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Bug/Undocumented behaviour

From: Philipp Marek <philipp_at_marek.priv.at>
Date: 2007-10-18 19:52:48 CEST

Hello everybody,

Ben suggested on IRC that I ask here.

While debugging FSVS (fsvs.tigris.org) via IRC a user gave me a stack dump,
it that we can see that the svn stream functions get called with
parameters in an undocumented range, ie.
svn_stream_write()/svn_stream_read() with data=NULL - and that for an
unlimited number of times at the end of a file.

In FSVS I resolved that by assuming that data=NULL means more or less the same
as a svn_stream_close(), which fixed the apparent problem.

I'm not sure whether that is a bug in libsvn_ra or below, or whether that is
normal behaviour ... it happens only for http:// and https://, not for file://
or svn+ssh://.

Here's the stackdump ... indented and marked:

  #0 0x001e57a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
  #1 0x002b8c93 in __read_nocancel () from /lib/tls/libc.so.6
  #2 0x0805237b in sigDebug (num=11) at fsvs.c:647
  #3 <signal handler called>
  #4 0x0804bfa8 in cs___update_manber (mb_f=0x8071960, data=0x0, len=0) at checksum.c:660
1-#5 0x0804c1aa in cs___mnbs_write (baton=0x8071960, data=0x0, len=0xbfe72efc) at checksum.c:738
--#6 0x00cea44e in svn_stream_write (stream=0x9cfc348, data=0x0, len=0x0) at subversion/libsvn_subr/stream.c:107
2-#7 0x00c07a41 in get_file_reader (userdata=0xbfe73024, buf=0x0, len=0) at subversion/libsvn_ra_dav/fetch.c:709
  #8 0x00c84f40 in ne_redirect_location () from /usr/lib/libneon.so.24
  #9 0x00c7b420 in ne_read_response_block () from /usr/lib/libneon.so.24
  #10 0x00c7c79b in ne_request_dispatch () from /usr/lib/libneon.so.24
  #11 0x00c1486b in svn_ra_dav__request_dispatch (code_p=0x0, request=0x9ccf6b0, session=0x0, method=0x3287bc "", url=0x3287bc "", okay_1=200, okay_2=226, pool=0x9cfc280) at subversion/libsvn_ra_dav/util.c:978
  #12 0x00c075c0 in custom_get_request (sess=0x9c5c360, url=0x9cfe620 "/fsvs-master/!svn/bc/6/hosts/cobtest/etc/cobbler/centos4-server.ks",relpath=0x9cebd8e "centos4-server.ks", reader=0xc079cb <get_file_reader>, subctx=0xbfe730c4, get_wc_prop=0, cb_baton=0x0, use_base=0, pool=0x9cfc280) at subversion/libsvn_ra_dav/fetch.c:490
  #13 0x00c07d96 in svn_ra_dav__get_file (session=0x9c50480, path=0x9cebd8e "centos4-server.ks", revision=6, stream=0x9cfc348, fetched_rev=0xbfe731dc, props=0xbfe731a8, pool=0x9cfc280) at subversion/libsvn_ra_dav/fetch.c:892
3-#14 0x00adcbc4 in svn_ra_get_file (session=0x3287bc, path=0x0, revision=0, stream=0x0, fetched_rev=0x0, props=0x0, pool=0x0) at subversion/libsvn_ra/ra_loader.c:429
  #15 0x08059cca in rev__get_file (sts=0x9cdcc60, revision=6, fetched=0xbfe731dc, only_tmp=0x0, pool=0x9cdac70) at revert.c:273
  #16 0x0805a6fd in rev__do_changed (session=0x9c50480, dir=0xbfe7329c, pool=0x9c45240) at revert.c:678
  #17 0x0805dcbc in up__work (root=0xbfe7329c, argc=0, argv=0xbfe733cc) at update.c:1363
  #18 0x08052cd0 in main (argc=0, args=0xbfe733c4) at fsvs.c:991
  #19 0x00213de3 in __libc_start_main () from /lib/tls/libc.so.6
  #20 0x0804ac55 in _start ()

In (3) the call into the subversion libraries can be seen ...
svn_ra_get_file() on a https:// URL. In (1) FSVS gets its svn_stream
handler called ... with NULLs propagating from at least (2).

The documentation at
http://svn.collab.net/svn-doxygen/group__svn__io__byte__streams.html#ga0
doesn't mention NULL parameters.

Sadly only the FSVS binary was compiled with debug information (the svn
libraries were off-the-shelf from CentOS5).

Any ideas? Thank you in advance.

Regards,

Phil

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Received on Thu Oct 18 19:53:03 2007

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