build: enable building fuzz tests by default

fixes bitcoin#19388

Changes configure's '--enable-fuzz' flag to '--disable-fuzz'.
Enables building fuzz tests by default.
Enables -fsanitize=fuzzer by default.

Signed-off-by: willcl-ark <will8clark@gmail.com>

configure.ac

@@ -160,10 +160,10 @@ AC_ARG_ENABLE([extended-functional-tests],
     [use_extended_functional_tests=no])
 
 AC_ARG_ENABLE([fuzz],
-    AS_HELP_STRING([--enable-fuzz],
-    [enable building of fuzz targets (default no). enabling this will disable all other targets]),
+    AS_HELP_STRING([--disable-fuzz],
+    [disable building of fuzz targets (default is to compile)]),
     [enable_fuzz=$enableval],
-    [enable_fuzz=no])
+    [enable_fuzz=yes])
 
 AC_ARG_WITH([qrencode],
   [AS_HELP_STRING([--with-qrencode],
@@ -269,9 +269,16 @@ AC_ARG_ENABLE([debug],
 dnl Enable different -fsanitize options
 AC_ARG_WITH([sanitizers],
     [AS_HELP_STRING([--with-sanitizers],
-                    [comma separated list of extra sanitizers to build with (default is none enabled)])],
+                    [comma separated list of extra sanitizers to build with (default is 'fuzzer' unless --disable-fuzzer is set)])],
     [use_sanitizers=$withval])
 
+dnl if fuzz testing is enabled and user didn't set -fsanitize, set it to "fuzzer"
+if test "x$enable_fuzz" = xyes; then
+    if test "x$use_sanitizers" = x; then
+      use_sanitizers=fuzzer
+    fi
+fi
+
 dnl Enable gprof profiling
 AC_ARG_ENABLE([gprof],
     [AS_HELP_STRING([--enable-gprof],
@@ -1112,28 +1119,10 @@ AC_SUBST(LEVELDB_CPPFLAGS)
 AC_SUBST(LIBLEVELDB)
 AC_SUBST(LIBMEMENV)
 
-dnl enable-fuzz should disable all other targets
-if test "x$enable_fuzz" = "xyes"; then
-  AC_MSG_WARN(enable-fuzz will disable all other targets)
-  build_bitcoin_utils=no
-  build_bitcoin_cli=no
-  build_bitcoin_tx=no
-  build_bitcoin_wallet=no
-  build_bitcoind=no
-  build_bitcoin_libs=no
-  bitcoin_enable_qt=no
-  bitcoin_enable_qt_test=no
-  bitcoin_enable_qt_dbus=no
-  enable_wallet=no
-  use_bench=no
-  use_upnp=no
-  use_zmq=no
-else
-  BITCOIN_QT_INIT
+BITCOIN_QT_INIT
 
-  dnl sets $bitcoin_enable_qt, $bitcoin_enable_qt_test, $bitcoin_enable_qt_dbus
-  BITCOIN_QT_CONFIGURE
-fi
+dnl sets $bitcoin_enable_qt, $bitcoin_enable_qt_test, $bitcoin_enable_qt_dbus
+BITCOIN_QT_CONFIGURE
 
 if test x$enable_wallet != xno; then
     dnl Check for libdb_cxx only if wallet enabled
@@ -1689,9 +1678,7 @@ if test x$bitcoin_enable_qt != xno; then
 fi
 echo "  with zmq      = $use_zmq"
 echo "  with test     = $use_tests"
-if test x$use_tests != xno; then
-    echo "    with fuzz   = $enable_fuzz"
-fi
+echo "  with fuzz     = $enable_fuzz"
 echo "  with bench    = $use_bench"
 echo "  with upnp     = $use_upnp"
 echo "  use asm       = $use_asm"