Rust: add 'debug' feature

The 'debug' feature is enabled if suricata was configured with the
--enabled-debug' flag.
If enabled, the SCLogDebug format and calls the logging function as
usual. Otherwise, this macro is a no-op (similarly to the C code).

rust/Cargo.toml.in

@@ -12,6 +12,7 @@ debug = true
 lua = []
 experimental = ["ntp-parser"]
 strict = []
+debug = []
 
 [dependencies]
 nom = "~3.2.1"

rust/Makefile.am

@@ -29,6 +29,10 @@ if HAVE_RUST_EXTERNAL
 RUST_FEATURES +=	experimental
 endif
 
+if DEBUG
+RUST_FEATURES +=	debug
+endif
+
 all-local:
 if HAVE_PYTHON
 	cd $(top_srcdir)/rust && \

rust/src/log.rs

@@ -114,6 +114,8 @@ macro_rules!SCLogConfig {
     }
 }
 
+// Debug mode: call C SCLogDebug
+#[cfg(feature = "debug")]
 #[macro_export]
 macro_rules!SCLogDebug {
     ($($arg:tt)*) => {
@@ -121,6 +123,15 @@ macro_rules!SCLogDebug {
     }
 }
 
+// Release mode: ignore arguments
+// Use a reference to avoid moving values.
+#[cfg(not(feature = "debug"))]
+#[macro_export]
+macro_rules!SCLogDebug {
+    ($last:expr) => { let _ = &$last; let _ = Level::Debug; };
+    ($one:expr, $($arg:tt)*) => { let _ = &$one; SCLogDebug!($($arg)*); };
+}
+
 #[no_mangle]
 pub extern "C" fn rs_log_set_level(level: i32) {
     unsafe {