Type Compatibility: Ghosts, Readability, and A Missing Rule for Atomic

Preamble

contributing

Martin Uecker (rationale, history, wording)

Joseph Myers, Robert Seacord, Jens Gustedt (wording)

rationale

This removes misleading “shall” that does not indicate undefined behavior and adds a missing rule for atomic. A previous version of this paper N3742 received strong support and was sent to the wording group. In the discussion, it was noted that additional statements about qualified and atomic types and compatibility may be needed.

Related documents

LaTeX document branch

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Liaison

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Relevant polls

Along the lines of n3742

Proposed wording

Legend

Deletions in the shown standard text are as shown here, additions, as shown here. These may render differently according to the style in which the document is shown by your browser, but should always be well distinguishable. In the provided style there are two visual distinctions:

• A high contrast color palete (Okabe and Ito) namely using colors black, orange, teal green and light yellow
• normal text, strike through, underlining and typewriter font.

Close to each other proposed changes resemble like this.

Modifications in subclause 6.7.4.1

11 Two qualified types are compatible if and only if they are identically qualified versions of compatible types; the order of type qualifiers within a list of specifiers or qualifiers does not affect the specified type. A qualified type is incompatible with an unqualified type. An atomic type is incompatible with a non-atomic type.

Modifications in subclause 6.7.7.2

6.7.7.2 Pointer declarators

Semantics

2 For two pointer types to be compatible, both shall be identically qualified and both shall be pointers to compatible types. Two unqualified, non-atomic pointer types are compatible if and only if both are pointers to compatible types.

Modifications in subclause 6.7.3.5

Semantics

4 …

4′ Two atomic types are compatible if and only if the corresponding non-atomic types are compatible.