v.gen.c: initialize closures in shared library mode (#20630)

vlib/v/gen/c/cgen.v

@@ -6191,6 +6191,9 @@ fn (mut g Gen) write_init_function() {
 		}
 		g.writeln('void _vinit_caller() {')
 		g.writeln('\tstatic bool once = false; if (once) {return;} once = true;')
+		if g.nr_closures > 0 {
+			g.writeln('\t__closure_init(); // vinit_caller()')
+		}
 		g.writeln('\t_vinit(0,0);')
 		g.writeln('}')
 

vlib/v/gen/c/cmain.v

@@ -98,7 +98,7 @@ fn (mut g Gen) gen_c_main_function_header() {
 	g.writeln('\tg_main_argc = ___argc;')
 	g.writeln('\tg_main_argv = ___argv;')
 	if g.nr_closures > 0 {
-		g.writeln('__closure_init();')
+		g.writeln('\t__closure_init(); // main()')
 	}
 }
 

vlib/v/gen/c/testdata/closure_shared_lib.c.must_have

@@ -0,0 +1,2 @@
+__closure_init(); // vinit_caller()
+__closure_init(); // main()

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

@@ -0,0 +1,8 @@
+// vtest vflags: -shared
+@[export: 'foo']
+fn show_foo(s &char) {
+	my_fn := fn [s] () {
+		_ = s
+	}
+	my_fn()
+}