[Rd] Bug in parse(text = <long polynom>) (PR#7022)

[Prof Brian Ripley]

On 25 Jun 2004, Peter Dalgaard wrote:

> maechler at stat.math.ethz.ch writes:
> 
> > Merci beaucoup, Jean,
> > for the bug report -- which I'm no "completeing" to R-bugs
> 
> But you're still requiring library(polynom) for triggering the bug. If
> we are to be sure that it is not a bug in that package 

There seems to be in that it is not using the R code from `S Programming' 
p.95, according to the original report.

> but a bug in R,
> you need to include the definition of at least polynomial() with the
> instructions to reproduce the effect...
> 
> [snip]
> > library(polynom)
> > 
> > x <- polynomial()
> > z <- (1+x)^100
> > zh <- horner(z)

Hmm, horner is not in the package!   It is a function internal to 
as.function.polynomial.

as.function(z) segfaults at

#0  R_TextBufferGetc (txtb=0xffda00)
    at /users/ripley/R/cvs/R-devel/src/main/iosupport.c:232
#1  0x080c7623 in text_getc () at ./gram.y:1011
#2  0x080c6eed in xxgetc () at ./gram.y:291
#3  0x080c7bc5 in token () at ./gram.y:1496
#4  0x080c85c5 in Rf_yylex () at ./gram.y:1894
#5  0x080c8bef in Rf_yyparse () at /usr/share/bison/bison.simple:573
#6  0x080c997e in R_Parse1 (status=0xbfffda58) at ./gram.y:941
#7  0x080c9aad in R_Parse (n=-1, status=0xbfffda58) at ./gram.y:1076
#8  0x080c9c1e in R_ParseVector (text=0xffffffff, n=-1, status=0xffffffff)
    at ./gram.y:1153
#9  0x0813c3d9 in do_parse (call=0x8500c00, op=0xffffffff, args=0x84fb898,
    env=0x8ed385c) at /users/ripley/R/cvs/R-devel/src/main/source.c:68

so that's definitely a bug in R. It is being asked to parse a very long
line and a highly-nested expression.  I suspect the latter is the problem.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595