R devel - May 2002 - names(unlist(...)) may construct corrupt strings (PR#1524)

names(unlist(...)) seems to be able to construct corrupt strings
detected via: two identical strings behave different in paste
observed in RW1.4.1 and RW1.5.0
pure replication code after output

Best


Jens Oehlschlägel

> l <- names(unlist(list(aa = list(bb = 1))))
> l
[1] "aa.bb"
> # this is exactly "aa.bb"
> identical(l, "aa.bb")
[1] TRUE
> 
> # BUT 
> identical(paste("aa.bb", "this should be added"),
paste(l, "this should be
added"))
[1] FALSE
> 
> # this of course works
> paste("aa.bb", "this should be added")
[1] "aa.bb this should be added"
> 
> # BUT THIS FAILS
> paste(l, "this should be added")
[1] "aa.bb"



l <- names(unlist(list(aa = list(bb = 1))))
l
# this is exactly "aa.bb"
identical(l, "aa.bb")

# BUT 
identical(paste("aa.bb", "this should be added"), paste(l,
"this should be
added"))

# this of course works
paste("aa.bb", "this should be added")

# BUT THIS FAILS
paste(l, "this should be added")




--please do not edit the information below--

Version:
 platform = i386-pc-mingw32
 arch = i386
 os = mingw32
 system = i386, mingw32
 status = 
 major = 1
 minor = 5.0
 year = 2002
 month = 04
 day = 29
 language = R

Windows 2000 Professional (build 2195) Service Pack 1.0

Search Path:
 .GlobalEnv, package:ctest, Autoloads, package:base

-- 
GMX - Die Kommunikationsplattform im Internet.



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On Tue, 7 May 2002 oehl_list@gmx.de wrote:
> names(unlist(...)) seems to be able to construct corrupt strings
> detected via: two identical strings behave different in paste
> observed in RW1.4.1 and RW1.5.0
> pure replication code after output
>
> Best
>
>
> Jens Oehlschlägel
>
>
> > l <- names(unlist(list(aa = list(bb = 1))))
> > l
> [1] "aa.bb"
This is the same problem with do_paste that showed up with read.dta. If
you look at the C level, LENGTH() is 6 for l and 5 for "aa.bb".

In general we have the problem that a string has two ways of defining its
length:  LENGTH() and strlen()

Most functions use just one of these, but paste() uses LENGTH() to set up
the buffer and then strcpy() to copy into it. The string l has LENGTH 6,
but strlen 5, and the result from paste() is a string with a null as its
sixth character, which thus appears to be a five-character string.

Given that this is the second appearance of the problem perhaps do_paste()
should be changed instead of (as well as?) unlist().

	-thomas


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On Tue, 7 May 2002, Thomas Lumley wrote:
> On Tue, 7 May 2002 oehl_list@gmx.de wrote:
>
> > names(unlist(...)) seems to be able to construct corrupt strings
> > detected via: two identical strings behave different in paste
> > observed in RW1.4.1 and RW1.5.0
> > pure replication code after output
> >
> > Best
> >
> >
> > Jens Oehlschlägel
> >
> >
> > > l <- names(unlist(list(aa = list(bb = 1))))
> > > l
> > [1] "aa.bb"
>
> This is the same problem with do_paste that showed up with read.dta. If
> you look at the C level, LENGTH() is 6 for l and 5 for "aa.bb".
>
> In general we have the problem that a string has two ways of defining its
> length:  LENGTH() and strlen()
>
> Most functions use just one of these, but paste() uses LENGTH() to set up
> the buffer and then strcpy() to copy into it. The string l has LENGTH 6,
> but strlen 5, and the result from paste() is a string with a null as its
> sixth character, which thus appears to be a five-character string.
>
> Given that this is the second appearance of the problem perhaps do_paste()
> should be changed instead of (as well as?) unlist().
I'm fixing both.  The root bug is on line 334 of bind.c.

-- 
Brian D. Ripley,                  ripley@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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595


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