http://sourceware.org/ml/gdb-patches/2014-08/msg00376.html

Subject: Re: --with-babeltrace generates many FAILs

On 08/19/2014 10:07 PM, Jan Kratochvil wrote:

>  * '#if HAVE_LIBBABELTRACE1_1_0' could have a comment that >=1.1.1 rejects the

>    faked packet (what you described in the mail but not in the patch).

Fixed.  To be precise, >= 1.1.2 rejects the faked packet, 1.1.1

doesn't.  See the table I posted.

>  * It is always better to check for feature/defect than to check for version.

>    For example because various distros backport various fixes (unfortunately

>    including their possible regressions/defects) and so version checks may be

>    misleading then.  At least in this case it seems to me as possible to check

>    how libbacktrace behaves from configure; although maybe it is not easy

>    enough, not sure.

In order to check libbabeltrace's behaviour in configure, we have to write

a c program to generate CTF data and read the trace data via

babeltrace or any program (using libbabeltrace) written by ourselves.

It is not easy to do so.

The patch is updated.  OK to apply?

-- 

Yao (齐尧)

Subject: [PATCH] Check babeltrace 1.1.0

Subject: [PATCH] Check babeltrace 1.1.0

When GDB uses recent version of babeltrace, such as 1.2.x, we'll see

such error emitted from babeltrace library,

 (gdb) target ctf .../gdb/testsuite/gdb.trace/actions.ctf

 [error] Invalid CTF stream: content size is smaller than

packet headers.

 [error] Stream index creation error.

 [error] Open file stream error.

The problem can be reproduce out of GDB too, using babeltrace,

 $ babeltrace ./fake-packet.ctf/

 [error] Invalid CTF stream: content size is smaller than packet headers.

 [error] Stream index creation error.

 [error] Open file stream error.

Recent babeltrace library becomes more strict on CTF, and complains

about one "faked packet" GDB adds, when saving trace data in ctf

format from GDB.  babeltrace 1.1.0 has a bug that it can't read trace

data smaller than a certain size (see https://bugs.lttng.org/issues/450).

We workaround it in GDB to append some meaningless data in a faked

packet to make sure trace file is large enough (see ctf.c:ctf_end).

The babeltrace issue was fixed in 1.1.1 release.  However, babeltrace

recent release (since 1.1.2) starts to complain about such faked

packet.  Here is a table shows that whether faked packet or no faked

packet is supported by various babeltrace releases,

        faked packet      no faked packet

1.1.0      Yes                 No

1.1.1      Yes                 Yes

1.1.2      No                  Yes

1.2.0      No                  Yes

We decide to include the code to workaround 1.1.0 issue only if 1.1.0

is used.  We choose pkg-config to check babeltrace's version in

configure.

gdb:

2014-08-20  Yao Qi  <yao@codesourcery.com>

	* configure.ac: Disable babeltrace support if pkg-config is

	missing.  Use pkg-config to check whether libbabeltrace is

	1.1.0.

	* config.in: Regenerate.

	* configure: Regenerate.

	* ctf.c (CTF_FILE_MIN_SIZE): Remove.

	(ctf_end): Wrap the code with

	#if HAVE_LIBBABELTRACE1_1_0 #endif.

	[HAVE_LIBBABELTRACE1_1_0] (CTF_FILE_MIN_SIZE): New macro.

---

 gdb/config.in    |  3 +++

 gdb/configure    | 25 +++++++++++++++++++++++++

 gdb/configure.ac | 22 ++++++++++++++++++++++

 gdb/ctf.c        | 25 ++++++++++++++++---------

 4 files changed, 66 insertions(+), 9 deletions(-)

diff --git a/gdb/config.in b/gdb/config.in

index b853412..54152cd 100644

--- a/gdb/config.in

+++ b/gdb/config.in

@@ -183,6 +183,9 @@

 /* Define if you have the babeltrace library. */

 #undef HAVE_LIBBABELTRACE

+/* Define to 1 if you have libbabeltrace 1.1.0 */

+#undef HAVE_LIBBABELTRACE1_1_0

+

 /* Define to 1 if you have the `dl' library (-ldl). */

 #undef HAVE_LIBDL

diff --git a/gdb/configure b/gdb/configure

index 9253e28..d4e2c6e 100755

--- a/gdb/configure

+++ b/gdb/configure

@@ -14817,6 +14817,11 @@ $as_echo "$with_babeltrace" >&6; }

 if test "x$with_babeltrace" = "xno"; then

   { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: babletrace support disabled; GDB is unable to read CTF data." >&5

 $as_echo "$as_me: WARNING: babletrace support disabled; GDB is unable to read CTF data." >&2;}

+elif test "${pkg_config_prog_path}" = "missing"; then

+  # pkg-config is used to check the version of libbabeltrace.  If pkg-config

+  # is missing, we have to disable babeltrace support.

+  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: pkg-config not found, babletrace support disabled" >&5

+$as_echo "$as_me: WARNING: pkg-config not found, babletrace support disabled" >&2;}

 else

   # Append -Werror to CFLAGS so that configure can catch the warning

   # "assignment from incompatible pointer type", which is related to

@@ -15307,6 +15312,26 @@ $as_echo "$LIBBABELTRACE" >&6; }

        { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: babeltrace is missing or unusable; GDB is unable to read CTF data." >&5

 $as_echo "$as_me: WARNING: babeltrace is missing or unusable; GDB is unable to read CTF data." >&2;}

      fi

+  else

+     # Need to know whether libbabeltrace is 1.1.0.

+     pkg_config_path=

+     for x in $LTLIBBABELTRACE; do

+       case "$x" in

+         -L*)

+	   dir=`echo "X$x" | sed -e 's/^X-L//'`

+	   if test -d "$dir/pkgconfig"; then

+	     pkg_config_path="${pkg_config_path}${pkg_config_path:+:}$dir/pkgconfig"

+	   fi

+	   ;;

+       esac

+     done

+

+     `PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$pkg_config_path ${pkg_config_prog_path} babeltrace = 1.1.0`

+     if test "$?" -eq 0 ; then

+

+$as_echo "#define HAVE_LIBBABELTRACE1_1_0 1" >>confdefs.h

+

+     fi

   fi

 fi

diff --git a/gdb/configure.ac b/gdb/configure.ac

index 61919b4..1d8d400 100644

--- a/gdb/configure.ac

+++ b/gdb/configure.ac

@@ -2420,6 +2420,10 @@ AC_MSG_RESULT([$with_babeltrace])

 if test "x$with_babeltrace" = "xno"; then

   AC_MSG_WARN([babletrace support disabled; GDB is unable to read CTF data.])

+elif test "${pkg_config_prog_path}" = "missing"; then

+  # pkg-config is used to check the version of libbabeltrace.  If pkg-config

+  # is missing, we have to disable babeltrace support.

+  AC_MSG_WARN([pkg-config not found, babletrace support disabled])

 else

   # Append -Werror to CFLAGS so that configure can catch the warning

   # "assignment from incompatible pointer type", which is related to

@@ -2450,6 +2454,24 @@ else

      else

        AC_MSG_WARN([babeltrace is missing or unusable; GDB is unable to read CTF data.])

      fi

+  else

+     # Need to know whether libbabeltrace is 1.1.0.

+     pkg_config_path=

+     for x in $LTLIBBABELTRACE; do

+       case "$x" in

+         -L*)

+	   dir=`echo "X$x" | sed -e 's/^X-L//'`

+	   if test -d "$dir/pkgconfig"; then

+	     pkg_config_path="${pkg_config_path}${pkg_config_path:+:}$dir/pkgconfig"

+	   fi

+	   ;;

+       esac

+     done

+

+     `PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$pkg_config_path ${pkg_config_prog_path} babeltrace = 1.1.0`

+     if test "$?" -eq 0 ; then

+       AC_DEFINE([HAVE_LIBBABELTRACE1_1_0], [1], [Define to 1 if you have libbabeltrace 1.1.0])

+     fi

   fi

 fi

diff --git a/gdb/ctf.c b/gdb/ctf.c

index df645c0..684da50 100644

--- a/gdb/ctf.c

+++ b/gdb/ctf.c

@@ -623,11 +623,6 @@ ctf_write_definition_end (struct trace_file_writer *self)

   self->ops->frame_ops->end (self);

 }

-/* The minimal file size of data stream.  It is required by

-   babeltrace.  */

-

-#define CTF_FILE_MIN_SIZE		4096

-

 /* This is the implementation of trace_file_write_ops method

    end.  */

@@ -637,10 +632,21 @@ ctf_end (struct trace_file_writer *self)

   struct ctf_trace_file_writer *writer = (struct ctf_trace_file_writer *) self;

   gdb_assert (writer->tcs.content_size == 0);

-  /* The babeltrace requires or assumes that the size of datastream

-     file is greater than 4096 bytes.  If we don't generate enough

-     packets and events, create a fake packet which has zero event,

-      to use up the space.  */

+

+#if HAVE_LIBBABELTRACE1_1_0

+  /* The babeltrace-1.1.0 requires or assumes that the size of datastream

+     file is greater than 4096 bytes.  This was fixed after 1.1.0 release.

+     See https://bugs.lttng.org/issues/450

+     If we don't generate enough packets and events, create a fake packet

+     which has zero event, to use up the space.  However, babeltrace

+     release (since 1.1.2) starts to complain about such faked packet,

+     we include this workaround only for babeltrace 1.1.0.  */

+

+  /* The minimal file size of data stream.  It is required by

+     babeltrace.  */

+

+#define CTF_FILE_MIN_SIZE		4096

+

   if (writer->tcs.packet_start < CTF_FILE_MIN_SIZE)

     {

       uint32_t u32;

@@ -681,6 +687,7 @@ ctf_end (struct trace_file_writer *self)

 	  ctf_save_write (&writer->tcs, &b, 1);

 	}

     }

+#endif /* HAVE_LIBBABELTRACE1_1_0 */

 }

 /* This is the implementation of trace_frame_write_ops method

-- 

1.9.3