cgen: fix code generation for a struct field, having a type of fixed array of options field [5]?Type (#21082)

Author: felipensp

vlib/v/gen/c/cgen.v

@@ -1473,12 +1473,20 @@ pub fn (mut g Gen) write_typedef_types() {
 							def_str = def_str.replace_once('(*)', '(*${styp}[${len}])')
 							g.type_definitions.writeln(def_str)
 						} else if !info.is_fn_ret {
-							g.type_definitions.writeln('typedef ${fixed} ${styp} [${len}];')
 							base := g.typ(info.elem_type.clear_option_and_result())
 							if info.elem_type.has_flag(.option) && base !in g.options_forward {
-								g.options_forward << base
-							} else if info.elem_type.has_flag(.result) && base !in g.results_forward {
-								g.results_forward << base
+								lock g.done_options {
+									if base !in g.done_options {
+										g.type_definitions.writeln('typedef ${fixed} ${styp} [${len}];')
+										g.options_forward << base
+										g.done_options << styp
+									}
+								}
+							} else {
+								g.type_definitions.writeln('typedef ${fixed} ${styp} [${len}];')
+								if info.elem_type.has_flag(.result) && base !in g.results_forward {
+									g.results_forward << base
+								}
 							}
 						}
 					}
@@ -6396,6 +6404,27 @@ fn (mut g Gen) write_types(symbols []&ast.TypeSymbol) {
 		match sym.info {
 			ast.Struct {
 				if !struct_names[name] {
+					// generate field option types for fixed array of option struct before struct declaration
+					opt_fields := sym.info.fields.filter(g.table.final_sym(it.typ).kind == .array_fixed)
+					for opt_field in opt_fields {
+						field_sym := g.table.final_sym(opt_field.typ)
+						arr := field_sym.info as ast.ArrayFixed
+						if !arr.elem_type.has_flag(.option) {
+							continue
+						}
+						styp := field_sym.cname
+						mut fixed_elem_name := g.typ(arr.elem_type.set_nr_muls(0))
+						if arr.elem_type.is_ptr() {
+							fixed_elem_name += '*'.repeat(arr.elem_type.nr_muls())
+						}
+						len := arr.size
+						lock g.done_options {
+							if styp !in g.done_options {
+								g.type_definitions.writeln('typedef ${fixed_elem_name} ${styp} [${len}];')
+								g.done_options << styp
+							}
+						}
+					}
 					g.struct_decl(sym.info, name, false)
 					struct_names[name] = true
 				}
@@ -6479,7 +6508,20 @@ fn (mut g Gen) write_types(symbols []&ast.TypeSymbol) {
 							g.type_definitions.writeln(def_str)
 						} else if elem_sym.info !is ast.ArrayFixed
 							|| (elem_sym.info as ast.ArrayFixed).size > 0 {
-							g.type_definitions.writeln('typedef ${fixed_elem_name} ${styp} [${len}];')
+							// fixed array of option struct must be defined backwards
+							if sym.info.elem_type.has_flag(.option) && elem_sym.info is ast.Struct {
+								styp_elem, base := g.option_type_name(sym.info.elem_type)
+								lock g.done_options {
+									if base !in g.done_options {
+										g.done_options << base
+										g.typedefs.writeln('typedef struct ${styp_elem} ${styp_elem};')
+										g.type_definitions.writeln('${g.option_type_text(styp_elem,
+											base)};')
+									}
+								}
+							} else {
+								g.type_definitions.writeln('typedef ${fixed_elem_name} ${styp} [${len}];')
+							}
 						}
 					}
 				}

vlib/v/tests/option_array_fixed_struct_test.v

@@ -0,0 +1,16 @@
+struct Test {}
+
+struct Test2 {
+	a [10]?Test
+}
+
+struct Test3 {
+	a [10]?Test
+}
+
+fn test_main() {
+	a := Test2{}
+	b := Test3{}
+	assert dump(Test2{}) == a
+	assert dump(Test3{}) == b
+}