v/checker: Warn about pointer indexing outside unsafe {} (#5918)

vlib/os/environment.v

@@ -76,8 +76,8 @@ pub fn environ() map[string]string {
 		C.FreeEnvironmentStringsW(estrings)
 	} $else {
 		e := &charptr(C.environ)
-		for i := 0; !isnil(e[i]); i++ {
-			eline := cstring_to_vstring(byteptr(e[i]))
+		for i := 0; !isnil(unsafe {e[i]}); i++ {
+			eline := unsafe {cstring_to_vstring(byteptr(e[i]))}
 			eq_index := eline.index_byte(`=`)
 			if eq_index > 0 {
 				res[eline[0..eq_index]] = eline[eq_index + 1..]

vlib/os/os.v

@@ -120,11 +120,12 @@ pub fn read_file(path string) ?string {
 	fsize := C.ftell(fp)
 	// C.fseek(fp, 0, SEEK_SET)  // same as `C.rewind(fp)` below
 	C.rewind(fp)
-	mut str := &byte(0)
-	unsafe { str = malloc(fsize + 1) }
-	C.fread(str, fsize, 1, fp)
-	str[fsize] = 0
-	return string(str,fsize)
+	unsafe {
+		mut str := malloc(fsize + 1)
+		C.fread(str, fsize, 1, fp)
+		str[fsize] = 0
+		return string(str,fsize)
+	}
 }
 
 /***************************** Utility  ops ************************/

vlib/os/os_nix.c.v

@@ -52,7 +52,7 @@ fn init_os_args(argc int, argv &&byte) []string {
 	// mut args := []string{len:argc}
 	for i in 0 .. argc {
 		// args [i] = string(argv[i])
-		args << string(argv[i])
+		args << unsafe {string(argv[i])}
 	}
 	return args
 }

vlib/os/os_windows.c.v

@@ -80,7 +80,7 @@ mut:
 fn init_os_args_wide(argc int, argv &byteptr) []string {
 	mut args := []string{}
 	for i in 0..argc {
-		args << string_from_wide(&u16(argv[i]))
+		args << string_from_wide(unsafe {&u16(argv[i])})
 	}
 	return args
 }