[Rd] Viewing R objects in gdb

Duncan Murdoch murdoch at stats.uwo.ca
Wed Jun 29 20:30:12 CEST 2005

On 6/29/2005 2:06 PM, Luke Tierney wrote:
> On Wed, 29 Jun 2005, Duncan Murdoch wrote:
>> I'm trying to track down a bug in some experimental code, where an
>> object's attribute is getting messed up.  This means I'd like to examine
>> R objects while within gdb.
>> One of the things I'd like to do is to examine the names of all the
>> attributes.  This is exactly what an example in the R Extensions manual
>> section 4.11.2 "Inspecting R objects when debugging" does, but the code
>> there doesn't work, presumably because the R internals have changed
>> since it was written.
>> Specifically, I get
>> (gdb) p $a->u.listsxp.tagval->u.symsxp.pname->u.vecsxp.type.c
>> Error: There is no member named vecsxp.
> Something like this I think (untested):
>          p ((VECSEXP)$a->u.listsxp.tagval->u.symsxp.pname)->vecsxp.type.c

That gets the typecast right, but now I have the problem that currently 
vecsxp doesn't have a type member:

(gdb) p ((VECSEXP)$a->u.listsxp.tagval->u.symsxp.pname)->vecsxp.type.c
Error: There is no member named type.

(gdb) p ((VECSEXP)$a->u.listsxp.tagval->u.symsxp.pname)->vecsxp
$1 = {length = 5, truelength = 6957219}

I guess I need to write a function that uses the macros to extract the 
data (since gdb doesn't see the macros).  Or do we already have one?

Duncan Murdoch

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