cgen: cast 'vstring'.str to char * if it is the expected type

vlib/net/mbedtls/mbedtls.c.v

@@ -163,14 +163,14 @@ fn C.mbedtls_entropy_free(&C.mbedtls_entropy_context)
 
 fn C.mbedtls_ssl_config_defaults(&C.mbedtls_ssl_config, int, int, int) int
 
-fn C.mbedtls_x509_crt_parse(&C.mbedtls_x509_crt, &char, int) int
-fn C.mbedtls_pk_parse_key(&C.mbedtls_pk_context, &char, int, &char, int, voidptr, voidptr) int
+fn C.mbedtls_x509_crt_parse(&C.mbedtls_x509_crt, &u8, int) int
+fn C.mbedtls_pk_parse_key(&C.mbedtls_pk_context, &u8, int, &char, int, voidptr, voidptr) int
 fn C.mbedtls_x509_crt_parse_file(&C.mbedtls_x509_crt, &char) int
 fn C.mbedtls_pk_parse_keyfile(&C.mbedtls_pk_context, &char, &char, voidptr, voidptr) int
 
-fn C.mbedtls_net_connect(&C.mbedtls_net_context, &u8, &u8, int) int
+fn C.mbedtls_net_connect(&C.mbedtls_net_context, &char, &char, int) int
 
-fn C.mbedtls_net_bind(&C.mbedtls_net_context, voidptr, &u8, int) int
+fn C.mbedtls_net_bind(&C.mbedtls_net_context, voidptr, &char, int) int
 fn C.mbedtls_net_accept(&C.mbedtls_net_context, &C.mbedtls_net_context, voidptr, int, voidptr) int
 fn C.mbedtls_ssl_session_reset(&C.mbedtls_ssl_context)
 fn C.mbedtls_ssl_conf_authmode(&C.mbedtls_ssl_config, int)
@@ -188,8 +188,8 @@ fn C.mbedtls_ssl_set_bio(&C.mbedtls_ssl_context, &C.mbedtls_net_context, voidptr
 
 fn C.mbedtls_ssl_handshake(&C.mbedtls_ssl_context) int
 
-fn C.mbedtls_ssl_read(&C.mbedtls_ssl_context, &char, int) int
-fn C.mbedtls_ssl_write(&C.mbedtls_ssl_context, &char, int) int
+fn C.mbedtls_ssl_read(&C.mbedtls_ssl_context, &u8, int) int
+fn C.mbedtls_ssl_write(&C.mbedtls_ssl_context, &u8, int) int
 
 fn C.mbedtls_high_level_strerr(int) &char
 

vlib/v/gen/c/cgen.v

@@ -2544,14 +2544,17 @@ fn (mut g Gen) expr_with_cast(expr ast.Expr, got_type_raw ast.Type, expected_typ
 		g.write('->val')
 		return
 	}
-	if got_is_ptr && !expected_is_ptr && neither_void && exp_sym.kind != .placeholder
-		&& expr !is ast.InfixExpr {
-		got_deref_type := got_type.deref()
-		deref_sym := g.table.sym(got_deref_type)
-		deref_will_match := expected_type in [got_type, got_deref_type, deref_sym.parent_idx]
-		got_is_opt_or_res := got_type.has_flag(.option) || got_type.has_flag(.result)
-		if deref_will_match || got_is_opt_or_res || expr.is_auto_deref_var() {
-			g.write('*')
+	if got_is_ptr && neither_void && exp_sym.kind != .placeholder && expr !is ast.InfixExpr {
+		if !expected_is_ptr {
+			got_deref_type := got_type.deref()
+			deref_sym := g.table.sym(got_deref_type)
+			deref_will_match := expected_type in [got_type, got_deref_type, deref_sym.parent_idx]
+			got_is_opt_or_res := got_type.has_flag(.option) || got_type.has_flag(.result)
+			if deref_will_match || got_is_opt_or_res || expr.is_auto_deref_var() {
+				g.write('*')
+			}
+		} else if expr !is ast.StringLiteral && exp_sym.kind == .char && got_sym.kind == .u8 {
+			g.write('(${exp_styp})')
 		}
 	}
 	if expr is ast.IntegerLiteral {

vlib/v/gen/c/testdata/c_fn_args.out

@@ -0,0 +1 @@
+barbaz

vlib/v/gen/c/testdata/c_fn_args.vv

@@ -0,0 +1,9 @@
+fn foo(bar &char, baz &char) {
+	println(unsafe { bar.vstring() + baz.vstring() })
+}
+
+fn main() {
+	baz := 'baz'.str
+	// Should compile with `-cc [gcc/clang] -cstrict`
+	foo('bar'.str, baz)
+}