Defect Report #169
Submis>sion Date: 16 Oct 95
Submittor: BSI
Source: Clive D.W. Feather
Question
Submitted to BSI by Clive D.W. Feather clive@sco.com .
In this Defect Report, identifiers lexically identical to those
declared in standard headers refer to the identifiers declared in those
standard headers, whether or not the header is explicitly mentioned.
This Defect Report has been prepared with considerable help from
Mark Brader, Jutta Degener, Ronald Guilmette, and a person whose
employment conditions require anonymity. However, except where stated,
opinions expressed or implied should not be assumed to be those of any
person other than myself.
Defect Report UK 017: Trigraphs
The C Standard's description of the replacement of trigraphs is
contradictory.
Subclause 5.2.1.1 reads in part:
All occurrences in a source file of the following sequences of
three characters (called trigraph sequences [7]) are replaced with the
corresponding single character... Each ? that does not
begin one of the trigraphs listed above is not changed.
Since the second character in each trigraph is a ?
that does not begin the trigraph, this is a direct contradiction.
Suggested Technical Corrigendum
Change the last sentence of the cited text to:
Each ? that is not part of one of the trigraphs
listed above is not changed.
Proposed Response
The C Standard is clear enough as is. A trigraph begins with two
question marks, so it is reasonable to refer to both of them as
beginning the trigraph.
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