avoid exponential regex match for java and objc function names

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 <bonzini@gnu.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/userdiff.c b/userdiff.c
index d556da975197a718979575864e37c2b9b9f3327a..57529ae63d49826952b29860b3d4106b60250c7b 100644 (file)
--- a/userdiff.c
+++ b/userdiff.c
@@ -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]*\\([^;]*)$",
+        /* -- */
         "[a-zA-Z_][a-zA-Z0-9_]*"
         "|[-+0-9.e]+[fFlL]?|0[xXbB]?[0-9a-fA-F]+[lL]?"
         "|[-+*/<>%&^|=!]="
@@ -25,7 +26,7 @@ PATTERNS("objc",
         /* Objective-C methods */
         "^[ \t]*([-+][ \t]*\\([ \t]*[A-Za-z_][A-Za-z_0-9* \t]*\\)[ \t]*[A-Za-z_].*)$\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].*)$",
         /* -- */