Revert "Remove the now obsolete regex_posix module".

The C++ SG16 has decided to obsolete std::regex because they
think its broken and don't want to fix it so this module will
probably outlive the regex_stdlib one. 🙄

This reverts commit e1dda3396c64f66b5889f72b65759251fab549ac.

configure

@@ -349,6 +349,7 @@ if (prompt_bool $interactive, $question, 0) {
 		'm_mysql.cpp'           => 'mysql_config --version',
 		'm_pgsql.cpp'           => 'pg_config --version',
 		'm_regex_pcre.cpp'      => 'pcre-config --version',
+		'm_regex_posix.cpp'     => undef,
 		'm_regex_re2.cpp'       => 'pkg-config --exists re2',
 		'm_regex_tre.cpp'       => 'pkg-config --exists tre',
 		'm_sqlite3.cpp'         => 'pkg-config --exists sqlite3',

docs/conf/modules.conf.example

@@ -839,6 +839,8 @@
 # glob   - Glob patterns, provided via regex_glob.                    #
 # pcre   - PCRE regexps, provided via regex_pcre, needs libpcre.      #
 # tre    - TRE regexps, provided via regex_tre, requires libtre.      #
+# posix  - POSIX regexps, provided via regex_posix, not available     #
+#          on Windows, no dependencies on other operating systems.    #
 # stdlib - stdlib regexps, provided via regex_stdlib, see comment     #
 #          at the <module> tag for info on availability.              #
 #                                                                     #
@@ -1714,6 +1716,15 @@
 # to compile and load this module.
 #<module name="regex_re2">
 
+#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#
+# Regular expression provider for POSIX regular expressions.
+# You shouldn't need any additional libraries on a POSIX-compatible
+# system (i.e.: any Linux, BSD, but not Windows). You must have at
+# least 1 provider loaded to use the filter or R-line modules.
+# On POSIX-compliant systems, regex syntax can be found by using the
+# command: 'man 7 regex'.
+#<module name="regex_posix">
+
 #-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#-#
 # Regular expression provider for C++11 std::regex regular expressions.
 #<module name="regex_stdlib">

src/modules/extra/m_regex_posix.cpp

@@ -0,0 +1,98 @@
+/*
+ * InspIRCd -- Internet Relay Chat Daemon
+ *
+ *   Copyright (C) 2013 Sadie Powell <sadie@witchery.services>
+ *   Copyright (C) 2012-2013 Attila Molnar <attilamolnar@hush.com>
+ *   Copyright (C) 2012 Robby <robby@chatbelgie.be>
+ *   Copyright (C) 2009-2010 Daniel De Graaf <danieldg@inspircd.org>
+ *   Copyright (C) 2009 Uli Schlachter <psychon@inspircd.org>
+ *   Copyright (C) 2008 Thomas Stagner <aquanight@inspircd.org>
+ *
+ * This file is part of InspIRCd.  InspIRCd is free software: you can
+ * redistribute it and/or modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation, version 2.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#include "inspircd.h"
+#include "modules/regex.h"
+#include <sys/types.h>
+#include <regex.h>
+
+class POSIXRegex : public Regex
+{
+	regex_t regbuf;
+
+ public:
+	POSIXRegex(const std::string& rx, bool extended) : Regex(rx)
+	{
+		int flags = (extended ? REG_EXTENDED : 0) | REG_NOSUB;
+		int errcode;
+		errcode = regcomp(&regbuf, rx.c_str(), flags);
+		if (errcode)
+		{
+			// Get the error string into a std::string. YUCK this involves at least 2 string copies.
+			std::string error;
+			char* errbuf;
+			size_t sz = regerror(errcode, &regbuf, NULL, 0);
+			errbuf = new char[sz + 1];
+			memset(errbuf, 0, sz + 1);
+			regerror(errcode, &regbuf, errbuf, sz + 1);
+			error = errbuf;
+			delete[] errbuf;
+			regfree(&regbuf);
+			throw RegexException(rx, error);
+		}
+	}
+
+	~POSIXRegex()
+	{
+		regfree(&regbuf);
+	}
+
+	bool Matches(const std::string& text) override
+	{
+		return (regexec(&regbuf, text.c_str(), 0, NULL, 0) == 0);
+	}
+};
+
+class PosixFactory : public RegexFactory
+{
+ public:
+	bool extended;
+	PosixFactory(Module* m) : RegexFactory(m, "regex/posix") {}
+	Regex* Create(const std::string& expr) override
+	{
+		return new POSIXRegex(expr, extended);
+	}
+};
+
+class ModuleRegexPOSIX : public Module
+{
+	PosixFactory ref;
+
+ public:
+	ModuleRegexPOSIX() : ref(this)
+	{
+	}
+
+	Version GetVersion() override
+	{
+		return Version("Regex Provider Module for POSIX Regular Expressions", VF_VENDOR);
+	}
+
+	void ReadConfig(ConfigStatus& status) override
+	{
+		ref.extended = ServerInstance->Config->ConfValue("posix")->getBool("extended");
+	}
+};
+
+MODULE_INIT(ModuleRegexPOSIX)