diff --git a/vlib/gg/gg.v b/vlib/gg/gg.v
index dbc4dff641..a371d4eecc 100644
--- a/vlib/gg/gg.v
+++ b/vlib/gg/gg.v
@@ -416,19 +416,23 @@ pub fn (ctx &GG) draw_line(x, y, x2, y2 f32, color gx.Color) {
 }
 
 pub fn (ctx &GG) draw_arc(x, y, r, start_angle, end_angle f32, segments int, color gx.Color) {
-	ctx.use_color_shader(color)
-	mut vertices := arc_vertices(x, y, r, start_angle, end_angle, segments)
+	ctx.use_color_shader(color)	
+	vertices := arc_vertices(x, y, r, start_angle, end_angle, segments)
 	ctx.bind_vertices(vertices)
 	gl.draw_arrays(C.GL_LINE_STRIP, 0, segments + 1)
+	unsafe { vertices.free() }
 }
 
 pub fn (ctx &GG) draw_filled_arc(x, y, r, start_angle, end_angle f32, segments int, color gx.Color) {
 	ctx.use_color_shader(color)
+
+	
 	mut vertices := []f32
-	vertices << [x, y]
+	vertices << [x, y] !
 	vertices << arc_vertices(x, y, r, start_angle, end_angle, segments)
 	ctx.bind_vertices(vertices)
 	gl.draw_arrays(C.GL_TRIANGLE_FAN, 0, segments + 2)
+	unsafe { vertices.free() }
 }
 
 pub fn (ctx &GG) draw_circle(x, y, r f32, color gx.Color) {
@@ -441,16 +445,17 @@ pub fn (ctx &GG) draw_rounded_rect(x, y, w, h, r f32, color gx.Color) {
 	segments := 6 + int(r / 8)
 
 	// Create a rounded rectangle using a triangle fan mesh.
-	vertices << [x + (w/2.0), y + (h/2.0)]
+	vertices << [x + (w/2.0), y + (h/2.0)] !
 	vertices << arc_vertices(x + w - r, y + h - r, r, 0, 90, segments)
 	vertices << arc_vertices(x + r, y + h - r, r, 90, 180, segments)
 	vertices << arc_vertices(x + r, y + r, r, 180, 270, segments)
 	vertices << arc_vertices(x + w - r, y + r, r, 270, 360, segments)
 	// Finish the loop by going back to the first vertex
-	vertices << [vertices[2], vertices[3]]
+	vertices << [vertices[2], vertices[3]] !
 
 	ctx.bind_vertices(vertices)
 	gl.draw_arrays(C.GL_TRIANGLE_FAN, 0, segments * 4 + 6)
+	unsafe { vertices.free() }
 }
 
 pub fn (ctx &GG) draw_empty_rounded_rect(x, y, w, h, r f32, color gx.Color) {
@@ -465,6 +470,7 @@ pub fn (ctx &GG) draw_empty_rounded_rect(x, y, w, h, r f32, color gx.Color) {
 
 	ctx.bind_vertices(vertices)
 	gl.draw_arrays(C.GL_LINE_STRIP, 0, segments * 4 + 1)
+	unsafe { vertices.free() }
 }
 
 /*
@@ -539,4 +545,4 @@ pub fn (c &GG) draw_empty_rect(x, y, w, h f32, color gx.Color) {
 
 pub fn scissor(x, y, w, h f32) {
 	C.glScissor(x, y, w, h)
-}
\ No newline at end of file
+}
diff --git a/vlib/gg/utils.v b/vlib/gg/utils.v
index 044d8d0030..0ae41096f2 100644
--- a/vlib/gg/utils.v
+++ b/vlib/gg/utils.v
@@ -11,14 +11,14 @@ fn arc_vertices(x, y, r, start_angle, end_angle f32, segments int) []f32 {
 	start_rads := start_angle * 0.0174533 // deg -> rad approx
 	end_rads := end_angle * 0.0174533
 	increment := (end_rads - start_rads) / segments
-	vertices << [x + f32(math.cos(start_rads)) * r, y + f32(math.sin(start_rads)) * r]
+	vertices << [x + f32(math.cos(start_rads)) * r, y + f32(math.sin(start_rads)) * r] !
 	mut i := 1
 	for i < segments {
 		theta := f32(i) * increment + start_rads
-		vertices << [x + f32(math.cos(theta)) * r, y + f32(math.sin(theta)) * r]
+		vertices << [x + f32(math.cos(theta)) * r, y + f32(math.sin(theta)) * r] !
 		i++
 	}
-	vertices << [x + f32(math.cos(end_rads)) * r, y + f32(math.sin(end_rads)) * r]
+	vertices << [x + f32(math.cos(end_rads)) * r, y + f32(math.sin(end_rads)) * r] !
 	return vertices
 }
 
diff --git a/vlib/os/os_nix.v b/vlib/os/os_nix.v
index 1171399b39..7d5b17399d 100644
--- a/vlib/os/os_nix.v
+++ b/vlib/os/os_nix.v
@@ -1,5 +1,7 @@
 module os
 
+import strings
+
 #include <dirent.h>
 #include <unistd.h>
 #include <fcntl.h>
@@ -198,18 +200,19 @@ pub fn exec(cmd string) ?Result {
 	if isnil(f) {
 		return error('exec("$cmd") failed')
 	}
-	buf := [1000]byte
-	mut res := ''
-	for C.fgets(charptr(buf), 1000, f) != 0 {
-		res += tos(buf, vstrlen(buf))
+	buf := [4096]byte
+	mut res := strings.new_builder(1024)
+	for C.fgets(charptr(buf), 4096, f) != 0 {
+		res.write_bytes( buf, vstrlen(buf) )
 	}
-	res = res.trim_space()
+	soutput := res.str().trim_space()
+	res.free()
 	exit_code := vpclose(f)
 	// if exit_code != 0 {
 	// return error(res)
 	// }
 	return Result{
-		output: res
+		output: soutput
 		exit_code: exit_code
 	}
 }
diff --git a/vlib/os/os_windows.v b/vlib/os/os_windows.v
index afc4bb1fc6..4ba30cf9d6 100644
--- a/vlib/os/os_windows.v
+++ b/vlib/os/os_windows.v
@@ -1,5 +1,7 @@
 module os
 
+import strings
+
 #flag -lws2_32
 #include <winsock2.h>
 
@@ -309,24 +311,25 @@ pub fn exec(cmd string) ?Result {
 	}
 	C.CloseHandle(child_stdin)
 	C.CloseHandle(child_stdout_write)
-	buf := [1000]byte
+	buf := [4096]byte
 	mut bytes_read := u32(0)
-	mut read_data := ''
+	mut read_data := strings.new_builder(1024)
 	for {
 		readfile_result := C.ReadFile(child_stdout_read, buf, 1000, voidptr(&bytes_read), 0)
-		read_data += tos(buf, int(bytes_read))
+		read_data.write_bytes(buf, int(bytes_read))
 		if readfile_result == false || int(bytes_read) == 0 {
 			break
 		}
 	}
-	read_data = read_data.trim_space()
+	soutput := read_data.str().trim_space()
+	read_data.free()
 	exit_code := u32(0)
 	C.WaitForSingleObject(proc_info.hProcess, C.INFINITE)
 	C.GetExitCodeProcess(proc_info.hProcess, voidptr(&exit_code))
 	C.CloseHandle(proc_info.hProcess)
 	C.CloseHandle(proc_info.hThread)
 	return Result {
-		output: read_data
+		output: soutput
 		exit_code: int(exit_code)
 	}
 }