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I was revisiting Negating Regexes: Tips, Tools, And Tricks Of The Trade and caused perl to segfault with one of the patterns I tried. I reduced the pattern to he simplest form that still causes a problem. Tested with:

This is perl, v5.8.7 built for i486-linux-gnu-thread-multi
Characteristics of this binary (from libperl):
  Compile-time options: MULTIPLICITY USE_ITHREADS USE_LARGE_FILES
                        PERL_IMPLICIT_CONTEXT
[download]

This works:

  "1" =~ qr[(??{/^1/})]
[download]

This segfaults

  "<" =~ qr[(??{/^</})]
[download]

Segfault re=debug output:

Freeing REx: `","'
Compiling REx `(??{/^</})'
size 4 Got 36 bytes for offset annotations.
Compiling REx `^<'

size 4 Got 36 bytes for offset annotations.
first at 2
   1: BOL(2)
   2: EXACT <<>(4)
   4: END(0)
anchored `<' at 0 (checking anchored) anchored(BOL) minlen 1
Offsets: [4]
        1[1] 2[1] 0[0] 3[0]
first at 1
   1: LOGICAL[2](2)
   2: EVAL(4)
   4: END(0)
minlen 0 with eval
Offsets: [4]
        10[0] 10[0] 0[0] 11[0]
Matching REx `(??{/^</})' against `<'
  Setting an EVAL scope, savestack=15
   0 <> <<>               |  1:  LOGICAL[2]
   0 <> <<>               |  2:  EVAL
  re_eval 0x8153fe8
Guessing start of match, REx `^<' against `<'...
Guessed: match at offset 0
Matching REx `^<' against `<'
  Setting an EVAL scope, savestack=15
   0 <> <<>               |  1:  BOL
   0 <> <<>               |  2:  EXACT <<>
   1 <<> <>               |  4:  END
Match successful!
Compiling REx `1'
size 3 Got 28 bytes for offset annotations.
first at 1
   1: EXACT <1>(3)
   3: END(0)
anchored `1' at 0 (checking anchored isall) minlen 1
Offsets: [3]
        1[1] 0[0] 2[0]
Entering embedded `1'
  Setting an EVAL scope, savestack=21
   0 <> <<>               |  1:  EXACT <1>
                            failed...
Freeing REx: `"1"'
                          failed...
  Setting an EVAL scope, savestack=24
   1 <<> <>               |50339:  LOGICAL[2]
   1 <<> <>               |50340:  EVAL
[download]

Is this fixed in later perls?

In reply to regex bug in perl 5.8.7 by imp

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