cgen: fix address violations for return error(abc), reduce leaks in os

vlib/os/os.v

@@ -152,10 +152,11 @@ pub fn rmdir_all(path string) ? {
 	mut ret_err := ''
 	items := ls(path) ?
 	for item in items {
-		if is_dir(join_path(path, item)) {
-			rmdir_all(join_path(path, item))
+		fullpath := join_path(path, item)
+		if is_dir(fullpath) {
+			rmdir_all(fullpath)
 		}
-		rm(join_path(path, item)) or { ret_err = err }
+		rm(fullpath) or { ret_err = err }
 	}
 	rmdir(path) or { ret_err = err }
 	if ret_err.len > 0 {
@@ -402,13 +403,16 @@ pub fn is_abs_path(path string) bool {
 }
 
 // join_path returns a path as string from input string parameter(s).
+[manualfree]
 pub fn join_path(base string, dirs ...string) string {
 	mut result := []string{}
 	result << base.trim_right('\\/')
 	for d in dirs {
 		result << d
 	}
-	return result.join(path_separator)
+	res := result.join(path_separator)
+	unsafe { result.free() }
+	return res
 }
 
 // walk_ext returns a recursive list of all files in `path` ending with `ext`.
@@ -555,13 +559,20 @@ pub fn vmodules_paths() []string {
 // See https://discordapp.com/channels/592103645835821068/592294828432424960/630806741373943808
 // It gives a convenient way to access program resources like images, fonts, sounds and so on,
 // *no matter* how the program was started, and what is the current working directory.
+[manualfree]
 pub fn resource_abs_path(path string) string {
-	mut base_path := real_path(dir(executable()))
+	exe := executable()
+	dexe := dir(exe)
+	mut base_path := real_path(dexe)
 	vresource := getenv('V_RESOURCE_PATH')
 	if vresource.len != 0 {
 		base_path = vresource
 	}
-	return real_path(join_path(base_path, path))
+	fp := join_path(base_path, path)
+	res := real_path(fp)
+	fp.free()
+	base_path.free()
+	return res
 }
 
 pub struct Uname {

vlib/os/os_c.v

@@ -46,6 +46,7 @@ struct C.dirent {
 }
 
 // read_bytes returns all bytes read from file in `path`.
+[manualfree]
 pub fn read_bytes(path string) ?[]byte {
 	mut fp := vfopen(path, 'rb') ?
 	cseek := C.fseek(fp, 0, C.SEEK_END)
@@ -63,7 +64,9 @@ pub fn read_bytes(path string) ?[]byte {
 		return error('fread failed')
 	}
 	C.fclose(fp)
-	return res[0..nr_read_elements * fsize]
+	fres := res[0..nr_read_elements * fsize].clone()
+	unsafe { res.free() }
+	return fres
 }
 
 // read_file reads the file in `path` and returns the contents.
@@ -580,15 +583,18 @@ pub fn on_segfault(f voidptr) {
 
 // executable returns the path name of the executable that started the current
 // process.
+[manualfree]
 pub fn executable() string {
 	$if linux {
-		mut result := vcalloc(max_path_len)
-		count := C.readlink('/proc/self/exe', charptr(result), max_path_len)
+		mut xresult := vcalloc(max_path_len)
+		count := C.readlink('/proc/self/exe', charptr(xresult), max_path_len)
 		if count < 0 {
 			eprintln('os.executable() failed at reading /proc/self/exe to get exe path')
 			return executable_fallback()
 		}
-		return unsafe { result.vstring() }
+		res := unsafe { xresult.vstring() }.clone()
+		unsafe { free(xresult) }
+		return res
 	}
 	$if windows {
 		max := 512
@@ -713,15 +719,19 @@ pub fn getwd() string {
 		max := 512 // max_path_len * sizeof(wchar_t)
 		buf := &u16(vcalloc(max * 2))
 		if C._wgetcwd(buf, max) == 0 {
+			free(buf)
 			return ''
 		}
 		return string_from_wide(buf)
 	} $else {
 		buf := vcalloc(512)
 		if C.getcwd(charptr(buf), 512) == 0 {
+			free(buf)
 			return ''
 		}
-		return unsafe { buf.vstring() }
+		res := unsafe { buf.vstring() }.clone()
+		free(buf)
+		return res
 	}
 }
 
@@ -730,8 +740,12 @@ pub fn getwd() string {
 // Also https://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html
 // and https://insanecoding.blogspot.com/2007/11/implementing-realpath-in-c.html
 // NB: this particular rabbit hole is *deep* ...
+[manualfree]
 pub fn real_path(fpath string) string {
 	mut fullpath := vcalloc(max_path_len)
+	defer {
+		unsafe { free(fullpath) }
+	}
 	mut ret := charptr(0)
 	$if windows {
 		ret = charptr(C._fullpath(charptr(fullpath), charptr(fpath.str), max_path_len))
@@ -745,7 +759,9 @@ pub fn real_path(fpath string) string {
 		}
 	}
 	res := unsafe { fullpath.vstring() }
-	return normalize_drive_letter(res)
+	nres := normalize_drive_letter(res)
+	cres := nres.clone()
+	return cres
 }
 
 fn normalize_drive_letter(path string) string {

vlib/os/os_nix.c.v

@@ -90,10 +90,15 @@ pub fn ls(path string) ?[]string {
 		if isnil(ent) {
 			break
 		}
-		name := tos_clone(byteptr(ent.d_name))
-		if name != '.' && name != '..' && name != '' {
-			res << name
+		bptr := byteptr(ent.d_name)
+		unsafe {
+			if bptr[0] == 0 ||
+				(bptr[0] == `.` && bptr[1] == 0) ||
+				(bptr[0] == `.` && bptr[1] == `.` && bptr[2] == 0) {
+				continue
+			}
 		}
+		res << tos_clone(bptr)
 	}
 	C.closedir(dir)
 	return res

vlib/v/gen/cgen.v

@@ -4160,7 +4160,10 @@ fn (mut g Gen) return_statement(node ast.Return) {
 			g.expr_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)
 			g.writeln(';')
 			styp := g.typ(g.fn_decl.return_type)
-			g.writeln('return *($styp*)&$tmp;')
+			err_obj := g.new_tmp_var()
+			g.writeln('$styp $err_obj;')
+			g.writeln('memcpy(&$err_obj, &$tmp, sizeof(Option));')
+			g.writeln('return $err_obj;')
 			return
 		}
 	}