Do not try to load the builtin driver if --driver=<file> has been used already.

Makefile

@@ -456,7 +456,8 @@ collect_copyrights:
 3rdparty/xmq/build/default/release/xmq: $(wildcard 3rdparty/xmq/src/main/c/* 3rdparty/xmq/src/main/c/parts/*)
 	@mkdir -p 3rdparty
 	@(cd 3rdparty; git clone --depth 1 https://github.com/libxmq/xmq.git; cd xmq; ./configure)
-	@if [ "$$(cat 3rdparty/xmq/build/default/spec.mk | grep CC)" = "CC:=gcc" ]; then (cd 3rdparty/xmq; make) ; else rm -f $@ ; mkdir -p $$(dirname $@); touch $@ ; echo "Could not build xmq." ; fi
+	@cat cat 3rdparty/xmq/build/default/spec.mk
+	@if [ "$$(cat 3rdparty/xmq/build/default/spec.mk | grep CC)" = "CC:=gcc" ]; then (cd 3rdparty/xmq; make VERBOSE=) ; else rm -f $@ ; mkdir -p $$(dirname $@); touch $@ ; echo "Could not build xmq." ; fi
 
 build/xmq: 3rdparty/xmq/build/default/release/xmq
 	@cp $< $@

src/drivers.cc

@@ -70,6 +70,12 @@ bool loadBuiltinDriver(string driver_name)
     // Check that there is such a builtin driver.
     if (builtins_name_lookup_.count(driver_name) == 0) return false;
 
+    if (lookupDriver(driver_name))
+    {
+        // A driver has already been loaded! Skip loading the builtin driver.
+        return true;
+    }
+
     BuiltinDriver *driver = builtins_name_lookup_[driver_name];
     if (driver->loaded) return true;
 

src/meters.h

@@ -231,6 +231,7 @@ public:
 
 bool registerDriver(function<void(DriverInfo&di)> setup);
 // Lookup (and load if necessary) driver from memory or disk.
+DriverInfo *lookupDriver(string name);
 bool lookupDriverInfo(const string& driver, DriverInfo *di = NULL);
 // Return the best driver match for a telegram.
 DriverInfo pickMeterDriver(Telegram *t);