diff --git a/0.3_roadmap.txt b/0.3_roadmap.txt
index dc8f159bda..1a4e4c01bb 100644
--- a/0.3_roadmap.txt
+++ b/0.3_roadmap.txt
@@ -6,11 +6,12 @@
 - thread safe arrays/maps
 - C2V translator
 - doom.v
-- rune type, replace ustring with []rune
+- rune type, replace `ustring` with `[]rune`, fix `byte.str()`
 - maps with non-string keys
 - iOS/Android support
 - make `-autofree` the default
 - parallel parser (and maybe checker/gen?)
+- `recover()` from panics
 
 
 
diff --git a/vlib/builtin/map.v b/vlib/builtin/map.v
index 3b65e4f4df..410c8dd861 100644
--- a/vlib/builtin/map.v
+++ b/vlib/builtin/map.v
@@ -4,7 +4,8 @@
 module builtin
 
 import strings
-import hash.wyhash
+//import hash.wyhash as hash
+import hash
 
 /*
 This is a highly optimized hashmap implementation. It has several traits that
@@ -225,7 +226,7 @@ fn new_map_init(n, value_bytes int, keys &string, values voidptr) map {
 
 [inline]
 fn (m &map) key_to_index(key string) (u32,u32) {
-	hash := wyhash.wyhash_c(key.str, u64(key.len), 0)
+	hash := hash.wyhash_c(key.str, u64(key.len), 0)
 	index := hash & m.cap
 	meta := ((hash >> m.shift) & hash_mask) | probe_inc
 	return u32(index),u32(meta)
diff --git a/vlib/hash/wyhash.v b/vlib/hash/wyhash.v
new file mode 100644
index 0000000000..4ca53e780f
--- /dev/null
+++ b/vlib/hash/wyhash.v
@@ -0,0 +1,139 @@
+// 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.
+//
+// this is an implementation of wyhash v4
+// from https://github.com/wangyi-fudan/wyhash
+//
+// TODO: use u128 once implemented
+// currently the C version performs slightly better
+// because it uses 128 bit int when available and
+// branch prediction hints. the C version will be
+// removed once the perfomance is matched.
+// you can test performance by running:
+// `v run cmd/tools/bench/wyhash.v`
+// try running with and without the `-prod` flag
+module hash
+
+//#flag -I @VROOT/thirdparty/wyhash
+//#include "wyhash.h"
+fn C.wyhash(byteptr, u64, u64) u64
+
+
+const (
+	wyp0 = u64(0xa0761d6478bd642f)
+	wyp1 = u64(0xe7037ed1a0b428db)
+	wyp2 = u64(0x8ebc6af09c88c6e3)
+	wyp3 = u64(0x589965cc75374cc3)
+	wyp4 = u64(0x1d8e4e27c47d124f)
+)
+
+[inline]
+pub fn wyhash_c(key byteptr, len, seed u64) u64 {
+	return C.wyhash(key, len, seed)
+}
+
+[inline]
+pub fn sum64_string(key string, seed u64) u64 {
+	return wyhash64(key.str, u64(key.len), seed)
+}
+
+[inline]
+pub fn sum64(key []byte, seed u64) u64 {
+	return wyhash64(byteptr(key.data), u64(key.len), seed)
+}
+
+[inline]
+fn wyhash64(key byteptr, len, seed_ u64) u64 {
+	if len == 0 {
+		return 0
+	}
+	mut p := key
+	mut seed := seed_
+	mut i := len & 63
+	unsafe {
+		if i < 4 {
+			seed = wymum(wyr3(p, i) ^ seed ^ wyp0, seed ^ wyp1)
+		}
+		else if i <= 8 {
+			seed = wymum(wyr4(p) ^ seed ^ wyp0, wyr4(p + i - 4) ^ seed ^ wyp1)
+		}
+		else if i <= 16 {
+			seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + i - 8) ^ seed ^ wyp1)
+		}
+		else if i <= 24 {
+			seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1) ^ wymum(wyr8(p + i - 8) ^ seed ^ wyp2, seed ^ wyp3)
+		}
+		else if i <= 32 {
+			seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1) ^ wymum(wyr8(p + 16) ^ seed ^ wyp2, wyr8(p + i - 8) ^ seed ^ wyp3)
+		}
+		else {
+			seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1) ^ wymum(wyr8(p + 16) ^ seed ^ wyp2, wyr8(p + 24) ^ seed ^ wyp3) ^ wymum(wyr8(p + i - 32) ^ seed ^ wyp1, wyr8(p + i - 24) ^ seed ^ wyp2) ^ wymum(wyr8(p + i - 16) ^ seed ^ wyp3, wyr8(p + i - 8) ^ seed ^ wyp0)
+		}
+	}
+	if i == len {
+		return wymum(seed, len ^ wyp4)
+	}
+	mut see1 := seed
+	mut see2 := seed
+	mut see3 := seed
+	unsafe {
+		p = p + i
+		for i = len - i; i >= 64; i -= 64 {
+			seed = wymum(wyr8(p) ^ seed ^ wyp0, wyr8(p + 8) ^ seed ^ wyp1)
+			see1 = wymum(wyr8(p + 16) ^ see1 ^ wyp2, wyr8(p + 24) ^ see1 ^ wyp3)
+			see2 = wymum(wyr8(p + 32) ^ see2 ^ wyp1, wyr8(p + 40) ^ see2 ^ wyp2)
+			see3 = wymum(wyr8(p + 48) ^ see3 ^ wyp3, wyr8(p + 56) ^ see3 ^ wyp0)
+			p = p + 64
+		}
+	}
+	return wymum(seed ^ see1 ^ see2, see3 ^ len ^ wyp4)
+}
+
+[inline]
+fn wyrotr(v u64, k u32) u64 {
+	return (v>>k) | (v<<(64 - k))
+}
+
+[inline]
+pub fn wymum(a, b u64) u64 {
+	/*
+	mut r := u128(a)
+	r = r*b
+	return (r>>64)^r
+	*/
+	mask32 := u32(4294967295)
+	x0 := a & mask32
+	x1 := a>>32
+	y0 := b & mask32
+	y1 := b>>32
+	w0 := x0 * y0
+	t := x1 * y0 + (w0>>32)
+	mut w1 := t & mask32
+	w2 := t>>32
+	w1 += x0 * y1
+	hi := x1 * y1 + w2 + (w1>>32)
+	lo := a * b
+	return hi ^ lo
+}
+
+[inline]
+fn wyr3(p byteptr, k u64) u64 {
+	unsafe {
+		return (u64(p[0])<<16) | (u64(p[k>>1])<<8) | u64(p[k - 1])
+	}
+}
+
+[inline]
+fn wyr4(p byteptr) u64 {
+	unsafe {
+		return u32(p[0]) | (u32(p[1])<<u32(8)) | (u32(p[2])<<u32(16)) | (u32(p[3])<<u32(24))
+	}
+}
+
+[inline]
+fn wyr8(p byteptr) u64 {
+	unsafe {
+		return u64(p[0]) | (u64(p[1])<<8) | (u64(p[2])<<16) | (u64(p[3])<<24) | (u64(p[4])<<32) | (u64(p[5])<<40) | (u64(p[6])<<48) | (u64(p[7])<<56)
+	}
+}
diff --git a/vlib/strconv/f32_str.v b/vlib/strconv/f32_str.v
index 8544eca452..2717c00b6e 100644
--- a/vlib/strconv/f32_str.v
+++ b/vlib/strconv/f32_str.v
@@ -65,7 +65,7 @@ const(
 
 // max 46 char
 // -3.40282346638528859811704183484516925440e+38
-fn (d Dec32) get_string_32(neg bool, i_n_digit int, i_pad_digit int) string {
+pub fn (d Dec32) get_string_32(neg bool, i_n_digit int, i_pad_digit int) string {
 	n_digit          := i_n_digit + 1
 	pad_digit        := i_pad_digit + 1
 	mut out          := d.m
diff --git a/vlib/v/builder/cc.v b/vlib/v/builder/cc.v
index c10ed6cd38..cb82fdbcd2 100644
--- a/vlib/v/builder/cc.v
+++ b/vlib/v/builder/cc.v
@@ -355,7 +355,7 @@ fn (mut v Builder) cc() {
 	}
 	if v.pref.use_cache {
 		// vexe := pref.vexe_path()
-		cached_modules := ['builtin', 'os', 'math', 'strconv', 'strings', 'hash.wyhash', 'strconv.ftoa']
+		cached_modules := ['builtin', 'os', 'math', 'strconv', 'strings', 'hash'] // , 'strconv.ftoa']
 		for cfile in cached_modules {
 			ofile := os.join_path(pref.default_module_path, 'cache', 'vlib', cfile.replace('.', '/') +
 				'.o')
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 5cc01ee769..3992970a90 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -102,7 +102,7 @@ mut:
 
 const (
 	tabs = ['', '\t', '\t\t', '\t\t\t', '\t\t\t\t', '\t\t\t\t\t', '\t\t\t\t\t\t', '\t\t\t\t\t\t\t',
-		'\t\t\t\t\t\t\t\t'
+		'\t\t\t\t\t\t\t\t',
 	]
 )
 
@@ -721,7 +721,7 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 			mut skip := false
 			pos := g.out.buf.len
 			if g.pref.build_mode == .build_module {
-				if !node.name.starts_with(g.module_built + '.') {
+				if !node.name.starts_with(g.module_built + '.') && node.mod != g.module_built {
 					// Skip functions that don't have to be generated
 					// for this module.
 					skip = true
@@ -743,7 +743,7 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 				node.name == 'backtrace_symbols_fd' {
 				g.write('\n#ifndef __cplusplus\n')
 			}
-			g.gen_fn_decl(node)
+			g.gen_fn_decl(node, skip)
 			if node.name == 'backtrace' ||
 				node.name == 'backtrace_symbols' ||
 				node.name == 'backtrace_symbols_fd' {
@@ -2376,7 +2376,7 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 			if !is_guard {
 				is_guard = true
 				guard_idx = i
-				guard_vars = []string{ len: node.branches.len }
+				guard_vars = []string{len: node.branches.len}
 				g.writeln('{ /* if guard */ ')
 			}
 			var_name := g.new_tmp_var()
@@ -2898,7 +2898,7 @@ fn (mut g Gen) go_back_out(n int) {
 
 const (
 	skip_struct_init = ['strconv__ftoa__Uf32', 'strconv__ftoa__Uf64', 'strconv__Float64u', 'struct stat',
-		'struct addrinfo'
+		'struct addrinfo',
 	]
 )
 
diff --git a/vlib/v/gen/fn.v b/vlib/v/gen/fn.v
index 358080c645..78809e66f6 100644
--- a/vlib/v/gen/fn.v
+++ b/vlib/v/gen/fn.v
@@ -7,7 +7,7 @@ import v.ast
 import v.table
 import v.util
 
-fn (mut g Gen) gen_fn_decl(it ast.FnDecl) {
+fn (mut g Gen) gen_fn_decl(it ast.FnDecl, skip bool) {
 	if it.language == .c {
 		// || it.no_body {
 		return
@@ -15,6 +15,9 @@ fn (mut g Gen) gen_fn_decl(it ast.FnDecl) {
 	// if g.fileis('vweb.v') {
 	// println('\ngen_fn_decl() $it.name $it.is_generic $g.cur_generic_type')
 	// }
+	if g.pref.use_cache && skip {
+		return
+	}
 	if it.is_generic && g.cur_generic_type == 0 { // need the cur_generic_type check to avoid inf. recursion
 		// loop thru each generic type and generate a function
 		for gen_type in g.table.fn_gen_types[it.name] {
@@ -23,7 +26,7 @@ fn (mut g Gen) gen_fn_decl(it ast.FnDecl) {
 				println('gen fn `$it.name` for type `$sym.name`')
 			}
 			g.cur_generic_type = gen_type
-			g.gen_fn_decl(it)
+			g.gen_fn_decl(it, skip)
 		}
 		g.cur_generic_type = 0
 		return
@@ -107,7 +110,7 @@ fn (mut g Gen) gen_fn_decl(it ast.FnDecl) {
 	fargs, fargtypes := g.fn_args(it.args, it.is_variadic)
 	if it.no_body || (g.pref.use_cache && it.is_builtin) {
 		// Just a function header. Builtin function bodies are defined in builtin.o
-		g.definitions.writeln(');')
+		g.definitions.writeln('); // NO BODY')
 		g.writeln(');')
 		return
 	}
diff --git a/vlib/v/util/util.v b/vlib/v/util/util.v
index 0e25c8ffa5..2c5aa8a3c9 100644
--- a/vlib/v/util/util.v
+++ b/vlib/v/util/util.v
@@ -12,7 +12,9 @@ pub const (
 
 // math.bits is needed by strconv.ftoa
 pub const (
-	builtin_module_parts = ['math.bits', 'strconv', 'strconv.ftoa', 'hash.wyhash', 'strings', 'builtin']
+	builtin_module_parts = ['math.bits', 'strconv', 'strconv.ftoa', 'hash', 'hash.wyhash', 'strings',
+		'builtin',
+	]
 )
 
 pub const (