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replace problem in mb_ereg(i)_replace

PHP patch internal

今まで放置していたのですが、ふと思い出したので。
mb_ereg(i)_replace関数で微妙な挙動に遭遇したのですが（皆さん）どうやって回避しているのだろうか。。。教えて欲しいっす！(>_<)

% cd /usr/local/src
% gzip -dc ./php-4.4.8.tar.gz | gtar xf -
% cd ./php-4.4.8
% ./configure \
--disable-all \
--without-mysql \
--enable-mbstring \
--enable-debug

% make
% cp sapi/cli/php /usr/local/src/php-4.4.8-cli1

% cd /usr/local/src
% gzip -dc ./php-5.2.5.tar.gz | gtar xf -
% cd ./php-5.2.5
% ./configure \
--disable-all \
--without-iconv \
--enable-mbstring \
--enable-debug

% make
% cp sapi/cli/php /usr/local/src/php-5.2.5-cli1

% cd /usr/local/src
% cat ./replace.php
<?php

  $STR = "price is <%price%>.";
  $BF  = "<%price%>";

  echo "----------------------------------------------".PHP_EOL;
  var_dump( PHP_VERSION );


  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\0";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\1";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\2";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\3";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\4";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\5";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\6";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\7";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\8";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

  echo "----------------------------------------------".PHP_EOL;
  $AF  = "\\9";
  var_dump( mb_ereg_replace(  $BF, $AF, $STR ) );
  var_dump( mb_eregi_replace( $BF, $AF, $STR ) );

?>

% ./php-4.4.8-cli1 ./replace.php
----------------------------------------------
string(5) "4.4.8"
----------------------------------------------
string(19) "price is <%price%>."
string(19) "price is <%price%>."
----------------------------------------------
string(12) "price is \1."
string(12) "price is \1."
----------------------------------------------
string(12) "price is \2."
string(12) "price is \2."
----------------------------------------------
string(12) "price is \3."
string(12) "price is \3."
----------------------------------------------
string(12) "price is \4."
string(12) "price is \4."
----------------------------------------------
string(12) "price is \5."
string(12) "price is \5."
----------------------------------------------
string(12) "price is \6."
string(12) "price is \6."
----------------------------------------------
string(12) "price is \7."
string(12) "price is \7."
----------------------------------------------
string(12) "price is \8."
string(12) "price is \8."
----------------------------------------------
string(12) "price is \9."
string(12) "price is \9."

% ./php-5.2.5-cli1 ./replace.php
----------------------------------------------
string(5) "5.2.5"
----------------------------------------------
string(19) "price is <%price%>."
string(19) "price is <%price%>."
----------------------------------------------
string(12) "price is \1."
string(12) "price is \1."
----------------------------------------------
string(12) "price is \2."
string(12) "price is \2."
----------------------------------------------
string(12) "price is \3."
string(12) "price is \3."
----------------------------------------------
string(12) "price is \4."
string(12) "price is \4."
----------------------------------------------
string(12) "price is \5."
string(12) "price is \5."
----------------------------------------------
string(12) "price is \6."
string(12) "price is \6."
----------------------------------------------
string(12) "price is \7."
string(12) "price is \7."
----------------------------------------------
string(12) "price is \8."
string(12) "price is \8."
----------------------------------------------
string(12) "price is \9."
string(12) "price is \9."

「\0」だけ置換されてないし。。。＿|￣|○
実装がどうなっているか確認。
バージョンに限らず発生しているという事は、この部分の制御は正規表現エンジン中ではなく、PHP内部で制御しているのでは。。。と思っていたら見事にビンゴ。

% cd /usr/local/src
% less -N ./php-4.4.8/ext/mbstring/php_mbregex.c

        〜 省略 〜

    519                         /* copy replacement and backrefs */
    520                         /* FIXME: this code (\\digit replacement) is not mbyte aware! */
    521                         i = 0;
    522                         p = replace;
    523                         while (i < replace_len) {
    524                                 n = -1;
    525                                 if (p[0] == '\\' && p[1] >= '0' && p[1] <= '9') {   /* ※１ */
    526                                         n = p[1] - '0';                             /* ※１ */
    527                                 }                                                   /* ※１ */
    528                                 if (n >= 0 && n < regs.num_regs) {                  /* ※２ */
    529                                         if (regs.beg[n] >= 0 && regs.beg[n] < regs.end[n] && regs.end[n] <= string_len) {
    530                                                 _php_mb_regex_strbuf_ncat(pdevice, (const unsigned char *)&string[regs.beg[n]], regs.end[n] - regs.beg[n]);
    531                                         }
    532                                         p += 2;
    533                                         i += 2;
    534                                 } else {
    535                                         _php_mb_regex_strbuf_ncat(pdevice, (const unsigned char *)p, 1);
    536                                         p++;
    537                                         i++;
    538                                 }
    539                         }

        〜 省略 〜

% less -N ./php-5.2.5/ext/mbstring/php_mbregex.c

        〜 省略 〜

    713                         /* copy replacement and backrefs */
    714                         i = 0;
    715                         p = replace;
    716                         while (i < replace_len) {
    717                                 int fwd = (int) php_mb_mbchar_bytes_ex(p, enc);
    718                                 n = -1;
    719                                 if ((replace_len - i) >= 2 && fwd == 1 &&
    720                                         p[0] == '\\' && p[1] >= '0' && p[1] <= '9') {   /* ※１ */
    721                                         n = p[1] - '0';                                 /* ※１ */
    722                                 }                                                       /* ※１ */
    723                                 if (n >= 0 && n < regs->num_regs) {                     /* ※２ */
    724                                         if (regs->beg[n] >= 0 && regs->beg[n] < regs->end[n] && regs->end[n] <= string_len) {
    725                                                 smart_str_appendl(pbuf, string + regs->beg[n], regs->end[n] - regs->beg[n]);
    726                                         }
    727                                         p += 2;
    728                                         i += 2;
    729                                 } else {
    730                                         smart_str_appendl(pbuf, p, fwd);
    731                                         p += fwd;
    732                                         i += fwd;
    733                                 }
    734                         }

        〜 省略 〜

「\」の次が「0」「1」「2」「3」「4」「5」「6」「7」「8」「9」であった場合は該当処理（※１）が実行される。。。と。
で、「regs.num_regs」が「1」になっていたので該当処理（※２）が実行される。。。と。「\0」の時だけ。＿|￣|○
危険を承知で該当処理（※２）に入らないよう修正してみる。暫定処置なのでパッチは手抜き。

% cd /usr/local/src
% cat ./php-4.4.8-php_mbregex.c.diff
--- php-4.4.8,orig/ext/mbstring/php_mbregex.c	2006-01-01 22:46:54.000000000 +0900
+++ php-4.4.8/ext/mbstring/php_mbregex.c	2008-03-31 10:12:08.000000000 +0900
@@ -523,7 +523,6 @@
 			while (i < replace_len) {
 				n = -1;
 				if (p[0] == '\\' && p[1] >= '0' && p[1] <= '9') {
-					n = p[1] - '0';
 				}
 				if (n >= 0 && n < regs.num_regs) {
 					if (regs.beg[n] >= 0 && regs.beg[n] < regs.end[n] && regs.end[n] <= string_len) {
% patch -p0 < ./php-4.4.8-php_mbregex.c.diff
patching file php-4.4.8/ext/mbstring/php_mbregex.c
% cd ./php-4.4.8
% make clean
% make
% cp sapi/cli/php /usr/local/src/php-4.4.8-cli2

% cd /usr/local/src
% cat ./php-5.2.5-php_mbregex.c.diff
--- php-5.2.5,orig/ext/mbstring/php_mbregex.c	2007-01-12 07:23:20.000000000 +0900
+++ php-5.2.5/ext/mbstring/php_mbregex.c	2008-03-31 10:12:28.000000000 +0900
@@ -718,7 +718,6 @@
 				n = -1;
 				if ((replace_len - i) >= 2 && fwd == 1 &&
 					p[0] == '\\' && p[1] >= '0' && p[1] <= '9') {
-					n = p[1] - '0';
 				}
 				if (n >= 0 && n < regs->num_regs) {
 					if (regs->beg[n] >= 0 && regs->beg[n] < regs->end[n] && regs->end[n] <= string_len) {
% patch -p0 < ./php-5.2.5-php_mbregex.c.diff
patching file php-5.2.5/ext/mbstring/php_mbregex.c
% cd ./php-5.2.5
% make clean
% make
% cp sapi/cli/php /usr/local/src/php-5.2.5-cli2

% cd /usr/local/src
% ./php-4.4.8-cli2 ./replace.php
----------------------------------------------
string(5) "4.4.8"
----------------------------------------------
string(12) "price is \0."
string(12) "price is \0."
----------------------------------------------
string(12) "price is \1."
string(12) "price is \1."
----------------------------------------------
string(12) "price is \2."
string(12) "price is \2."
----------------------------------------------
string(12) "price is \3."
string(12) "price is \3."
----------------------------------------------
string(12) "price is \4."
string(12) "price is \4."
----------------------------------------------
string(12) "price is \5."
string(12) "price is \5."
----------------------------------------------
string(12) "price is \6."
string(12) "price is \6."
----------------------------------------------
string(12) "price is \7."
string(12) "price is \7."
----------------------------------------------
string(12) "price is \8."
string(12) "price is \8."
----------------------------------------------
string(12) "price is \9."
string(12) "price is \9."

% ./php-5.2.5-cli2 ./replace.php
----------------------------------------------
string(5) "5.2.5"
----------------------------------------------
string(12) "price is \0."
string(12) "price is \0."
----------------------------------------------
string(12) "price is \1."
string(12) "price is \1."
----------------------------------------------
string(12) "price is \2."
string(12) "price is \2."
----------------------------------------------
string(12) "price is \3."
string(12) "price is \3."
----------------------------------------------
string(12) "price is \4."
string(12) "price is \4."
----------------------------------------------
string(12) "price is \5."
string(12) "price is \5."
----------------------------------------------
string(12) "price is \6."
string(12) "price is \6."
----------------------------------------------
string(12) "price is \7."
string(12) "price is \7."
----------------------------------------------
string(12) "price is \8."
string(12) "price is \8."
----------------------------------------------
string(12) "price is \9."
string(12) "price is \9."

とりあえず置換されるようになった。影響範囲（副作用）は不明。
オリジナルの実装者ではないので詳細は不明なのですが、こういう実装になっているのは何か理由があるのかしら。なんか、ありそう。
正規表現に詳しくないのでアレなんですが、replacementの「\0」って何か特別な意味を持っているのだろうか。
それにしても、そろそろmb_str_replace関数が欲しいなぁ。。。と思う、今日この頃。