placeholder for C API logging, perhaps easiest to log through a representative logger instance

Makefile

@@ -100,6 +100,7 @@ DUKTAPE_SOURCES_SEPARATE =	\
 	$(DISTSRCSEP)/duk_api_thread.c \
 	$(DISTSRCSEP)/duk_api_buffer.c \
 	$(DISTSRCSEP)/duk_api_var.c \
+	$(DISTSRCSEP)/duk_api_logging.c \
 	$(DISTSRCSEP)/duk_api.c \
 	$(DISTSRCSEP)/duk_lexer.c \
 	$(DISTSRCSEP)/duk_js_call.c \

src/duk_api_logging.c

@@ -0,0 +1,41 @@
+/*
+ *  Logging
+ *
+ *  Current logging primitive is a sprintf-style log which is convenient
+ *  for most C code.  Another useful primitive would be to log N arguments
+ *  from value stack (like the Ecmascript binding does).
+ */
+
+#include "duk_internal.h"
+
+/* FIXME: dynamic? shared code with sprintf string pusher? */
+#define DUK__LOGFMT_BUFSIZE  256  /* size for formatting buffers */
+
+void duk_log(duk_context *ctx, int level, const char *fmt, ...) {
+	duk_hthread *thr = (duk_hthread *) ctx;
+	va_list ap;
+	char buf[DUK__LOGFMT_BUFSIZE];
+
+	va_start(ap, fmt);
+	DUK_VSNPRINTF(buf, sizeof(buf), fmt, ap);
+	buf[sizeof(buf) - 1] = (char) 0;
+	va_end(ap);
+
+	duk_push_hobject(ctx, thr->builtins[DUK_BIDX_LOGGER_CONSTRUCTOR]);
+	duk_get_prop_string(ctx, -1, "clog");  /*FIXME*/
+	duk_get_prop_string(ctx, -1, "info");  /*FIXME:level*/
+
+	/* [ ... Logger clog info ] */
+
+	duk_dup(ctx, -2);
+	duk_push_string(ctx, buf);  /*FIXME: duk_push_vsprintf? */
+
+	/* [ ... Logger clog info clog msg ] */
+
+	duk_call_method(ctx, 1 /*nargs*/);
+
+	/* [ ... Logger clog res ] */
+
+	duk_pop_3(ctx);
+}
+

src/duk_initjs.js

@@ -72,4 +72,9 @@
             }
         };
     }
+
+    // logger object for C code
+    if (true) {
+        D.Logger.clog = new D.Logger('C');
+    }
 })(this, Duktape);

util/make_dist.sh

@@ -70,6 +70,7 @@ for i in	\
 	duk_api_string.c	\
 	duk_api_thread.c	\
 	duk_api_var.c		\
+	duk_api_logging.c	\
 	duk_bi_array.c		\
 	duk_bi_boolean.c	\
 	duk_bi_buffer.c		\