Re: Displaying Custom Data Types in Debugger
Re: Displaying Custom Data Types in Debugger
- Subject: Re: Displaying Custom Data Types in Debugger
- From: Michael Rice <email@hidden>
- Date: Tue, 19 Jul 2005 18:43:54 -0500
On Jul 19, 2005, at 3:35 PM, Jim Ingham wrote:
On Jul 18, 2005, at 6:43 PM, Michael Rice wrote:
On Jul 18, 2005, at 6:44 PM, Jim Ingham wrote:
On Jul 18, 2005, at 4:33 PM, Michael Rice wrote:
On Jul 18, 2005, at 6:50 AM, Graham Westlake wrote:
On 16 Jul 2005, at 21:40, Chris Espinosa wrote:
You write a simple .c file that #includes " /Developer/
Applications/Xcode.app/Contents/PlugIns/
GDBMIDebugging.xcplugin/Contents/Headers/
DataFormatterPlugin.h", and a function that returns a char *
given a pointer to your Unicode string. Compile that into a
plugin that's structured like the CarbonDataFormatter.bundle,
and put in the plist the expression that calls your function.
Because to return a char * from your Unicode string you
probably have to allocate memory temporarily, you use the ID
passed in the expression and pass it to the _pbxgdb_allocator
(size, ID) function to allocate space for the char *. Xcode
will free this memory when your variable goes out of scope.
I've followed these instructions while attempting to write a
plugin to display the contents of a C++ class, but I'm not
having much luck - GDB crashes when I try to view my variable.
One necessary change I've made is to compile my plugin code as C
++; is this likely to be causing a problem? I've tried
declaring the formatting function as extern "C" but it hasn't
helped. Also, how is my C++ variable passed to the formatting
function?
I'm trying to do the same. I have an instance of a C++ class
that I need to display as a string. I've declared my interface
function in a .cpp file as:
char* MyObjectToCString(MyObject* data, int ID);
and the custom data format (in my bundle's
CustomDataViews.plist) as:
{MyObjectToCString($VAR, $ID)}
All I see in the debugger is {MyObjectToCString($VAR, $ID)},
which I'm taking to mean that it can't find my interface
function. I've tried defining the interface function in an
'extern "C"' block, but that didn't help. I used 'otool' to look
inside the CarbonDataFormatters and it shows that there are
mangled names in there, so I don't think it's required to use
"C" linkage.
Michael
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Xcode-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
40apple.com
This email sent to email@hidden
The data formatter code is running in the target program, so you
should be able to use the debugger on it too... Just make sure
you build your data formatter with debug info.
You can use the Shared Libraries list (Debugger->Tools->Shared
Libraries) to make sure your bundle got loaded.
Then if in the console you do:
(gdb) break MyObjectToCString
When Xcode calls your introspection function gdb will break
there. It might complain a bit about hitting a breakpoint while
running code in the inferior or something like that. But you
will anyway be able to debug the introspection function, make
sure it's getting reasonable behavior, and make sure it's setting
the output data correctly...
Jim
Jim -
Thanks for the info. I've progressed a little bit. I've verified
that my data formatter function is getting called (I've been able
to step into it in the debugger). It returns a string, allocated
using _pbxgdb_plugin_functions->message(), but the string itself
is not displayed in the Summary column, only the address of the
string. If I open the Expressions view and add '(char*)0x1621fb0',
where 0x1621fb0 is the address displayed in the Summary column,
and then double click the item in the Expressions view, it
displays the string I'm returning from my data formatter.
My data formatter function is defined as:
char* MyObjectToCString(MyObject*, int ID);
and my formatter spec is:
{(char *)MyObjectToCString(&$VAR, $ID)}
I'm using C++ linkage for my formatter function and the debugger
is able to resolve my function fine.
Any ideas how I can get the debugger to display the string instead
of the address?
Michael
I think you need to use:
{(char *)MyObjectToCString(&$VAR, $ID)}:s
For any expression that you use as a data formatter, you have the
option to display the VALUE of that expression, or the SUMMARY
field of that expression. In this case, the value of an expression
of type "char *" is it's pointer address, and it's summary is the
actual string value.
The default is to use the value. So you need to specify that you
want to use the summary, instead. You do that by putting :s after
the expression...
Jim
Awesome, that did the trick.
Thanks for the excellent help.
Michael
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Xcode-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden