a R_PV problem
Thanks for the pointer, and the problem solved. I double checked that Rf_PrintValue works when the option "unwindonsignal" is turned on in gdb. I also found that without "set unwindonsignal on", both "p Rf_PrintValue(colNames)" and "p R_PV(colNames)" could result in SIGTRAP or SIGSEGV sometimes. But not sure what caused the signal and why... because if I stepped into these functions, nothing would happen. Thanks, Gang
On Tue, May 6, 2008 at 8:30 AM, Bill Dunlap <bill at insightful.com> wrote:
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."