Issue 260428.1: Accessibility Declarations for FreePascal

Author:	Martin Friebe
Champion:	Ben Woodard
Date submitted:	2026-04-28
Date revised:	2026-10-23
Date closed:
Type:	Enhancement
Status:	Open
DWARF version:	6

Issue

DWARF Version 5 only has Accessibility declarations DW_ACCESS_public, DW_ACCESS_private, and DW_ACCESS_protected. However, Free Pascal defines additional visibility specifiers that need representation. This addition allows debuggers to report member accessibility accurately to users and enables ABI checkers like libabigail to detect API changes that affect the ABI of an object.

The full list can be found in the Free Pascal Reference Guide.

In the documentation for Free Pascal, the terminology that they currently use literally uses the word "visibility". This led to some confusion and this topic was extensively researched. The conclusion that we arrived at is that in the Pascal community it is customary to use the word "visibility" in a way where it is synonymous with the DWARF concept of accessibility. This use should not be confused with ELF symbol visibility or the DWARF concept of visibility. It is just historical and customary in Pascal community to use "visibility" and "accessibility" interchangeably.

Published

Free Pascal also has a concept of "published". This topic was also researched extensively. The graphical GUI editor for the extension to Pascal called Delphi that Free Pascal was derived from relied on Run Time Type Information (RTTI) to associate graphical widgets with classes that implemented their functionality. The Free Pascal compiler uses the "published" keyword to instruct the compiler to include this RTTI information with the class. It was determined that the concept is not related to the DWARF concept of access.

Other compilers for languages including C++ also selectively include RTTI information for classes. Therefore, it was decided to add a new attribute DW_AT_rtti that Free Pascal can use in conjunction with DW_ACCESS_public to indicate, that the class is "published". It should be noted that even though C++ does selectively emit RTTI information, there is no currently known demonstrated need for DW_AT_rtti by C++ producers or consumers. Never the less, we believe that DW_AT_rtti may prove to be more generally useful than DW_AT_published which likely would only be used by Free Pascal.

Proposal

In Section 2.2 in Table 2.2 add:

Attribute	Usage
DW_AT_rtti	Objects or types have Run Time Type Information

In Section 2.7:

Add Pascal to the list of languages which have Accessibility of Declarations so that it reads:

Some languages, notably C++, Ada, and some dialects of Pascal, have the concept of the accessibility of an object or of some other program entity. The accessibility specifies which classes of other program objects are permitted access to the object in question.

Just before the table in Section 2.7 add this paragraph:

The precise meaning and semantics of these codes must be interpreted in the context of the rules of source language where the declaration is made.

In Table 2.4 add two more accessibility codes and add second column with their meaning:

Accessibility code name	Meaning
DW_ACCESS_public	The declaration can be used anywhere without access restriction.
DW_ACCESS_private	The declaration can be used only by members and friends of the class in which it is declared.
DW_ACCESS_protected	The declaration can be used only by members and friends of the class in which it is declared, by classes derived from that class, and by their friends.
DW_ACCESS_module_private	The declaration can only be accessed in the module that contains the declaration.
DW_ACCESS_module_protected	The declaration can only be accessed within module that contains the declaration, or by the members and friends of the class in which it is declared, or by classes derived from that class, and by their friends.
DW_ACCESS_published	Similar in access policy to public with additonal RTTI information preserved for visual programming.

Then later on in Chapter 2 possibly between 2.9 Virtuality of Declarations and 2.10 Artificial Entries add a new Section:

2.N Run Time Type Information

Several languages (such as Free Pascal) need to indicate when an entity such as a class has Run Time Type Information (RTTI) available.

If a declaration includes instructions to the compiler that an entity such as a class has Run Time Type Information, then DW_AT_rtti may be used.

In section 8.5.4 Attribute Encodings Table 8.5 add:

Attribute Name	Value	Classes
DW_AT_rtti	TBD	flag

In Section 8.9 Add the following entries to table 8.14:

Accessibility code name	Value
DW_ACCESS_module_private	TBD
DW_ACCESS_module_protected	TBD

---

2026-05-10: Added DW_ACCESS_published for completeness.

2026-09-24: Added Pascal to non-normative text listing languages that have accessibility attributes.

2026-09-29: Removed DW_ACCESS_strict_private/protected and added DW_ACCESS_module_private/protected; Added basic semantics of different policies.

2026-10-23: Revised. Replaced "published" accessibility code with a new DW_AT_rtti attribute. Fixed incorrect description for DW_ACCESS_module_protected.