diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index ed5391400e..1ad4e29b1b 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -2172,109 +2172,6 @@ fn (mut g Gen) write_init_function() {
 	}
 }
 
-fn (mut g Gen) write_str_fn_definitions() {
-	// _STR function can't be defined in vlib
-	g.writeln('
-void _STR_PRINT_ARG(const char *fmt, char** refbufp, int *nbytes, int *memsize, int guess, ...) {
-	va_list args;
-	va_start(args, guess);
-	for(;;) {
-		if (guess < *memsize - *nbytes) {
-			guess = vsnprintf(*refbufp + *nbytes, *memsize - *nbytes, fmt, args);
-			if (guess < *memsize - *nbytes) { // result did fit into buffer
-				*nbytes += guess;
-				return;
-			}
-		}
-		// increase buffer (somewhat exponentially)
-		*memsize += (*memsize + *memsize) / 3 + guess;
-		*refbufp = realloc(*refbufp, *memsize);
-	}
-}
-
-string _STR(const char *fmt, int nfmts, ...) {
-	va_list argptr;
-	int memsize = 128;
-	int nbytes = 0;
-	char* buf = malloc(memsize);
-	va_start(argptr, nfmts);
-	for (int i=0; i<nfmts; i++) {
-		int k = strlen(fmt);
-		bool is_fspec = false;
-		for (int j=0; j<k; j++) {
-			if (fmt[j] == ' +
-		"'%'" + ') {
-				j++;
-				if(fmt[j] != ' + "'%'" + ') {
-					is_fspec = true;
-					break;
-				}
-			}
-		}
-		if (is_fspec) {
-			char f = fmt[k-1];
-			char fup = f & 0xdf; // toupper
-			bool l = fmt[k-2] == ' +
-		"'l'" + ';
-			bool ll = l && fmt[k-3] == ' + "'l'" + ';
-			if (f == ' + "'u'" + ' || fup == ' +
-		"'X'" + ' || f == ' + "'o'" + ' || f == ' + "'d'" + ' || f == ' + "'c'" + ') { // int...
-				if (ll) _STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+16, va_arg(argptr, long long));
-				else if (l) _STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+10, va_arg(argptr, long));
-				else _STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+8, va_arg(argptr, int));
-			} else if (fup >= ' +
-		"'E'" + ' && fup <= ' + "'G'" + ') { // floating point
-				_STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+10, va_arg(argptr, double));
-			} else if (f == ' +
-		"'s'" + ') { // v string
-				string s = va_arg(argptr, string);
-				if (fmt[k-4] == ' + "'*'" +
-		') { // %*.*s
-					int fwidth = va_arg(argptr, int);
-					if (fwidth < 0)
-						fwidth -= (s.len - utf8_str_len(s));
-					else
-						fwidth += (s.len - utf8_str_len(s));
-					_STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+fwidth-4, fwidth, s.len, s.str);
-				} else { // %.*s
-					_STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+s.len-4, s.len, s.str);
-				}
-			} else {
-				v_panic(tos3("Invaid format specifier"));
-			}
-		} else {
-			if (k)
-				_STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k);
-		}
-		fmt += k+1;
-	}
-	va_end(argptr);
-	buf[nbytes] = 0;
-	buf = realloc(buf, nbytes+1);
-#ifdef DEBUG_ALLOC
-	puts("_STR:");
-	puts(buf);
-#endif
-	return tos2(buf);
-}
-
-string _STR_TMP(const char *fmt, ...) {
-	va_list argptr;
-	va_start(argptr, fmt);
-	//size_t len = vsnprintf(0, 0, fmt, argptr) + 1;
-	va_end(argptr);
-	va_start(argptr, fmt);
-	vsprintf((char *)g_str_buf, fmt, argptr);
-	va_end(argptr);
-#ifdef DEBUG_ALLOC
-	//puts("_STR_TMP:");
-	//puts(g_str_buf);
-#endif
-	return tos2(g_str_buf);
-} // endof _STR_TMP
-
-')
-}
 
 const (
 	builtins = ['string', 'array', 'KeyValue', 'DenseArray', 'map', 'Option']
diff --git a/vlib/v/gen/str.v b/vlib/v/gen/str.v
new file mode 100644
index 0000000000..9e7a5d662a
--- /dev/null
+++ b/vlib/v/gen/str.v
@@ -0,0 +1,102 @@
+// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module gen
+
+fn (mut g Gen) write_str_fn_definitions() {
+	// _STR function can't be defined in vlib
+	g.writeln("
+void _STR_PRINT_ARG(const char *fmt, char** refbufp, int *nbytes, int *memsize, int guess, ...) {
+	va_list args;
+	va_start(args, guess);
+	for(;;) {
+		if (guess < *memsize - *nbytes) {
+			guess = vsnprintf(*refbufp + *nbytes, *memsize - *nbytes, fmt, args);
+			if (guess < *memsize - *nbytes) { // result did fit into buffer
+				*nbytes += guess;
+				return;
+			}
+		}
+		// increase buffer (somewhat exponentially)
+		*memsize += (*memsize + *memsize) / 3 + guess;
+		*refbufp = realloc(*refbufp, *memsize);
+	}
+}
+
+string _STR(const char *fmt, int nfmts, ...) {
+	va_list argptr;
+	int memsize = 128;
+	int nbytes = 0;
+	char* buf = malloc(memsize);
+	va_start(argptr, nfmts);
+	for (int i=0; i<nfmts; i++) {
+		int k = strlen(fmt);
+		bool is_fspec = false;
+		for (int j=0; j<k; j++) {
+			if (fmt[j] == '%') {
+				j++;
+				if (fmt[j] != '%') {
+					is_fspec = true;
+					break;
+				}
+			}
+		}
+		if (is_fspec) {
+			char f = fmt[k-1];
+			char fup = f & 0xdf; // toupper
+			bool l = fmt[k-2] == 'l';
+			bool ll = l && fmt[k-3] == 'l';
+			if (f == 'u' || fup == 'X' || f == 'o' || f == 'd' || f == 'c') { // int...
+				if (ll) _STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+16, va_arg(argptr, long long));
+				else if (l) _STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+10, va_arg(argptr, long));
+				else _STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+8, va_arg(argptr, int));
+			} else if (fup >= 'E' && fup <= 'G') { // floating point
+				_STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+10, va_arg(argptr, double));
+			} else if (f == 's') { // v string
+				string s = va_arg(argptr, string);
+				if (fmt[k-4] == '*') { // %*.*s
+					int fwidth = va_arg(argptr, int);
+					if (fwidth < 0)
+						fwidth -= (s.len - utf8_str_len(s));
+					else
+						fwidth += (s.len - utf8_str_len(s));
+					_STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+fwidth-4, fwidth, s.len, s.str);
+				} else { // %.*s
+					_STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k+s.len-4, s.len, s.str);
+				}
+			} else {
+				//v_panic(tos3('Invaid format specifier'));
+			}
+		} else {
+			if (k)
+				_STR_PRINT_ARG(fmt, &buf, &nbytes, &memsize, k);
+		}
+		fmt += k+1;
+	}
+	va_end(argptr);
+	buf[nbytes] = 0;
+	buf = realloc(buf, nbytes+1);
+#ifdef DEBUG_ALLOC
+	//puts('_STR:');
+	puts(buf);
+#endif
+	return tos2(buf);
+}
+
+string _STR_TMP(const char *fmt, ...) {
+	va_list argptr;
+	va_start(argptr, fmt);
+	//size_t len = vsnprintf(0, 0, fmt, argptr) + 1;
+	va_end(argptr);
+	va_start(argptr, fmt);
+	vsprintf((char *)g_str_buf, fmt, argptr);
+	va_end(argptr);
+#ifdef DEBUG_ALLOC
+	//puts('_STR_TMP:');
+	//puts(g_str_buf);
+#endif
+	return tos2(g_str_buf);
+} // endof _STR_TMP
+
+")
+}