diff --git a/vlib/builtin/array.v b/vlib/builtin/array.v
index 2925cb1fbb..3154dbda53 100644
--- a/vlib/builtin/array.v
+++ b/vlib/builtin/array.v
@@ -73,7 +73,9 @@ fn new_array_from_c_array(len, cap, elm_size int, c_array voidptr) array {
 		cap: cap_
 	}
 	// TODO Write all memory functions (like memcpy) in V
-	C.memcpy(arr.data, c_array, len * elm_size)
+	unsafe {
+		C.memcpy(arr.data, c_array, len * elm_size)
+	}
 	return arr
 }
 
@@ -125,7 +127,9 @@ pub fn (a array) repeat(count int) array {
 	for i in 0..count {
 		if a.len > 0 && a.element_size == sizeof(array) {
 			ary := array{}
-			C.memcpy(&ary, a.data, sizeof(array))
+			unsafe {
+				C.memcpy(&ary, a.data, sizeof(array))
+			}
 			ary_clone := ary.clone()
 			unsafe {
 				C.memcpy(arr.get_unsafe(i * a.len), &ary_clone, a.len * a.element_size)
@@ -516,7 +520,9 @@ pub fn copy(dst, src []byte) int {
 	if dst.len > 0 && src.len > 0 {
 		mut min := 0
 		min = if dst.len < src.len { dst.len } else { src.len }
-		C.memcpy(byteptr(dst.data), src[..min].data, dst.element_size * min)
+		unsafe {
+			C.memcpy(byteptr(dst.data), src[..min].data, dst.element_size * min)
+		}
 		return min
 	}
 	return 0
diff --git a/vlib/builtin/builtin.v b/vlib/builtin/builtin.v
index 81d24ac612..ece4bdc3c1 100644
--- a/vlib/builtin/builtin.v
+++ b/vlib/builtin/builtin.v
@@ -150,7 +150,7 @@ pub fn malloc(n int) byteptr {
 		nr_mallocs++
 		return res
 	} $else {
-		ptr := C.malloc(n)
+		ptr := unsafe {C.malloc(n)}
 		if ptr == 0 {
 			panic('malloc($n) failed')
 		}
@@ -177,12 +177,14 @@ TODO
 [unsafe_fn]
 pub fn v_realloc(b byteptr, n u32) byteptr {
 	$if prealloc {
-		new_ptr := malloc(int(n))
-		size := 0 //malloc_size(b)
-		C.memcpy(new_ptr, b, size)
-		return new_ptr
+		unsafe {
+			new_ptr := malloc(int(n))
+			size := 0 //malloc_size(b)
+			C.memcpy(new_ptr, b, size)
+			return new_ptr
+		}
 	} $else {
-		ptr := C.realloc(b, n)
+		ptr := unsafe {C.realloc(b, n)}
 		if ptr == 0 {
 			panic('realloc($n) failed')
 		}
@@ -217,8 +219,10 @@ pub fn memdup(src voidptr, sz int) voidptr {
 	if sz == 0 {
 		return vcalloc(1)
 	}
-	mem := malloc(sz)
-	return C.memcpy(mem, src, sz)
+	unsafe {
+		mem := malloc(sz)
+		return C.memcpy(mem, src, sz)
+	}
 }
 
 fn v_ptr_free(ptr voidptr) {
diff --git a/vlib/builtin/builtin_windows.c.v b/vlib/builtin/builtin_windows.c.v
index 9e48332134..0059603d9e 100644
--- a/vlib/builtin/builtin_windows.c.v
+++ b/vlib/builtin/builtin_windows.c.v
@@ -62,7 +62,9 @@ const (
 fn builtin_init() {
 	if is_atty(1) > 0 {
 		C.SetConsoleMode(C.GetStdHandle(C.STD_OUTPUT_HANDLE), C.ENABLE_PROCESSED_OUTPUT | 0x0004) // enable_virtual_terminal_processing
-		C.setbuf(C.stdout, 0)
+		unsafe {
+			C.setbuf(C.stdout, 0)
+		}
 	}
 	add_unhandled_exception_handler()
 }
diff --git a/vlib/builtin/cfns.c.v b/vlib/builtin/cfns.c.v
index 496c8dd0fa..da27376b52 100644
--- a/vlib/builtin/cfns.c.v
+++ b/vlib/builtin/cfns.c.v
@@ -125,7 +125,8 @@ fn C.mktime() int
 fn C.gettimeofday() int
 
 
-fn C.sleep() int
+[trusted_fn]
+fn C.sleep(int) int
 
 
 fn C.usleep() int
@@ -152,9 +153,11 @@ fn C.tolower() int
 fn C.toupper() int
 
 
+[trusted_fn]
 fn C.getchar() int
 
 
+[trusted_fn]
 fn C.strerror(int) charptr
 
 
diff --git a/vlib/builtin/map.v b/vlib/builtin/map.v
index 410c8dd861..c80b003d8f 100644
--- a/vlib/builtin/map.v
+++ b/vlib/builtin/map.v
@@ -88,7 +88,9 @@ fn fast_string_eq(a, b string) bool {
 	if a.len != b.len {
 		return false
 	}
-	return C.memcmp(a.str, b.str, b.len) == 0
+	unsafe {
+		return C.memcmp(a.str, b.str, b.len) == 0
+	}
 }
 
 // Dynamic array with very low growth factor
@@ -502,11 +504,13 @@ pub fn (d DenseArray) clone() DenseArray {
 		cap:         d.cap
 		len:        d.len
 		deletes:     d.deletes
-		keys:        &string(malloc(int(d.cap * sizeof(string))))
-		values:      byteptr(malloc(int(d.cap * u32(d.value_bytes))))
+		keys:        unsafe {&string(malloc(int(d.cap * sizeof(string))))}
+		values:      unsafe {byteptr(malloc(int(d.cap * u32(d.value_bytes))))}
+	}
+	unsafe {
+		C.memcpy(res.keys, d.keys, d.cap * sizeof(string))
+		C.memcpy(res.values, d.values, d.cap * u32(d.value_bytes))
 	}
-	C.memcpy(res.keys, d.keys, d.cap * sizeof(string))
-	C.memcpy(res.values, d.values, d.cap * u32(d.value_bytes))
 	return res
 }
 
diff --git a/vlib/builtin/option.v b/vlib/builtin/option.v
index 7f698487c6..3c33c850d3 100644
--- a/vlib/builtin/option.v
+++ b/vlib/builtin/option.v
@@ -73,7 +73,9 @@ fn opt_ok(data voidptr, size int) Option {
 	res := Option{
 		ok: true
 	}
-	C.memcpy(res.data, data, size)
+	unsafe {
+		C.memcpy(res.data, data, size)
+	}
 	return res
 }
 
diff --git a/vlib/builtin/sorted_map.v b/vlib/builtin/sorted_map.v
index 0a00b9388f..3a99fe5f11 100644
--- a/vlib/builtin/sorted_map.v
+++ b/vlib/builtin/sorted_map.v
@@ -79,7 +79,9 @@ fn (mut m SortedMap) set(key string, value voidptr) {
 			}
 			parent.split_child(child_index, mut node)
 			if key == parent.keys[child_index] {
-				C.memcpy(parent.values[child_index], value, m.value_bytes)
+				unsafe {
+					C.memcpy(parent.values[child_index], value, m.value_bytes)
+				}
 				return
 			}
 			node = if key < parent.keys[child_index] {
@@ -91,7 +93,9 @@ fn (mut m SortedMap) set(key string, value voidptr) {
 		mut i := 0
 		for i < node.len && key > node.keys[i] { i++ }
 		if i != node.len && key == node.keys[i] {
-			C.memcpy(node.values[i], value, m.value_bytes)
+			unsafe {
+				C.memcpy(node.values[i], value, m.value_bytes)
+			}
 			return
 		}
 		if isnil(node.children) {
@@ -103,7 +107,9 @@ fn (mut m SortedMap) set(key string, value voidptr) {
 			}
 			node.keys[j + 1] = key
 			node.values[j + 1] = malloc(m.value_bytes)
-			C.memcpy(node.values[j + 1], value, m.value_bytes)
+			unsafe {
+				C.memcpy(node.values[j + 1], value, m.value_bytes)
+			}
 			node.len++
 			m.len++
 			return
@@ -150,7 +156,9 @@ fn (m SortedMap) get(key string, out voidptr) bool {
 		mut i := node.len - 1
 		for i >= 0 && key < node.keys[i] { i-- }
 		if i != -1 && key == node.keys[i] {
-			C.memcpy(out, node.values[i], m.value_bytes)
+			unsafe {
+				C.memcpy(out, node.values[i], m.value_bytes)
+			}
 			return true
 		}
 		if isnil(node.children) {
diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index b87f04f11e..2b5d987248 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -66,8 +66,9 @@ pub mut:
 	len   int
 }
 
+[unsafe_fn]
 pub fn vstrlen(s byteptr) int {
-	return C.strlen(charptr(s))
+	return unsafe {C.strlen(charptr(s))}
 }
 
 // Converts a C string to a V string.
@@ -107,14 +108,14 @@ pub fn tos3(s charptr) string {
 	}
 	return string{
 		str: byteptr(s)
-		len: C.strlen(s)
+		len: unsafe {C.strlen(s)}
 	}
 }
 
 pub fn tos_lit(s charptr) string {
 	return string{
 		str: byteptr(s)
-		len: C.strlen(s)
+		len: unsafe {C.strlen(s)}
 		is_lit: 1
 	}
 }
@@ -371,7 +372,9 @@ fn (s string) eq(a string) bool {
 	if s.len != a.len {
 		return false
 	}
-	return C.memcmp(s.str, a.str, a.len) == 0
+	unsafe {
+		return C.memcmp(s.str, a.str, a.len) == 0
+	}
 }
 
 // !=
@@ -1379,7 +1382,9 @@ pub fn (s string) bytes() []byte {
 		return []
 	}
 	mut buf := []byte{ len:s.len }
-	C.memcpy(buf.data, s.str, s.len)
+	unsafe {
+		C.memcpy(buf.data, s.str, s.len)
+	}
 	return buf
 }
 
diff --git a/vlib/os/environment.v b/vlib/os/environment.v
index ea93c657f4..f2ec075921 100644
--- a/vlib/os/environment.v
+++ b/vlib/os/environment.v
@@ -32,11 +32,15 @@ pub fn setenv(name string, value string, overwrite bool) int {
 	$if windows {
 		format := '$name=$value'
 		if overwrite {
-			return C._putenv(format.str)
+			unsafe {
+				return C._putenv(format.str)
+			}
 		}
 		return -1
 	} $else {
-		return C.setenv(charptr(name.str), charptr(value.str), overwrite)
+		unsafe {
+			return C.setenv(charptr(name.str), charptr(value.str), overwrite)
+		}
 	}
 }
 
diff --git a/vlib/os/inode.v b/vlib/os/inode.v
index 7d407a488a..4145ff8a2b 100644
--- a/vlib/os/inode.v
+++ b/vlib/os/inode.v
@@ -32,7 +32,9 @@ pub:
 // it supports windows for regular files but it doesn't matter if you use owner, group or others when checking permissions on windows
 pub fn inode(path string) FileMode {
 	mut attr := C.stat{}
-	C.stat(charptr(path.str), &attr)
+	unsafe {
+		C.stat(charptr(path.str), &attr)
+	}
 
 	mut typ := FileType.regular
 	if attr.st_mode & u32(C.S_IFMT) == u32(C.S_IFDIR) {
diff --git a/vlib/os/os.v b/vlib/os/os.v
index 83ccc3e237..d9f0e442e6 100644
--- a/vlib/os/os.v
+++ b/vlib/os/os.v
@@ -140,14 +140,16 @@ pub fn (mut f File) flush() {
 // file_size returns the size of the file located in `path`.
 pub fn file_size(path string) int {
 	mut s := C.stat{}
-	$if windows {
-		$if tinyc {
-			C.stat(charptr(path.str), voidptr(&s))
+	unsafe {
+		$if windows {
+			$if tinyc {
+				C.stat(charptr(path.str), &s)
+			} $else {
+				C._wstat(path.to_wide(), voidptr(&s))
+			}
 		} $else {
-			C._wstat(path.to_wide(), voidptr(&s))
+			C.stat(charptr(path.str), &s)
 		}
-	} $else {
-		C.stat(charptr(path.str), voidptr(&s))
 	}
 	return s.st_size
 }
@@ -193,7 +195,9 @@ pub fn cp(old, new string) ? {
 			}
 		}
 		from_attr := C.stat{}
-		C.stat(charptr(old.str), &from_attr)
+		unsafe {
+			C.stat(charptr(old.str), &from_attr)
+		}
 		if C.chmod(charptr(new.str), from_attr.st_mode) < 0 {
 			return error_with_code('failed to set permissions for $new', int(-1))
 		}
@@ -444,9 +448,13 @@ pub fn system(cmd string) int {
 	$if windows {
 		// overcome bug in system & _wsystem (cmd) when first char is quote `"`
 		wcmd := if cmd.len > 1 && cmd[0] == `"` && cmd[1] != `"` { '"$cmd"' } else { cmd }
-		ret = C._wsystem(wcmd.to_wide())
+		unsafe {
+			ret = C._wsystem(wcmd.to_wide())
+		}
 	} $else {
-		ret = C.system(charptr(cmd.str))
+		unsafe {
+			ret = C.system(charptr(cmd.str))
+		}
 	}
 	if ret == -1 {
 		print_c_errno()
@@ -1095,7 +1103,7 @@ pub fn is_dir(path string) bool {
 		return false
 	} $else {
 		statbuf := C.stat{}
-		if C.stat(charptr(path.str), &statbuf) != 0 {
+		if unsafe {C.stat(charptr(path.str), &statbuf)} != 0 {
 			return false
 		}
 		// ref: https://code.woboq.org/gcc/include/sys/stat.h.html
@@ -1231,8 +1239,11 @@ pub fn walk(path string, f fn(path string)) {
 	return
 }
 
+[unsafe_fn]
 pub fn signal(signum int, handler voidptr) {
-	C.signal(signum, handler)
+	unsafe {
+		C.signal(signum, handler)
+	}
 }
 
 pub fn fork() int {
@@ -1260,7 +1271,9 @@ pub fn wait() int {
 pub fn file_last_mod_unix(path string) int {
 	attr := C.stat{}
 	// # struct stat attr;
-	C.stat(charptr(path.str), &attr)
+	unsafe {
+		C.stat(charptr(path.str), &attr)
+	}
 	// # stat(path.str, &attr);
 	return attr.st_mtime
 	// # return attr.st_mtime ;
diff --git a/vlib/os/os_nix.c.v b/vlib/os/os_nix.c.v
index 795887b844..39a8aa4455 100644
--- a/vlib/os/os_nix.c.v
+++ b/vlib/os/os_nix.c.v
@@ -121,7 +121,7 @@ pub fn mkdir(path string) ?bool {
 		}
 	}
   */
-	r := C.mkdir(charptr(apath.str), 511)
+	r := unsafe {C.mkdir(charptr(apath.str), 511)}
 	if r == -1 {
 		return error(posix_get_error_msg(C.errno))
 	}
diff --git a/vlib/time/parse.v b/vlib/time/parse.v
index 7127df88b1..1b48f3cca0 100644
--- a/vlib/time/parse.v
+++ b/vlib/time/parse.v
@@ -42,8 +42,8 @@ pub fn parse_rfc2822(s string) ?Time {
 	mm := pos / 3 + 1
 	mut tmstr := byteptr(0)
 	unsafe { tmstr = malloc(s.len * 2) }
-	count := C.snprintf(charptr(tmstr), (s.len *  2), '%s-%02d-%s %s', fields[3].str, mm,
-		fields[1].str, fields[4].str)
+	count := unsafe {C.snprintf(charptr(tmstr), (s.len * 2), '%s-%02d-%s %s', fields[3].str, mm,
+		fields[1].str, fields[4].str)}
 
 	return parse(tos(tmstr, count))
 }
@@ -67,10 +67,10 @@ pub fn parse_iso8601(s string) ?Time {
 	mut offset_hour := 0
 	mut offset_min  := 0
 
-	count := C.sscanf(charptr(s.str), "%4d-%2d-%2d%c%2d:%2d:%2d.%6d%c%2d:%2d", &year, &month, &day,
+	count := unsafe {C.sscanf(charptr(s.str), "%4d-%2d-%2d%c%2d:%2d:%2d.%6d%c%2d:%2d", &year, &month, &day,
 													  &time_char, &hour, &minute,
 													  &second, &mic_second, &plus_min,
-													  &offset_hour, &offset_min)
+													  &offset_hour, &offset_min)}
 
 	if count != 11 {
 		return error('Invalid 8601 format')
diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index 77a1207611..3866ecd901 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -1096,12 +1096,16 @@ pub fn (stmt Stmt) position() token.Position {
 // field table.Field.default_expr, which should be ast.Expr
 pub fn fe2ex(x table.FExpr) Expr {
 	res := Expr{}
-	C.memcpy(&res, &x, sizeof(Expr))
+	unsafe {
+		C.memcpy(&res, &x, sizeof(Expr))
+	}
 	return res
 }
 
 pub fn ex2fe(x Expr) table.FExpr {
 	res := table.FExpr{}
-	C.memcpy(&res, &x, sizeof(table.FExpr))
+	unsafe {
+		C.memcpy(&res, &x, sizeof(table.FExpr))
+	}
 	return res
 }
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 781d9a84b3..eb9ec0197f 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1128,6 +1128,12 @@ pub fn (mut c Checker) call_fn(mut call_expr ast.CallExpr) table.Type {
 	if f.is_deprecated {
 		c.warn('function `$f.name` has been deprecated', call_expr.pos)
 	}
+	if f.is_unsafe && !c.inside_unsafe &&
+		f.language == .c && f.name[2] in [`m`, `s`] && f.mod == 'builtin' {
+		// builtin C.m*, C.s* only - temp
+		c.warn('function `$f.name` must be called from an `unsafe` block',
+			call_expr.pos)
+	}
 	if f.is_generic && f.return_type.has_flag(.generic) {
 		rts := c.table.get_type_symbol(f.return_type)
 		if rts.kind == .struct_ {
diff --git a/vlib/v/checker/tests/pointer_arithmetic_should_be_checked.out b/vlib/v/checker/tests/pointer_arithmetic_should_be_checked.out
deleted file mode 100644
index ab7d9c8fe0..0000000000
--- a/vlib/v/checker/tests/pointer_arithmetic_should_be_checked.out
+++ /dev/null
@@ -1,34 +0,0 @@
-vlib/v/checker/tests/pointer_arithmetic_should_be_checked.v:4:6: error: pointer arithmetic is only allowed in `unsafe` blocks
-    2 |     v := 5
-    3 |     mut p := &v
-    4 |     p++
-      |      ~~
-    5 |     p += 2
-    6 |     _ := v
-vlib/v/checker/tests/pointer_arithmetic_should_be_checked.v:5:7: error: pointer arithmetic is only allowed in `unsafe` blocks
-    3 |     mut p := &v
-    4 |     p++
-    5 |     p += 2
-      |       ~~
-    6 |     _ := v
-    7 | }
-vlib/v/checker/tests/pointer_arithmetic_should_be_checked.v:11:14: error: pointer arithmetic is only allowed in `unsafe` blocks
-    9 | fn test_ptr_infix() {
-   10 |     v := 4
-   11 |     mut q := &v - 1
-      |              ^
-   12 |     q = q + 3
-   13 |     _ := q
-vlib/v/checker/tests/pointer_arithmetic_should_be_checked.v:12:9: error: pointer arithmetic is only allowed in `unsafe` blocks
-   10 |     v := 4
-   11 |     mut q := &v - 1
-   12 |     q = q + 3
-      |         ^
-   13 |     _ := q
-   14 |     _ := v
-vlib/v/checker/tests/pointer_arithmetic_should_be_checked.v:24:7: error: method `S1.f` must be called from an `unsafe` block
-   22 | fn test_funcs() {
-   23 |     s := S1{}
-   24 |     s.f()
-      |       ~~~
-   25 | }
diff --git a/vlib/v/checker/tests/unsafe_c_calls_should_be_checked.out b/vlib/v/checker/tests/unsafe_c_calls_should_be_checked.out
new file mode 100644
index 0000000000..6a2e7aa013
--- /dev/null
+++ b/vlib/v/checker/tests/unsafe_c_calls_should_be_checked.out
@@ -0,0 +1,13 @@
+vlib/v/checker/tests/unsafe_c_calls_should_be_checked.v:3:16: error: function `C.malloc` must be called from an `unsafe` block
+    1 |
+    2 | fn test_c() {
+    3 |     mut p := C.malloc(4)
+      |                ~~~~~~~~~
+    4 |     s := 'hope'
+    5 |     C.memcpy(p, s.str, 4)
+vlib/v/checker/tests/unsafe_c_calls_should_be_checked.v:5:7: error: function `C.memcpy` must be called from an `unsafe` block
+    3 |     mut p := C.malloc(4)
+    4 |     s := 'hope'
+    5 |     C.memcpy(p, s.str, 4)
+      |       ~~~~~~~~~~~~~~~~~~~
+    6 | }
diff --git a/vlib/v/checker/tests/unsafe_c_calls_should_be_checked.vv b/vlib/v/checker/tests/unsafe_c_calls_should_be_checked.vv
new file mode 100644
index 0000000000..092fe2c1b0
--- /dev/null
+++ b/vlib/v/checker/tests/unsafe_c_calls_should_be_checked.vv
@@ -0,0 +1,6 @@
+
+fn test_c() {
+    mut p := C.malloc(4)
+    s := 'hope'
+    C.memcpy(p, s.str, 4)
+}
diff --git a/vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.out b/vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.out
new file mode 100644
index 0000000000..05aef5b1fb
--- /dev/null
+++ b/vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.out
@@ -0,0 +1,34 @@
+vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.v:4:6: error: pointer arithmetic is only allowed in `unsafe` blocks
+    2 |     v := 5
+    3 |     mut p := &v
+    4 |     p++
+      |      ~~
+    5 |     p += 2
+    6 |     _ := v
+vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.v:5:7: error: pointer arithmetic is only allowed in `unsafe` blocks
+    3 |     mut p := &v
+    4 |     p++
+    5 |     p += 2
+      |       ~~
+    6 |     _ := v
+    7 | }
+vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.v:11:14: error: pointer arithmetic is only allowed in `unsafe` blocks
+    9 | fn test_ptr_infix() {
+   10 |     v := 4
+   11 |     mut q := &v - 1
+      |              ^
+   12 |     q = q + 3
+   13 |     _ := q
+vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.v:12:9: error: pointer arithmetic is only allowed in `unsafe` blocks
+   10 |     v := 4
+   11 |     mut q := &v - 1
+   12 |     q = q + 3
+      |         ^
+   13 |     _ := q
+   14 |     _ := v
+vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.v:24:7: error: method `S1.f` must be called from an `unsafe` block
+   22 | fn test_funcs() {
+   23 |     s := S1{}
+   24 |     s.f()
+      |       ~~~
+   25 | }
diff --git a/vlib/v/checker/tests/pointer_arithmetic_should_be_checked.vv b/vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.vv
similarity index 100%
rename from vlib/v/checker/tests/pointer_arithmetic_should_be_checked.vv
rename to vlib/v/checker/tests/unsafe_pointer_arithmetic_should_be_checked.vv
diff --git a/vlib/v/gen/x64/gen.v b/vlib/v/gen/x64/gen.v
index 0e28211ba0..b428e7402a 100644
--- a/vlib/v/gen/x64/gen.v
+++ b/vlib/v/gen/x64/gen.v
@@ -620,7 +620,7 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 				if word.len != 2 {
 					verror('opcodes format: xx xx xx xx')
 				}
-				b := C.strtol(charptr(word.str), 0, 16)
+				b := unsafe {C.strtol(charptr(word.str), 0, 16)}
 				// b := word.byte()
 				// println('"$word" $b')
 				g.write8(b)
diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index 6523afebfa..0c63dab250 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -132,7 +132,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	p.top_level_statement_start()
 	start_pos := p.tok.position()
 	is_deprecated := 'deprecated' in p.attrs
-	is_unsafe := 'unsafe_fn' in p.attrs
+	mut is_unsafe := 'unsafe_fn' in p.attrs
 	is_pub := p.tok.kind == .key_pub
 	if is_pub {
 		p.next()
@@ -141,6 +141,7 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 	p.open_scope()
 	// C. || JS.
 	language := if p.tok.kind == .name && p.tok.lit == 'C' {
+		is_unsafe = !('trusted_fn' in p.attrs)
 		table.Language.c
 	} else if p.tok.kind == .name && p.tok.lit == 'JS' {
 		table.Language.js
diff --git a/vlib/v/util/util.v b/vlib/v/util/util.v
index 8f6dc947e2..e7ead5268f 100644
--- a/vlib/v/util/util.v
+++ b/vlib/v/util/util.v
@@ -27,7 +27,9 @@ pub const (
 pub fn vhash() string {
 	mut buf := [50]byte
 	buf[0] = 0
-	C.snprintf(charptr(buf), 50, '%s', C.V_COMMIT_HASH)
+	unsafe {
+		C.snprintf(charptr(buf), 50, '%s', C.V_COMMIT_HASH)
+	}
 	return tos_clone(buf)
 }
 
@@ -97,7 +99,9 @@ pub fn githash(should_get_from_filesystem bool) string {
 	}
 	mut buf := [50]byte
 	buf[0] = 0
-	C.snprintf(charptr(buf), 50, '%s', C.V_CURRENT_COMMIT_HASH)
+	unsafe {
+		C.snprintf(charptr(buf), 50, '%s', C.V_CURRENT_COMMIT_HASH)
+	}
 	return tos_clone(buf)
 }