checker: check unsafe V function calls (#8752)

vlib/os/environment.c.v

@@ -12,19 +12,21 @@ fn C.FreeEnvironmentStringsW(&u16) int
 
 // `getenv` returns the value of the environment variable named by the key.
 pub fn getenv(key string) string {
-	$if windows {
-		s := C._wgetenv(key.to_wide())
-		if s == 0 {
-			return ''
+	unsafe {
+		$if windows {
+			s := C._wgetenv(key.to_wide())
+			if s == 0 {
+				return ''
+			}
+			return string_from_wide(s)
+		} $else {
+			s := C.getenv(charptr(key.str))
+			if s == voidptr(0) {
+				return ''
+			}
+			// NB: C.getenv *requires* that the result be copied.
+			return cstring_to_vstring(byteptr(s))
 		}
-		return string_from_wide(s)
-	} $else {
-		s := C.getenv(charptr(key.str))
-		if s == voidptr(0) {
-			return ''
-		}
-		// NB: C.getenv *requires* that the result be copied.
-		return cstring_to_vstring(byteptr(s))
 	}
 }
 

vlib/os/fd.c.v

@@ -36,14 +36,14 @@ pub fn fd_slurp(fd int) []string {
 // read from filedescriptor, don't block
 // return [bytestring,nrbytes]
 pub fn fd_read(fd int, maxbytes int) (string, int) {
-	mut buf := malloc(maxbytes)
-	nbytes := C.read(fd, buf, maxbytes)
-	if nbytes < 0 {
-		free(buf)
-		return '', nbytes
-	}
 	unsafe {
+		mut buf := malloc(maxbytes)
+		nbytes := C.read(fd, buf, maxbytes)
+		if nbytes < 0 {
+			free(buf)
+			return '', nbytes
+		}
 		buf[nbytes] = 0
+		return tos(buf, nbytes), nbytes
 	}
-	return tos(buf, nbytes), nbytes
 }

vlib/os/os.v

@@ -600,8 +600,10 @@ pub fn resource_abs_path(path string) string {
 	}
 	fp := join_path(base_path, path)
 	res := real_path(fp)
-	fp.free()
-	base_path.free()
+	unsafe {
+		fp.free()
+		base_path.free()
+	}
 	return res
 }
 

vlib/os/os_c.v

@@ -715,21 +715,25 @@ pub fn chdir(path string) {
 pub fn getwd() string {
 	$if windows {
 		max := 512 // max_path_len * sizeof(wchar_t)
-		buf := &u16(vcalloc(max * 2))
-		if C._wgetcwd(buf, max) == 0 {
-			free(buf)
-			return ''
+		unsafe {
+			buf := &u16(vcalloc(max * 2))
+			if C._wgetcwd(buf, max) == 0 {
+				free(buf)
+				return ''
+			}
+			return string_from_wide(buf)
 		}
-		return string_from_wide(buf)
 	} $else {
 		buf := vcalloc(512)
-		if C.getcwd(charptr(buf), 512) == 0 {
+		unsafe {
+			if C.getcwd(charptr(buf), 512) == 0 {
+				free(buf)
+				return ''
+			}
+			res := buf.vstring().clone()
 			free(buf)
-			return ''
+			return res
 		}
-		res := unsafe { buf.vstring() }.clone()
-		free(buf)
-		return res
 	}
 }
 

vlib/os/os_nix.c.v

@@ -54,16 +54,18 @@ fn C.symlink(charptr, charptr) int
 pub fn uname() Uname {
 	mut u := Uname{}
 	utsize := sizeof(C.utsname)
-	x := malloc(int(utsize))
-	d := &C.utsname(x)
-	if C.uname(d) == 0 {
-		u.sysname = cstring_to_vstring(byteptr(d.sysname))
-		u.nodename = cstring_to_vstring(byteptr(d.nodename))
-		u.release = cstring_to_vstring(byteptr(d.release))
-		u.version = cstring_to_vstring(byteptr(d.version))
-		u.machine = cstring_to_vstring(byteptr(d.machine))
+	unsafe {
+		x := malloc(int(utsize))
+		d := &C.utsname(x)
+		if C.uname(d) == 0 {
+			u.sysname = cstring_to_vstring(byteptr(d.sysname))
+			u.nodename = cstring_to_vstring(byteptr(d.nodename))
+			u.release = cstring_to_vstring(byteptr(d.release))
+			u.version = cstring_to_vstring(byteptr(d.version))
+			u.machine = cstring_to_vstring(byteptr(d.machine))
+		}
+		free(d)
 	}
-	free(d)
 	return u
 }
 
@@ -166,9 +168,11 @@ pub fn exec(cmd string) ?Result {
 	}
 	buf := [4096]byte{}
 	mut res := strings.new_builder(1024)
-	for C.fgets(charptr(buf), 4096, f) != 0 {
-		bufbp := byteptr(buf)
-		res.write_bytes(bufbp, vstrlen(bufbp))
+	unsafe {
+		for C.fgets(charptr(buf), 4096, f) != 0 {
+			bufbp := byteptr(buf)
+			res.write_bytes(bufbp, vstrlen(bufbp))
+		}
 	}
 	soutput := res.str()
 	// res.free()