cgen: fix _str name generated for C struct which define str() method (#…

…21042)

vlib/v/gen/c/auto_str_methods.v

@@ -83,6 +83,9 @@ fn (mut g Gen) get_str_fn(typ ast.Type) string {
 			else {}
 		}
 	}
+	if sym.language == .c && !typ.has_flag(.option) && sym.has_method('str') {
+		str_fn_name = util.no_dots(g.cc_type(unwrapped, false)) + '_str'
+	}
 	g.str_types << StrType{
 		typ: unwrapped
 		styp: styp

vlib/v/tests/c_structs/cstruct.h

@@ -0,0 +1,4 @@
+
+struct Abc {
+   int field;
+};

vlib/v/tests/c_structs/cstruct_test.c.v

@@ -0,0 +1,17 @@
+#include "@VMODROOT/cstruct.h"
+
+const the_string = 'the string'
+
+pub struct C.Abc {
+	field int
+}
+
+fn (a &C.Abc) str() string {
+	return 'C.Abc{}'
+}
+
+fn test_cstruct() {
+	x := unsafe { &C.Abc(1) }
+	println(x)
+	assert dump(x.str()) == 'C.Abc{}'
+}