Start debugging
You need a linked build - please have a look at the HackingIt pages, and install either using the make dev-install, or bin/ooinstall -l. Then you can start your debugging session like:
# change directory to the installation provided by make dev-install cd build/install/program source ooenv # start the debugger gdb --tui ./soffice.bin (gdb) run -writer
You soon realize that you have no debugging symbols in your build. Let's say, you need symbols for the module vcl - then you need to completely rebuild vcl using build debug=true, instead of build, like:
cd build/ooo320-m12/vcl # remove the old build rm -r unxlngi6.pro # setup the build environment source ../LinuxX86Env.Set.sh # and build build debug=true
We have the linked build, right? So now just start gdb --tui ./soffice.bin again, and this time, you have the symbols for the rebuilt module.
gdb Tips & Tricks for OOo
These instructions are mostly Linux (gdb) related, for Windows, you might consult this page. gdb is a powerful tool, but it pays off to get familiar with it a bit.
Recommended .gdbinit file
You can define macros that help you eg. examine OOo strings in your ~/.gdbinit file, so that they are always available. We recommend at least the following contents:
set history filename ~/.gdbhistory
set history save on
handle SIGPWR nostop noprint
handle SIGXCPU nostop noprint
handle SIG33 nostop noprint
tabset 4
# define "pu" command to display sal_Unicode *
define pu
set $uni = $arg0
set $len = $arg1
set $i = 0
printf "\""
while (*$uni && $i++<$len && $i<255)
if (*$uni < 0x80)
printf "%c", *(char*)$uni++
else
printf "\\x%x", *(short*)$uni++
end
end
printf "\"\n"
end
# define "pus" command to display rtl_uString
define pus
if ($arg0.buffer)
pu $arg0.buffer $arg0.length
else
print "Invalid/non-initialized rtl_uString."
end
end
# define "pou" command to display rtl::OUString
define pou
if ($arg0.pData)
pus $arg0.pData
else
print "Invalid/non-initialized OUString."
end
end
# define "ptu" command to display tools (Uni)String
define ptu
if ($arg0.mpData)
pu $arg0.mpData->maStr $arg0.mpData->mnLen
else
print "Invalid/non-initialized tools String."
end
end
# define "ps" command that will autodetect the type of the string,
# and call a function accordingly
define ps
if ($arg0.pData)
pou $arg0
else
if ($arg0.mpData)
ptu $arg0
else
if ($arg0.buffer)
pus $arg0
else
set $len = $arg1
if ($len)
pu $arg0 $len
else
# first 20 (unicode) chars
pu $arg0 20
end
end
end
end
end
document ps
ps somestring [len]
Print the content of pretty much any OpenOffice.org string.
The length parameter is only used for sal_Unicode* strings: if not
provided, the first 20 characters will be printed for those kinds
of strings.
end
If you want to define your own macros, please remember that gdb only has global variables, so be careful to choose different names.
Text user interface
One of the less known gdb features is its text user interface. Instead of plain gdb, use gdb --tui every time you want to debug. You will be able to see the context of what are you debugging all the time. Useful commands:
- Ctrl-l - refresh screen (when something prints there, etc.)
- Ctrl-x s - single key mode. In this mode
nmeansnext,sstep,rrun, and few more. To get the 'normal' gdb input line, pressspace, and start typing, likeprint whatever_variable.qexits the single key mode
Intercepting exceptions
When you want your code to stop whenever an exception is raised, do:
(gdb) catch throw
Alternatively, you can do break __cxa_throw. More info in Kohei's blog.
Examining strings
As we have already seen in HackingIt, OOo has its own set of string classes, none of which gdb understands. The recommended .gdbinit allows you to examine them using the ps macro. Let's say, you have rtl::OUString aString;, and you want to know its value in gdb:
(gdb) ps aString "the value"
Simple as that. But there are other possibilities if the above fails from some reason, like:
(gdb) print dbg_dump(aString)
This works on all UniString/ByteString/rtl::OUString/rtl::OString regardless of the type when debugging C++ code. See Caolan's write-up for details.
In case the functions dbg_dump() are not available in gdb due to linking, just copy them in your current source file from '/sal/rtl/sourc/debug_print' and add the associated includes #include <rtl/strbuf.hxx> #include <rtl/ustring.hxx>. gdb should recognize them then.
It crashes, but only in gdb
What fun - you symlinked desktop/unxlngi4.pro/bin/soffice to soffice.bin in your install tree didn't you. That works fine if you just run it, but it seems gdb unpacks the symlink and passes a fully qualified path as argv[0], which defeats the hunting for the binary in the path, so it assigns the program base path as /opt/OpenOffice/OOO_STABLE_1/desktop/unxlngi4.pro/bin and starts looking for (eg. applicat.rdb) in there. Of course when it fails to find any setup information, it silently crashes somewhere else yards away from the original problem.
It crashes, but doesn't crash
For various reasons signal handlers are trapped and life can get rather confusing; thus it's best for builders to apply something like this:
--- sal/osl/unx/signal.c
+++ sal/osl/unx/signal.c
@@ -188,6 +188,8 @@ static sal_Bool InitSignal()
bSetILLHandler = sal_True;
}
+ bSetSEGVHandler = bSetWINCHHandler = bSetILLHandler = bDoHardKill = sal_False;
+
SignalListMutex = osl_createMutex();
act.sa_handler = SignalHandlerFunction;
I can't find the code from the trace
Some methods, are described as having a special linkage, such that they can be used in callbacks; these typically have a prefix: LinkStub, so search for the latter part of the identifier in a freetext search. eg. the following builds the '?LinkStubImplHandlePaintHdl' method:
IMPL_LINK( Window, ImplHandlePaintHdl, void*, EMPTYARG )
It always crashes in sal_XErrorHdl
You are a victim of asynchronous X error reporting. Before you start gdb, do:
export SAL_SYNCHRONIZE=1
It will make all the X traffic synchronous, and report the error by the method that caused it, it'll also make OOo far slower, and the timing different.
The trace shows a crash in 'poll'
OO.o is a fairly threaded program, you're probably just looking at the wrong thread: there are not likely to be bugs in poll. Use
(gdb) thread apply all backtrace
to get a backtrace of all threads - this will most likely fail. When it does do: thread 1 then bt - most crashers occur in the 'main' thread.
What does this trace mean ?
There are several typical stack-traces that come up again and again, one would be:
#15 0x4164a501 in raise () from /lib/tls/libc.so.6 #16 0x4164bcd9 in abort () from /lib/tls/libc.so.6 #17 0x415fb5a5 in std::set_unexpected () from /home/mnagashree/m72install/program/libstdc++.so.5 #18 0x415fb5e2 in std::terminate () from /home/mnagashree/m72install/program/libstdc++.so.5 #19 0x415fb69c in __cxa_rethrow ()
This section of trace means (essentially) that an exception was thrown - but there was no-one trying to catch it. Often this means there was a missing 'try {} catch()' clause in one of the calling frames.
A great way to debug exceptions is to add a breakpoint in catch/throw, do this with catch throw or catch catch in gdb - see Intercepting Exceptions above.
Useful places to put breakpoints
If you have compiled with debugging enabled: build debug=true it is possible that you get some nice churning debug / assertion failure - and you want to get a pleasant & detailed stack-trace: to do that do break osl_assertFailedLine.
How to re-build just the relevant pieces
Often when you run gdb on a build without debugging symbols, you get an unhelpful gdb trace, but yet you can't afford the time/space to recompile all of OO.o with debugging symbols. Thus we have created a small perl helper, which will hunt for and touch files containing the symbols from your trace. This sub-set can then be re-built with debugging enabled for a better trace next time around:
gdb ./soffice.bin
...
bt
#0 0x40b4e0a1 in kill () from /lib/libc.so.6
#1 0x409acfe6 in raise () from /lib/libpthread.so.0
#2 0x447bcdbd in SfxMedium::DownLoad(Link const&) () from ./libsfx641li.so
#3 0x447be151 in SfxMedium::SfxMedium(String const&, unsigned short, unsigned char, SfxFilter const*, SfxItemSet*) ()
from ./libsfx641li.so
#4 0x448339d3 in getCppuType(com::sun::star::uno::Reference<com::sun::star::document::XImporter> const*) () from ./libsfx641li.so
...
quit
cd base/OOO_STABLE_1/sfx2
ootouch SfxMedium
build debug=true
Thus, all files referencing or implementing anything with ?SfxMedium will be touched, and hence rebuilt with debugging symbols. ootouch is available in bin/oootouch.
If you want to recompile the code in just your current directory, you can use the killobj dmake target to remove the object files:
dmake killobj dmake
Getting the build order right
The build dependencies of the modules are clearly crucial to getting a clean build. When you type 'build' in a module, first build examines prj/build.list, eg. neon/prj/build.lst:
xh neon : soltools external expat NULL
This specifies that 'soltools', 'external' and 'expat' have to be satisfactorily built and delivered before neon can be built. Occasionally these rules get broken, and people don't notice for a while.
What is a debug console ?
So OO.o contains some hefty debugging infrastructure that you get by using --enable-dbgutil switch during configure. Note that libraries from product and non-product builds are usually incompatible, so don't mix them in the same installation.
For available tools in such builds, have a look at the various DBG_foo macros in tools/debug.hxx, or, if you already are knowledgeable about this, let others participate by writing your knowledge down here.
To actually fire up the debug settings dialog, press
Writer-specific hints
It silently fails to load my word file
Caolan suggests: put breakpoints in ww8par.cxx top and tail of SwWW8ImplReader::?LoadDoc, and confirm that the document gets as far as the import filter.
A handy human place to put a breakpoint is in SwWW8ImplReader::?ReadPlainChars, you can see chunks of text as they are read in. Alternatively SwWW8ImplReader::?AppendTxtNode as each paragraph is inserted.
Dumping SfxItemSet objects:
define dump_pSfxItemSet
printf "count=%i\n", $arg0->_nCount
set $is_i=0
set $is_k=0
while($arg0->_pWhichRanges[$is_i]!=0)
printf "[%i; %i]\n", $arg0->_pWhichRanges[$is_i], $arg0->_pWhichRanges[$is_i+1]
set $is_j=$arg0->_pWhichRanges[$is_i]
while($is_j<=$arg0->_pWhichRanges[$is_i+1])
if ($arg0->_aItems[$is_k]!=0)
printf "%i %i %p\n", $is_k, $is_j, $arg0->_aItems[$is_k]
end
set $is_j++
set $is_k++
end
set $is_i=$is_i+2
end
end
Dumping the nodes structure
This functions doesn't seem to be friendly with set print object or set print pretty.
define pIndent
set $level = $arg0
set $iLevel = 0
while ( $iLevel < $level )
printf "\t"
set $iLevel = $iLevel + 1
end
end
define pNodeType
if ($sw_node->nNodeType==1)
printf "ND_ENDNODE "
end
if ($sw_node->nNodeType==2)
printf "ND_STARTNODE "
end
if ($sw_node->nNodeType==6)
printf "ND_TABLENODE "
end
if ($sw_node->nNodeType==8)
printf "ND_TEXTNODE "
end
if ($sw_node->nNodeType==0x10)
printf "ND_GRFNODE "
end
if ($sw_node->nNodeType==0x20)
printf "ND_OLENODE "
end
if ($sw_node->nNodeType==0x38)
printf "ND_CONTENTNODE "
end
if ($sw_node->nNodeType==0x30)
printf "ND_NOTXTNODE "
end
if ($sw_node->nNodeType==0x42)
printf "ND_SECTIONNODE "
end
end
define dump_pSwUndo
set $su_i=0
while ($su_i<$arg0->nA)
set $su_n=((SwUndo**)($arg0->pData))[$su_i]
printf "%i %p %i\n", $su_i, $su_n, $su_n->nId
set $su_i++
end
end
define pNodesArr
set $sw_size = $arg0->nSize
set $iNodes = 0
set $indent = 0
while ( $iNodes++<$sw_size && $iNodes<255 )
set $sw_node=$arg0[$iNodes-1]
if ( $sw_node->nNodeType == 1 )
set $indent = $indent - 1
end
pIndent $indent
printf "%d ", $iNodes - 1
pNodeType
if ( $sw_node->nNodeType == 2 || $sw_node->nNodeType == 6 )
printf ", EoS: %d", $sw_node->GetStartNode( )->pEndOfSection->nOffset
set $indent = $indent + 1
end
if ( $sw_node->IsTxtNode( ) )
printf ", Text: "
set $sw_txt = $sw_node->GetTxtNode( )->aText
ptu $sw_txt
else
printf "\n"
end
end
end
Calc-specific hints
Excel Interop debugging
To dump the contents of binary MS Excel files while loading them into ?OpenOffice.org, first get a local copy of the code module "oox". Then:
- XLS files (BIFF2-BIFF8): define the environment variable
OOO_BIFFDUMPERpointing to file://..../oox/source/dump/biffdumper.ini (full path needed). Then runsoffice.bin foo.xlsand you should get a foo.xls.dump directory in the same directory with the debug data in it. The new directory will contain the complete storage structure with all original streams, and the decoded streams with ".dump" suffix. - XLSX, XLSM, XLSB files: define the environment variable
OOO_XLSBDUMPERpointing to file://..../oox/source/dump/xlsbdumper.ini (full path needed). Then runsoffice.bin foo.xlsb. XML streams will be pretty-printed, and known binary streams (e.g. the VBA project, and the streams used in XLSB format) are decoded. - also PPTX, PPTM files are supported: define the environment variable
OOO_PPTXDUMPERpointing to file://..../oox/source/dump/pptxdumper.ini (full path needed). Then runsoffice.bin foo.pptx. Note: this requires a debug build of theooxmodule. To easily get such a build, execute the following within yourscdirectory:
build -- killobj ; build debug=true
Impress-specific hints
Draw/Impress text edit debugging
When running a build configured with --enable-dbgutil, live edit mode in Draw/Impress text boxes has an extra debug hotkey: pressing
PPTX import
See the Excel Interop Debug above for information about OOO_PPTXDUMPER variable.