Provide --enable-asan and --disable-asan to toggle address sanitizer.

Since we are currently pre-alpha I decided to enable it by default
so we as devs don't forget to do so :)

configure

@@ -625,6 +625,7 @@ ac_includes_default="\
 ac_subst_vars='LTLIBOBJS
 LIBOBJS
 UNRLINCDIR
+IRCDLIBS
 URL
 PTHREAD_CFLAGS
 PTHREAD_LIBS
@@ -673,7 +674,6 @@ HARDEN_BINCFLAGS
 HARDEN_LDFLAGS
 HARDEN_CFLAGS
 MKPASSWDLIBS
-IRCDLIBS
 OBJEXT
 EXEEXT
 ac_ct_CC
@@ -764,6 +764,7 @@ with_system_cares
 enable_ssl
 enable_dynamic_linking
 enable_werror
+enable_asan
 enable_libcurl
 '
       ac_precious_vars='build_alias
@@ -1421,6 +1422,8 @@ Optional Features:
                           rather than dynamically (noone knows if disabling
                           dynamic linking actually does anything or not)
   --enable-werror         Turn compilation warnings into errors (-Werror)
+  --disable-asan          Disable address sanitizer and other debugging
+                          options
   --enable-libcurl=DIR    enable libcurl (remote include) support
 
 Optional Packages:
@@ -3972,7 +3975,6 @@ fi
 
 
 
-
 # We want to check for compiler flag support, but there is no way to make
 # clang's "argument unused" warning fatal.  So we invoke the compiler through a
 # wrapper script that greps for this message.
@@ -8773,6 +8775,15 @@ else
 fi
 
 
+
+# Check whether --enable-asan was given.
+if test "${enable_asan+set}" = set; then :
+  enableval=$enable_asan; ac_cv_asan="no"
+else
+  ac_cv_asan="yes"
+fi
+
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking if FD_SETSIZE is large enough to allow $ac_fd file descriptors" >&5
 $as_echo_n "checking if FD_SETSIZE is large enough to allow $ac_fd file descriptors... " >&6; }
 cat confdefs.h - <<_ACEOF >conftest.$ac_ext
@@ -10153,6 +10164,13 @@ if test "$ac_cv_werror" = "yes" ; then
 	CFLAGS="$CFLAGS -Werror"
 fi
 
+if test "$ac_cv_asan" = "yes" ; then
+	CFLAGS="$CFLAGS -O0 -fno-inline -fsanitize=address -fno-omit-frame-pointer -DNOCLOSEFD"
+	IRCDLIBS="-fsanitize=address $IRCDLIBS"
+fi
+
+
+
 
 
 ac_config_files="$ac_config_files Makefile src/Makefile src/modules/Makefile src/modules/chanmodes/Makefile src/modules/usermodes/Makefile src/modules/snomasks/Makefile src/modules/extbans/Makefile src/modules/cap/Makefile src/modules/third/Makefile unrealircd"

configure.ac

@@ -85,7 +85,6 @@ AC_CHECK_LIB(nsl, inet_ntoa,
 AC_CHECK_LIB(crypto, RAND_egd,
 		AC_DEFINE(HAVE_RAND_EGD, 1, [Define if the libcrypto has RAND_egd]))
 
-AC_SUBST(IRCDLIBS)
 AC_SUBST(MKPASSWDLIBS)
 
 dnl HARDENING START
@@ -712,6 +711,18 @@ AC_ARG_ENABLE([werror],
   [ac_cv_werror="$enableval"],
   [ac_cv_werror="no"])
 
+dnl AC_ARG_ENABLE([asan],
+dnl   [AS_HELP_STRING([--enable-asan],
+dnl     [Enable address sanitizer and other debugging options, not recommended for production servers!])],
+dnl   [ac_cv_asan="$enableval"],
+dnl   [ac_cv_asan="no"])
+
+AC_ARG_ENABLE([asan],
+  [AS_HELP_STRING([--disable-asan],
+    [Disable address sanitizer and other debugging options])],
+  [ac_cv_asan="no"],
+  [ac_cv_asan="yes"])
+
 AC_MSG_CHECKING([if FD_SETSIZE is large enough to allow $ac_fd file descriptors])
 AC_COMPILE_IFELSE([
 #include <sys/types.h>
@@ -970,6 +981,14 @@ if test "$ac_cv_werror" = "yes" ; then
 	CFLAGS="$CFLAGS -Werror"
 fi
 
+dnl Address sanitizer build
+if test "$ac_cv_asan" = "yes" ; then
+	CFLAGS="$CFLAGS -O0 -fno-inline -fsanitize=address -fno-omit-frame-pointer -DNOCLOSEFD"
+	IRCDLIBS="-fsanitize=address $IRCDLIBS"
+fi
+
+AC_SUBST(IRCDLIBS)
+
 AC_SUBST(UNRLINCDIR)
 
 AC_CONFIG_FILES([Makefile