`#min_field_align` & `#max_field_align`; deprecate `#field_align` in favour of `#min_field_align`

4 files changed, 74 insertions, 22 deletions

diff --git a/src/check_type.cpp b/src/check_type.cpp
index f0e0acb9b..bbeff9ca7 100644
--- a/src/check_type.cpp
+++ b/src/check_type.cpp
@@ -673,7 +673,7 @@ gb_internal void check_struct_type(CheckerContext *ctx, Type *struct_type, Ast *
 
 #define ST_ALIGN(_name) if (st->_name != nullptr) {                                                \
 		if (st->is_packed) {                                                               \
-			syntax_error(st->_name, "'#%s' cannot be applied with '#packed'", #_name); \
+			error(st->_name, "'#%s' cannot be applied with '#packed'", #_name); \
 			return;                                                                    \
 		}                                                                                  \
 		i64 align = 1;                                                                     \
@@ -682,12 +682,31 @@ gb_internal void check_struct_type(CheckerContext *ctx, Type *struct_type, Ast *
 		}                                                                                  \
 	}
 
-	ST_ALIGN(field_align);
+	ST_ALIGN(min_field_align);
+	ST_ALIGN(max_field_align);
 	ST_ALIGN(align);
-	if (struct_type->Struct.custom_align < struct_type->Struct.custom_field_align) {
-		warning(st->align, "#align(%lld) is defined to be less than #field_name(%lld)",
-		        cast(long long)struct_type->Struct.custom_align,
-		        cast(long long)struct_type->Struct.custom_field_align);
+	if (struct_type->Struct.custom_align < struct_type->Struct.custom_min_field_align) {
+		error(st->align, "#align(%lld) is defined to be less than #min_field_align(%lld)",
+		      cast(long long)struct_type->Struct.custom_align,
+		      cast(long long)struct_type->Struct.custom_min_field_align);
+	}
+	if (struct_type->Struct.custom_max_field_align != 0 &&
+	    struct_type->Struct.custom_align > struct_type->Struct.custom_max_field_align) {
+		error(st->align, "#align(%lld) is defined to be greater than #max_field_align(%lld)",
+		      cast(long long)struct_type->Struct.custom_align,
+		      cast(long long)struct_type->Struct.custom_max_field_align);
+	}
+	if (struct_type->Struct.custom_max_field_align != 0 &&
+	    struct_type->Struct.custom_min_field_align > struct_type->Struct.custom_max_field_align) {
+		error(st->align, "#min_field_align(%lld) is defined to be greater than #max_field_align(%lld)",
+		      cast(long long)struct_type->Struct.custom_min_field_align,
+		      cast(long long)struct_type->Struct.custom_max_field_align);
+
+		i64 a = gb_min(struct_type->Struct.custom_min_field_align, struct_type->Struct.custom_max_field_align);
+		i64 b = gb_max(struct_type->Struct.custom_min_field_align, struct_type->Struct.custom_max_field_align);
+		// NOTE(bill): sort them to keep code consistent
+		struct_type->Struct.custom_min_field_align = a;
+		struct_type->Struct.custom_max_field_align = b;
 	}
 
 #undef ST_ALIGN
diff --git a/src/parser.cpp b/src/parser.cpp
index 5b4604c6d..4029d49de 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -448,7 +448,8 @@ gb_internal Ast *clone_ast(Ast *node, AstFile *f) {
 		n->StructType.fields             = clone_ast_array(n->StructType.fields, f);
 		n->StructType.polymorphic_params = clone_ast(n->StructType.polymorphic_params, f);
 		n->StructType.align              = clone_ast(n->StructType.align, f);
-		n->StructType.field_align        = clone_ast(n->StructType.field_align, f);
+		n->StructType.min_field_align    = clone_ast(n->StructType.min_field_align, f);
+		n->StructType.max_field_align    = clone_ast(n->StructType.max_field_align, f);
 		n->StructType.where_clauses      = clone_ast_array(n->StructType.where_clauses, f);
 		break;
 	case Ast_UnionType:
@@ -1217,7 +1218,7 @@ gb_internal Ast *ast_dynamic_array_type(AstFile *f, Token token, Ast *elem) {
 
 gb_internal Ast *ast_struct_type(AstFile *f, Token token, Slice<Ast *> fields, isize field_count,
                      Ast *polymorphic_params, bool is_packed, bool is_raw_union, bool is_no_copy,
-                     Ast *align, Ast *field_align,
+                     Ast *align, Ast *min_field_align, Ast *max_field_align,
                      Token where_token, Array<Ast *> const &where_clauses) {
 	Ast *result = alloc_ast_node(f, Ast_StructType);
 	result->StructType.token              = token;
@@ -1228,7 +1229,8 @@ gb_internal Ast *ast_struct_type(AstFile *f, Token token, Slice<Ast *> fields, i
 	result->StructType.is_raw_union       = is_raw_union;
 	result->StructType.is_no_copy         = is_no_copy;
 	result->StructType.align              = align;
-	result->StructType.field_align        = field_align;
+	result->StructType.min_field_align    = min_field_align;
+	result->StructType.max_field_align    = max_field_align;
 	result->StructType.where_token        = where_token;
 	result->StructType.where_clauses      = slice_from_array(where_clauses);
 	return result;
@@ -2757,7 +2759,8 @@ gb_internal Ast *parse_operand(AstFile *f, bool lhs) {
 		bool is_raw_union       = false;
 		bool no_copy            = false;
 		Ast *align              = nullptr;
-		Ast *field_align        = nullptr;
+		Ast *min_field_align    = nullptr;
+		Ast *max_field_align    = nullptr;
 
 		if (allow_token(f, Token_OpenParen)) {
 			isize param_count = 0;
@@ -2795,18 +2798,43 @@ gb_internal Ast *parse_operand(AstFile *f, bool lhs) {
 					gb_string_free(s);
 				}
 			} else if (tag.string == "field_align") {
-				if (field_align) {
+				if (min_field_align) {
 					syntax_error(tag, "Duplicate struct tag '#%.*s'", LIT(tag.string));
 				}
-				field_align = parse_expr(f, true);
-				if (field_align && field_align->kind != Ast_ParenExpr) {
+				syntax_warning(tag, "#field_align has been deprecated in favour of #min_field_align");
+				min_field_align = parse_expr(f, true);
+				if (min_field_align && min_field_align->kind != Ast_ParenExpr) {
 					ERROR_BLOCK();
-					gbString s = expr_to_string(field_align);
+					gbString s = expr_to_string(min_field_align);
 					syntax_warning(tag, "#field_align requires parentheses around the expression");
-					error_line("\tSuggestion: #field_align(%s)", s);
+					error_line("\tSuggestion: #min_field_align(%s)", s);
 					gb_string_free(s);
 				}
-			} else if (tag.string == "raw_union") {
+			} else if (tag.string == "min_field_align") {
+				if (min_field_align) {
+					syntax_error(tag, "Duplicate struct tag '#%.*s'", LIT(tag.string));
+				}
+				min_field_align = parse_expr(f, true);
+				if (min_field_align && min_field_align->kind != Ast_ParenExpr) {
+					ERROR_BLOCK();
+					gbString s = expr_to_string(min_field_align);
+					syntax_warning(tag, "#min_field_align requires parentheses around the expression");
+					error_line("\tSuggestion: #min_field_align(%s)", s);
+					gb_string_free(s);
+				}
+			} else if (tag.string == "max_field_align") {
+				if (max_field_align) {
+					syntax_error(tag, "Duplicate struct tag '#%.*s'", LIT(tag.string));
+				}
+				max_field_align = parse_expr(f, true);
+				if (max_field_align && max_field_align->kind != Ast_ParenExpr) {
+					ERROR_BLOCK();
+					gbString s = expr_to_string(max_field_align);
+					syntax_warning(tag, "#max_field_align requires parentheses around the expression");
+					error_line("\tSuggestion: #max_field_align(%s)", s);
+					gb_string_free(s);
+				}
+			}else if (tag.string == "raw_union") {
 				if (is_raw_union) {
 					syntax_error(tag, "Duplicate struct tag '#%.*s'", LIT(tag.string));
 				}
@@ -2856,7 +2884,7 @@ gb_internal Ast *parse_operand(AstFile *f, bool lhs) {
 
 		parser_check_polymorphic_record_parameters(f, polymorphic_params);
 
-		return ast_struct_type(f, token, decls, name_count, polymorphic_params, is_packed, is_raw_union, no_copy, align, field_align, where_token, where_clauses);
+		return ast_struct_type(f, token, decls, name_count, polymorphic_params, is_packed, is_raw_union, no_copy, align, min_field_align, max_field_align, where_token, where_clauses);
 	} break;
 
 	case Token_union: {
diff --git a/src/parser.hpp b/src/parser.hpp
index d5117a31e..e332fed50 100644
--- a/src/parser.hpp
+++ b/src/parser.hpp
@@ -736,7 +736,8 @@ AST_KIND(_TypeBegin, "", bool) \
 		isize field_count;          \
 		Ast *polymorphic_params;    \
 		Ast *align;                 \
-		Ast *field_align;           \
+		Ast *min_field_align;       \
+		Ast *max_field_align;       \
 		Token where_token;          \
 		Slice<Ast *> where_clauses; \
 		bool is_packed;             \
diff --git a/src/types.cpp b/src/types.cpp
index a9a7d6dda..ec9917506 100644
--- a/src/types.cpp
+++ b/src/types.cpp
@@ -137,7 +137,8 @@ struct TypeStruct {
 	Scope *         scope;
 
 	i64             custom_align;
-	i64             custom_field_align;
+	i64             custom_min_field_align;
+	i64             custom_max_field_align;
 	Type *          polymorphic_params; // Type_Tuple
 	Type *          polymorphic_parent;
 	Wait_Signal     polymorphic_wait_signal;
@@ -3950,7 +3951,7 @@ gb_internal i64 type_align_of_internal(Type *t, TypePath *path) {
 	return gb_clamp(next_pow2(type_size_of_internal(t, path)), 1, build_context.max_align);
 }
 
-gb_internal i64 *type_set_offsets_of(Slice<Entity *> const &fields, bool is_packed, bool is_raw_union, i64 min_field_align) {
+gb_internal i64 *type_set_offsets_of(Slice<Entity *> const &fields, bool is_packed, bool is_raw_union, i64 min_field_align, i64 max_field_align) {
 	gbAllocator a = permanent_allocator();
 	auto offsets = gb_alloc_array(a, i64, fields.count);
 	i64 curr_offset = 0;
@@ -3980,6 +3981,9 @@ gb_internal i64 *type_set_offsets_of(Slice<Entity *> const &fields, bool is_pack
 			} else {
 				Type *t = fields[i]->type;
 				i64 align = gb_max(type_align_of(t), min_field_align);
+				if (max_field_align > min_field_align) {
+					align = gb_min(align, max_field_align);
+				}
 				i64 size  = gb_max(type_size_of( t), 0);
 				curr_offset = align_formula(curr_offset, align);
 				offsets[i] = curr_offset;
@@ -3996,7 +4000,7 @@ gb_internal bool type_set_offsets(Type *t) {
 		MUTEX_GUARD(&t->Struct.offset_mutex);
 		if (!t->Struct.are_offsets_set) {
 			t->Struct.are_offsets_being_processed = true;
-			t->Struct.offsets = type_set_offsets_of(t->Struct.fields, t->Struct.is_packed, t->Struct.is_raw_union, t->Struct.custom_field_align);
+			t->Struct.offsets = type_set_offsets_of(t->Struct.fields, t->Struct.is_packed, t->Struct.is_raw_union, t->Struct.custom_min_field_align, t->Struct.custom_max_field_align);
 			t->Struct.are_offsets_being_processed = false;
 			t->Struct.are_offsets_set = true;
 			return true;
@@ -4005,7 +4009,7 @@ gb_internal bool type_set_offsets(Type *t) {
 		MUTEX_GUARD(&t->Tuple.mutex);
 		if (!t->Tuple.are_offsets_set) {
 			t->Tuple.are_offsets_being_processed = true;
-			t->Tuple.offsets = type_set_offsets_of(t->Tuple.variables, t->Tuple.is_packed, false, 1);
+			t->Tuple.offsets = type_set_offsets_of(t->Tuple.variables, t->Tuple.is_packed, false, 1, 0);
 			t->Tuple.are_offsets_being_processed = false;
 			t->Tuple.are_offsets_set = true;
 			return true;