On Tue, 6 May 2008, Duncan Murdoch wrote:
> On 06/05/2008 3:02 AM, pseudo wrote:
> > Dear all,
> >
> > When using gdb to debug my C code, I use R_PV to show the content of
> > SEXP variables:
> >
> > SEXP sexp; // it is a data.frame
> > SEXP colNames = getAttrib(sexp, R_NameSymbol);
> >
> > A strange thing is that after halting the program:
> >
> > (gdb) p R_PV(colNames)
> >
> > does not show the content of colNames. I am positive my code is right
> > because if I insert "PrintValue(colNames);" in the c code, it will
> > print the right value. My debug result shows that the variable
> > "colNames" failed the "isObject" call. I am not sure whether this is a
> > new feature or bug. Anyone can help?
>
> Are you sure that getAttrib has been called? Depending on the
> optimization level under which your code was compiled, instructions may
> be re-ordered. gdb may show the instruction pointer after that line,
> even though that line hasn't been run yet.
R_PV(sexp) only prints if isObject(sexp) is true, i.e., if it
is "internally classed". Try using Rf_PrintValue(colNames) from
the debugger.
src/main/print.c contains:
/* Print an S-expression using global options */
void PrintValue(SEXP s)
{
PrintValueEnv(s, R_GlobalEnv);
}
/* Ditto, but only for objects, for use in debugging */
void R_PV(SEXP s)
{
if(isObject(s)) PrintValueEnv(s, R_GlobalEnv);
}
and include/Internals.h has the usual add-Rf_ #define:
#define PrintValue Rf_PrintValue
----------------------------------------------------------------------------
Bill Dunlap
Insightful Corporation
bill at insightful dot com
360-428-8146
"All statements in this message represent the opinions of the author and do
not necessarily reflect Insightful Corporation policy or position."
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