Make duk_log() support artbirarily long log messages

Internally, use duk_push_vsprintf() for log message formatting, which now
has support for formatting 99% of messages with a stack buffer.

src/duk_api_logging.c

@@ -8,12 +8,8 @@
 
 #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, ...) {
 	va_list ap;
-	char buf[DUK__LOGFMT_BUFSIZE];
 	/* stridx_logfunc[] must be static to allow initializer with old compilers like BCC */
 	static const duk_uint16_t stridx_logfunc[6] = {
 		DUK_STRIDX_LC_TRACE, DUK_STRIDX_LC_DEBUG, DUK_STRIDX_LC_INFO,
@@ -26,21 +22,18 @@ void duk_log(duk_context *ctx, int level, const char *fmt, ...) {
 		level = (int) (sizeof(stridx_logfunc) / sizeof(duk_uint16_t)) - 1;
 	}
 
-	va_start(ap, fmt);
-	DUK_VSNPRINTF(buf, sizeof(buf), fmt, ap);
-	buf[sizeof(buf) - 1] = (char) 0;
-	va_end(ap);
-
 	duk_push_hobject_bidx(ctx, DUK_BIDX_LOGGER_CONSTRUCTOR);
 	duk_get_prop_stridx(ctx, -1, DUK_STRIDX_CLOG);
 	duk_get_prop_stridx(ctx, -1, stridx_logfunc[level]);
+	duk_dup(ctx, -2);
 
-	/* [ ... Logger clog info ] */
+	/* [ ... Logger clog logfunc clog ] */
 
-	duk_dup(ctx, -2);
-	duk_push_string(ctx, buf);  /* FIXME: duk_push_vsprintf? */
+	va_start(ap, fmt);
+	duk_push_vsprintf(ctx, fmt, ap);
+	va_end(ap);
 
-	/* [ ... Logger clog info clog msg ] */
+	/* [ ... Logger clog logfunc clog(=this) msg ] */
 
 	duk_call_method(ctx, 1 /*nargs*/);
 
@@ -48,4 +41,3 @@ void duk_log(duk_context *ctx, int level, const char *fmt, ...) {
 
 	duk_pop_3(ctx);
 }
-