.0
  35 mageia:5                      : Ok   gcc (GCC) 4.9.2
  36 mageia:6                      : Ok   gcc (Mageia 5.5.0-1.mga6) 5.5.0
  37 opensuse:13.2                 : Ok   gcc (SUSE Linux) 4.8.3 20140627 [gcc-4_8-branch revision 212064]
  38 opensuse:42.1                 : Ok   gcc (SUSE Linux) 4.8.5
  39 opensuse:42.2                 : Ok   gcc (SUSE Linux) 4.8.5
  40 opensuse:42.3                 : Ok   gcc (SUSE Linux) 4.8.5
  41 opensuse:tumbleweed           : Ok   gcc (SUSE Linux) 7.3.1 20180323 [gcc-7-branch revision 258812]
  42 oraclelinux:6                 : Ok   gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-23.0.1)
  43 oraclelinux:7                 : Ok   gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-28.0.1)
  44 ubuntu:12.04.5                : Ok   gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
  45 ubuntu:14.04.4                : Ok   gcc (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4
  46 ubuntu:14.04.4-x-linaro-arm64 : Ok   aarch64-linux-gnu-gcc (Linaro GCC 5.5-2017.10) 5.5.0
  47 ubuntu:16.04                  : Ok   gcc (Ubuntu 5.4.0-6ubuntu1~16.04.10) 5.4.0 20160609
  48 ubuntu:16.04-x-arm            : Ok   arm-linux-gnueabihf-gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
  49 ubuntu:16.04-x-arm64          : Ok   aarch64-linux-gnu-gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
  50 ubuntu:16.04-x-powerpc        : Ok   powerpc-linux-gnu-gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
  51 ubuntu:16.04-x-powerpc64	   : Ok   powerpc64-linux-gnu-gcc (Ubuntu/IBM 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
  52 ubuntu:16.04-x-powerpc64el    : Ok   powerpc64le-linux-gnu-gcc (Ubuntu/IBM 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
  53 ubuntu:16.04-x-s390           : Ok   s390x-linux-gnu-gcc (Ubuntu 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
  54 ubuntu:16.10                  : Ok   gcc (Ubuntu 6.2.0-5ubuntu12) 6.2.0 20161005
  55 ubuntu:17.10                  : Ok   gcc (Ubuntu 7.2.0-8ubuntu3.2) 7.2.0
  56 ubuntu:18.04                  : Ok   gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
  57 ubuntu:18.04-x-arm            : Ok   arm-linux-gnueabihf-gcc (Ubuntu/Linaro 7.3.0-16ubuntu3) 7.3.0
  58 ubuntu:18.04-x-arm64          : Ok   aarch64-linux-gnu-gcc (Ubuntu/Linaro 7.3.0-16ubuntu3) 7.3.0
  59 ubuntu:18.04-x-m68k           : Ok   m68k-linux-gnu-gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
  60 ubuntu:18.04-x-powerpc        : Ok   powerpc-linux-gnu-gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
  61 ubuntu:18.04-x-powerpc64	   : Ok   powerpc64-linux-gnu-gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
  62 ubuntu:18.04-x-powerpc64el    : Ok   powerpc64le-linux-gnu-gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
  63 ubuntu:18.04-x-riscv64        : Ok   riscv64-linux-gnu-gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
  64 ubuntu:18.04-x-s390           : Ok   s390x-linux-gnu-gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
  65 ubuntu:18.04-x-sh4            : Ok   sh4-linux-gnu-gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
  66 ubuntu:18.04-x-sparc64        : Ok   sparc64-linux-gnu-gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
  67 ubuntu:18.10                  : Ok   gcc (Ubuntu 8.2.0-4ubuntu1) 8.2.0
 
> best,
> Colin
> 
> 
> On Fri, Oct 5, 2018, at 08:30, Steven Rostedt wrote:
> > On Tue, 2 Oct 2018 17:55:39 -0400
> > Steven Rostedt <rostedt@...dmis.org> wrote:
> > 
> > > From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> > > 
> > > While working on having PowerTop use libtracevent as a shared object
> > > library, Tzvetomir hit "str_error_r not defined". This was added by commit
> > > c3cec9e68f12d ("tools lib traceevent: Use str_error_r()") because
> > > strerror_r() has two definitions, where one is GNU specific, and the other
> > > is XSI complient. The strerror_r() is in a wrapper str_error_r() to keep the
> > > code from having to worry about which compiler is being used.
> > > 
> > > The problem is that str_error_r() is external to libtraceevent, and not part
> > > of the library. If it is used as a shared object then the tools using it
> > > will need to define that function. I do not want that function defined in
> > > libtraceevent itself, as it is out of scope for that library.
> > > 
> > > As there's only a single instance of this call, I replaced it with an open
> > > coded algorithm that uses sys_nerr and sys_errlist error array with
> > > strncpy() to place the error message in the given buffer. We don't need to
> > > worry about the errors that strerror_r() returns. If the buffer isn't big
> > > enough, we simply truncate it.
> > > 
> > > The sys_nerr and sys_errlist idea was found here:
> > > 
> > >   http://www.club.cc.cmu.edu/~cmccabe/blog_strerror.html
> > > 
> > > Cc: Colin Patrick McCabe <cmccabe@...mni.cmu.edu>
> > > Reported-by: Tzvetomir Stoyanov <tstoyanov@...are.com>
> > > Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> > > ---
> > > Changes since v2:
> > > 
> > >   Use sys_nerr and sys_errlist idea.
> > > 
> > >  tools/lib/traceevent/event-parse.c | 9 +++++++--
> > >  1 file changed, 7 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> > > index 7980fc6c3bac..d23d10bc5314 100644
> > > --- a/tools/lib/traceevent/event-parse.c
> > > +++ b/tools/lib/traceevent/event-parse.c
> > > @@ -18,7 +18,6 @@
> > >  #include <errno.h>
> > >  #include <stdint.h>
> > >  #include <limits.h>
> > > -#include <linux/string.h>
> > >  #include <linux/time64.h>
> > >  
> > >  #include <netinet/in.h>
> > > @@ -6215,7 +6214,13 @@ int tep_strerror(struct tep_handle *pevent __maybe_unused,
> > >  	const char *msg;
> > >  
> > >  	if (errnum >= 0) {
> > > -		str_error_r(errnum, buf, buflen);
> > > +		if (buflen > 0) {
> > > +			if (errnum < sys_nerr)
> > > +				strncpy(buf, sys_errlist[errnum], buflen);
> > > +			else
> > > +				snprintf(buf, buflen, "Unknown error %d", errnum);
> > > +			buf[buflen - 1] = 0;
> > > +		}
> > 
> > Bah, I now get warnings that sys_nerr and sys_errlist are deprecated.
> > 
> > OK, so going back to just using the racy strerror() should be good
> > enough, as this incompatibility with strerror_r() is a disaster!
> > 
> > -- Steve
> > 
> > 
> > >  		return 0;
> > >  	}
> > >  
> > 
> 
> 
> C.

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