[Rd] gsub(*, perl=TRUE) bug incl. seg.fault (PR#7108)

[Prof Brian Ripley]

I presume this was in R 1.9.1?

It seems that this was something I had already fixed (from another
symptom) and not been able to commit because the CVS archive was down.

I have now fixed it in R 1.9.1 patched and R-devel, and put a regression
test into the latter.

Brian

On Sat, 17 Jul 2004 maechler at stat.math.ethz.ch wrote:

> Experimenting a bit further, I've "found" the following
> 
> 1) the problem seems only gsub(), not sub()
> 
>   > sub(" ", "", "b c + d | a * b", perl=TRUE)
>   [1] "bc + d | a * b"
>   > gsub(" ", "", "b c + d | a * b", perl=TRUE)
>   NULL
> 
> 2) only if perl = TRUE, not otherwise
> 
> 3) Also modifying the replacement string only slightly leads to a
>   different (correct instead of bug) result:
> 
>   > gsub(" ", "", "bc + d | a * b", perl=TRUE)
>   [1] "bc+d|a*b"
>   > gsub(" ", "", "b c + d | a *", perl=TRUE)
>   [1] "bc+d|a*"
>   > gsub(" ", "", "b c + d | b", perl=TRUE)
>   [1] "bc+d|b"
> 
> Whereas those give the bug as well :
> 
>   > gsub(" ", "", "b : : d : a : b", perl=TRUE)
>   NULL
>   > gsub(" ", "", "b : : : : a : b", perl=TRUE)
>   NULL
>   > gsub(" ", "", "b : : : : : : b", perl=TRUE)
>   NULL
>   > gsub(" ", "", "a : : : : : : a", perl=TRUE)
>   NULL
> but not this
>   > gsub(" ", "", "b : : : : : : a", perl=TRUE)
>   [1] "b::::::a"
> 
> But it's even worse :
> 
>   > gsub(" ", "", "a: 12345 :a", perl=TRUE)
> 
>   -> segmentation fault
> 
> and from "R -d gdb" :
> 
>     > gsub(" ", "", "a: 12345 :a", perl=TRUE)
> 
>     Program received signal SIGSEGV, Segmentation fault.
>     hashIndex (symbol=0x8fd0060, table=0x823f2b8) at
>     ../../../R/src/main/envir.c:599
>     599	  if( !HASHASH(c) ) {
>     (gdb) bt
>     #0  hashIndex (symbol=0x8fd0060, table=0x823f2b8)
> 	at ../../../R/src/main/envir.c:599
>     #1  0x080b145d in R_GetGlobalCache (symbol=0x1)
> 	at ../../../R/src/main/envir.c:656
>     #2  0x080b1ac1 in findGlobalVar (symbol=0x8fd0060)
> 	at ../../../R/src/main/envir.c:923
>     #3  0x080b8873 in Rf_eval (e=0x823f2b8, rho=0x823f014)
> 	at ../../../R/src/main/eval.c:329
>     #4  0x080b88c9 in Rf_eval (e=0x8fd1e60, rho=0x821e540)
> 	at ../../../R/src/main/eval.c:354
>     #5  0x080e1e0e in GetObject (cptr=0xbfffd400)
> 	at ../../../R/src/main/objects.c:88
>     #6  0x080e2a3b in do_usemethod (call=0x84eb084, op=0x823be78, args=0x84eb0a0, 
> 	env=0x8fd1df0) at ../../../R/src/main/objects.c:381
>     #7  0x080b8c33 in Rf_eval (e=0x84eb084, rho=0x8fd1df0)
> 	at ../../../R/src/main/eval.c:375
>     #8  0x080b8f48 in Rf_applyClosure (call=0x8fd1eb4, op=0x84eafa4, 
> 	arglist=0x8fd1e44, rho=0x823f014, suppliedenv=0x821e540)
> 	at ../../../R/src/main/eval.c:559
>     #9  0x080b89bf in Rf_eval (e=0x8fd1eb4, rho=0x823f014)
> 	at ../../../R/src/main/eval.c:410
>     #10 0x0811b0f3 in Rf_PrintValueEnv (s=0x8fd1eb4, env=0x823f014)
> 	at ../../../R/src/main/print.c:775
>     #11 0x080d55f1 in Rf_ReplIteration (rho=0x823f014, savestack=150798432, 
> 	browselevel=1, state=0x823f014) at ../../../R/src/main/main.c:254
>     #12 0x080d578d in R_ReplConsole (rho=0x823f014, savestack=0, browselevel=0)
> 	at ../../../R/src/main/main.c:298
>     #13 0x080d60d0 in run_Rmainloop () 
>         at ../../../R/src/main/main.c:656
>     #14 0x08147e90 in main (ac=150798432, av=0x8fd0060)
> 	at ../../../R/src/unix/system.c:99
>     #15 0x42017589 in __libc_start_main () from /lib/i686/libc.so.6
> 
> (which is not directly helpful since  src/main/pcre.c  (where
> the C source for gsub(*, perl=TRUE) resides)  isn't mentioned above.
> 
> Must be a memory allocation / mismatch / end_of_string problem
> somewhere.
> 
> Martin Maechler, ETH Zurich
> 
> ______________________________________________
> R-devel at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-devel
> 
> 

-- 
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)
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