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* [Bug gdb/13465] New: typecasting in gdb python pretty-printer
@ 2011-12-01 19:53 eric at anholt dot net
2011-12-01 20:26 ` [Bug gdb/13465] " tromey at redhat dot com
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: eric at anholt dot net @ 2011-12-01 19:53 UTC (permalink / raw)
To: gdb-prs
http://sourceware.org/bugzilla/show_bug.cgi?id=13465
Bug #: 13465
Summary: typecasting in gdb python pretty-printer
Product: gdb
Version: 7.3
Status: NEW
Severity: enhancement
Priority: P2
Component: gdb
AssignedTo: unassigned@sourceware.org
ReportedBy: eric@anholt.net
Classification: Unclassified
Context:
In Mesa graphics drivers implemented in C, there are these Mesa core types
(struct gl_texture_object, struct gl_texture_image), which each driver creates
"subclasses" of by embedding that struct in their own struct as:
struct intel_texture_image {
struct gl_texture_image base;
struct intel_mipmap_tree *mt;
}
When debugging Mesa, we often have a pointer to a base type like struct
gl_texture_image, so to print the information we always want to see we have to
p *(struct intel_context *)tex_image.
What I want:
I'd like to be able to implement a python pretty-printer autoloaded based on my
driver's object file that can make a decision about what type to print one of
these base types as (either by looking at vtbl-like information in some
objects, or just by knowing that if you've got i965_dri.so loaded, every struct
gl_texture_image is a struct intel_texture_image). However, I'm told that
there isn't a way to do that today:
<tromey> so, we don't have a value-replacement facility
<tromey> that might be a nice addition
<xdje> replace the value where?
<tromey> he basically wants something like 'set print object on', that works
for his particular C case
<tromey> based on knowledge of his program
<tromey> without writing a full printer for the enclosing struct
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* [Bug gdb/13465] typecasting in gdb python pretty-printer
2011-12-01 19:53 [Bug gdb/13465] New: typecasting in gdb python pretty-printer eric at anholt dot net
@ 2011-12-01 20:26 ` tromey at redhat dot com
2011-12-02 12:14 ` pedro at codesourcery dot com
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: tromey at redhat dot com @ 2011-12-01 20:26 UTC (permalink / raw)
To: gdb-prs
http://sourceware.org/bugzilla/show_bug.cgi?id=13465
Tom Tromey <tromey at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |tromey at redhat dot com
--- Comment #1 from Tom Tromey <tromey at redhat dot com> 2011-12-01 20:24:51 UTC ---
I thought maybe this could be done by returning the
derived object in the printer's to_string method.
However, there is no way to circumvent the resulting
recursion in this case.
So, I think we need some new facility here.
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* [Bug gdb/13465] typecasting in gdb python pretty-printer
2011-12-01 19:53 [Bug gdb/13465] New: typecasting in gdb python pretty-printer eric at anholt dot net
2011-12-01 20:26 ` [Bug gdb/13465] " tromey at redhat dot com
@ 2011-12-02 12:14 ` pedro at codesourcery dot com
2011-12-14 16:29 ` dje at google dot com
2012-02-07 16:01 ` [Bug python/13465] " tromey at redhat dot com
3 siblings, 0 replies; 5+ messages in thread
From: pedro at codesourcery dot com @ 2011-12-02 12:14 UTC (permalink / raw)
To: gdb-prs
http://sourceware.org/bugzilla/show_bug.cgi?id=13465
Pedro Alves <pedro at codesourcery dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |pedro at codesourcery dot
| |com
--- Comment #2 from Pedro Alves <pedro at codesourcery dot com> 2011-12-02 12:13:32 UTC ---
I think there are ways to avoid the recursion. It's not a real replacement for
a value-replacement facility, but this works for me (based on py-prettyprint.py
in the testsuite):
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test.c:
struct base
{
int a;
};
struct sub
{
struct base base;
int b;
};
struct base b = { 1 };
struct sub s = { { 1 }, 2};
int
main (int argc, char *argv)
{
return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
baseprinter.py:
import re
import gdb
class pp_base:
def __init__(self, val):
self.val = val
ptrtype = gdb.lookup_type('struct sub')
self.castval = val.address.cast(ptrtype.pointer()).dereference ()
def to_string(self):
disable_lookup_function ()
r = str(self.castval)
enable_lookup_function ()
return r
def lookup_function (val):
"Look-up and return a pretty-printer that can print val."
# Get the type.
type = val.type
# If it points to a reference, get the reference.
if type.code == gdb.TYPE_CODE_REF:
type = type.target ()
# Get the unqualified type, stripped of typedefs.
type = type.unqualified ().strip_typedefs ()
# Get the type name.
typename = type.tag
if typename == None:
return None
# Iterate over local dictionary of types to determine
# if a printer is registered for that type. Return an
# instantiation of the printer if found.
for function in pretty_printers_dict:
if function.match (typename):
return pretty_printers_dict[function] (val)
# Cannot find a pretty printer. Return None.
return None
def disable_lookup_function ():
lookup_function.enabled = False
def enable_lookup_function ():
lookup_function.enabled = True
def register_pretty_printers ():
pretty_printers_dict[re.compile ('^struct base$')] = pp_base
pretty_printers_dict[re.compile ('^base$')] = pp_base
pretty_printers_dict = {}
register_pretty_printers ()
gdb.pretty_printers.append (lookup_function)
$ gdb -nx -q ~/printer -ex "set python print-stack on" -ex "python execfile
('/home/pedro/printer.py')"
Reading symbols from /home/pedro/printer...done.
(gdb) p b
$1 = {base = {a = 1}, b = 1}
(gdb) p /r b
$2 = {a = 1}
(gdb)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
That is, disable the printer lookup function of the baseclass when you want to
print it raw.
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^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug gdb/13465] typecasting in gdb python pretty-printer
2011-12-01 19:53 [Bug gdb/13465] New: typecasting in gdb python pretty-printer eric at anholt dot net
2011-12-01 20:26 ` [Bug gdb/13465] " tromey at redhat dot com
2011-12-02 12:14 ` pedro at codesourcery dot com
@ 2011-12-14 16:29 ` dje at google dot com
2012-02-07 16:01 ` [Bug python/13465] " tromey at redhat dot com
3 siblings, 0 replies; 5+ messages in thread
From: dje at google dot com @ 2011-12-14 16:29 UTC (permalink / raw)
To: gdb-prs
http://sourceware.org/bugzilla/show_bug.cgi?id=13465
dje at google dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |dje at google dot com
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* [Bug python/13465] typecasting in gdb python pretty-printer
2011-12-01 19:53 [Bug gdb/13465] New: typecasting in gdb python pretty-printer eric at anholt dot net
` (2 preceding siblings ...)
2011-12-14 16:29 ` dje at google dot com
@ 2012-02-07 16:01 ` tromey at redhat dot com
3 siblings, 0 replies; 5+ messages in thread
From: tromey at redhat dot com @ 2012-02-07 16:01 UTC (permalink / raw)
To: gdb-prs
http://sourceware.org/bugzilla/show_bug.cgi?id=13465
Tom Tromey <tromey at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|gdb |python
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end of thread, other threads:[~2012-02-07 16:01 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2011-12-01 19:53 [Bug gdb/13465] New: typecasting in gdb python pretty-printer eric at anholt dot net
2011-12-01 20:26 ` [Bug gdb/13465] " tromey at redhat dot com
2011-12-02 12:14 ` pedro at codesourcery dot com
2011-12-14 16:29 ` dje at google dot com
2012-02-07 16:01 ` [Bug python/13465] " tromey at redhat dot com
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