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avoid exponential regex match for java and objc function names
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In the old regex

^[ \t]*(([ \t]*[A-Za-z_][A-Za-z_0-9]*){2,}[ \t]*\([^;]*)$
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

you can backtrack arbitrarily from [A-Za-z_0-9]* into [A-Za-z_], thus
causing an exponential number of backtracks.  Ironically it also causes
the regex not to work as intended; for example "catch" can match the
underlined part of the regex, the first repetition matching "c" and
the second matching "atch".

The replacement regex avoids this problem, because it makes sure that
at least a space/tab is eaten on each repetition.  In other words,
a suffix of a repetition can never be a prefix of the next repetition.

Signed-off-by: Paolo Bonzini <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>
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bonzini authored and gitster committed Jun 18, 2009
1 parent 9b7dc71 commit 959e2e6
Showing 1 changed file with 3 additions and 2 deletions.
5 changes: 3 additions & 2 deletions userdiff.c
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,8 @@ PATTERNS("html", "^[ \t]*(<[Hh][1-6][ \t].*>.*)$",
"[^<>= \t]+|[^[:space:]]|[\x80-\xff]+"),
PATTERNS("java",
"!^[ \t]*(catch|do|for|if|instanceof|new|return|switch|throw|while)\n"
"^[ \t]*(([ \t]*[A-Za-z_][A-Za-z_0-9]*){2,}[ \t]*\\([^;]*)$",
"^[ \t]*(([A-Za-z_][A-Za-z_0-9]*[ \t]+)+[A-Za-z_][A-Za-z_0-9]*[ \t]*\\([^;]*)$",
/* -- */
"[a-zA-Z_][a-zA-Z0-9_]*"
"|[-+0-9.e]+[fFlL]?|0[xXbB]?[0-9a-fA-F]+[lL]?"
"|[-+*/<>%&^|=!]="
Expand All @@ -25,7 +26,7 @@ PATTERNS("objc",
/* Objective-C methods */
"^[ \t]*([-+][ \t]*\\([ \t]*[A-Za-z_][A-Za-z_0-9* \t]*\\)[ \t]*[A-Za-z_].*)$\n"
/* C functions */
"^[ \t]*(([ \t]*[A-Za-z_][A-Za-z_0-9]*){2,}[ \t]*\\([^;]*)$\n"
"^[ \t]*(([A-Za-z_][A-Za-z_0-9]*[ \t]+)+[A-Za-z_][A-Za-z_0-9]*[ \t]*\\([^;]*)$\n"
/* Objective-C class/protocol definitions */
"^(@(implementation|interface|protocol)[ \t].*)$",
/* -- */
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