From b60966cd10425e14b37c44e26c3fef429bc7e3b3 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Wed, 5 Mar 2025 14:16:25 -0300
Subject: [PATCH] cgen: fix interface method list ordering to make test
 buildable with `g++` (fix #23701) (#23870)

---
 vlib/v/gen/c/cgen.v                            | 11 ++++++++---
 .../c/testdata/iface_method_order.c.must_have  | 18 ++++++++++++++++++
 vlib/v/gen/c/testdata/iface_method_order.vv    | 18 ++++++++++++++++++
 3 files changed, 44 insertions(+), 3 deletions(-)
 create mode 100644 vlib/v/gen/c/testdata/iface_method_order.c.must_have
 create mode 100644 vlib/v/gen/c/testdata/iface_method_order.vv

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 7b219f6463..b192e8b27c 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -7533,7 +7533,8 @@ fn (mut g Gen) interface_table() string {
 		methods_struct_name := 'struct _${interface_name}_interface_methods'
 		mut methods_struct_def := strings.new_builder(100)
 		methods_struct_def.writeln('${methods_struct_name} {')
-		inter_methods := inter_info.get_methods()
+		mut inter_methods := inter_info.get_methods()
+		inter_methods.sort(a < b)
 		mut methodidx := map[string]int{}
 		for k, method_name in inter_methods {
 			method := isym.find_method_with_generic_parent(method_name) or { continue }
@@ -7664,7 +7665,9 @@ static inline __shared__${interface_name} ${shared_fn_name}(__shared__${cctype}*
 				methods_struct.writeln('\t{')
 			}
 			if st == ast.voidptr_type || st == ast.nil_type {
-				for mname, _ in methodidx {
+				mut mnames := methodidx.keys()
+				mnames.sort(a < b)
+				for mname in mnames {
 					if g.pref.build_mode != .build_module {
 						methods_struct.writeln('\t\t._method_${c_fn_name(mname)} = (void*) 0,')
 					}
@@ -7721,7 +7724,9 @@ static inline __shared__${interface_name} ${shared_fn_name}(__shared__${cctype}*
 				}
 			}
 
-			for method in methods {
+			mut ordered_methods := methods.clone()
+			ordered_methods.sort(a.name < b.name)
+			for method in ordered_methods {
 				mut name := method.name
 				if method.generic_names.len > 0 && inter_info.parent_type.has_flag(.generic) {
 					parent_sym := g.table.sym(inter_info.parent_type)
diff --git a/vlib/v/gen/c/testdata/iface_method_order.c.must_have b/vlib/v/gen/c/testdata/iface_method_order.c.must_have
new file mode 100644
index 0000000000..a61aeb1faf
--- /dev/null
+++ b/vlib/v/gen/c/testdata/iface_method_order.c.must_have
@@ -0,0 +1,18 @@
+struct _main__Foo_interface_methods {
+void (*_method_a)(void* _);
+void (*_method_b)(void* _);
+};
+struct _main__Foo_interface_methods main__Foo_name_table[3] = {
+{
+._method_a = (void*) main__Bar_a_Interface_main__Foo_method_wrapper,
+._method_b = (void*) main__Bar_b_Interface_main__Foo_method_wrapper,
+},
+{
+._method_a = (void*) 0,
+._method_b = (void*) 0,
+},
+{
+._method_a = (void*) main__Baz_a_Interface_main__Foo_method_wrapper,
+._method_b = (void*) main__Baz_b_Interface_main__Foo_method_wrapper,
+},
+};
\ No newline at end of file
diff --git a/vlib/v/gen/c/testdata/iface_method_order.vv b/vlib/v/gen/c/testdata/iface_method_order.vv
new file mode 100644
index 0000000000..615d5dbee6
--- /dev/null
+++ b/vlib/v/gen/c/testdata/iface_method_order.vv
@@ -0,0 +1,18 @@
+interface Foo {
+	a()
+	b()
+}
+
+struct Bar implements Foo {
+}
+
+fn (b Bar) b() {}
+
+fn (b Bar) a() {}
+
+struct Baz implements Foo {
+}
+
+fn (b Baz) b() {}
+
+fn (b Baz) a() {}