Suggested resolution [SUPERSEDED]:

Add a new paragraph after 4.1.1 [intro.compliance.general] paragraph 2 as follows:

Although this document states only requirements on C++ implementations, those requirements are often easier to understand if they are phrased as requirements on programs, parts of programs, or execution of programs. Such requirements have the following meaning:

• If a program contains no violations of the rules in Clause Clause 5 [lex] through Clause Clause 32 [thread] and Annex D, a conforming implementation shall, within its resource limits as described in Annex B, accept and correctly execute [ Footnote: ... ] that program.
• If a program contains a violation of any diagnosable rule or an occurrence of a construct described in this document as “conditionally-supported” when the implementation does not support that construct, a conforming implementation shall issue at least one diagnostic message.
• If a program contains a violation of a rule for which no diagnostic is required, this document places no requirement on implementations with respect to that program.

[Note: ... — end note]

Furthermore, a conforming implementation

• shall not accept a translation unit containing a #error preprocessing directive (15.9 [cpp.error]) unless it is part of a group skipped by conditional inclusion (15.2 [cpp.cond]) and
• shall issue at least one diagnostic message for each #warning or #error preprocessing directive not following a #error preprocessing directive, ignoring #warning and #error preprocessing directives appearing in groups skipped by conditional inclusion.

For classes and class templates, ...