Re: What is a header?

From: Kevin Goodsell (usenet2.spamfree.fusion_at_neverbox.com)
Date: 04/01/04 

Date: Thu, 01 Apr 2004 21:07:48 GMT

Julie wrote:

> "Steven T. Hatton" wrote:
>
>>If a header is not necessarily a source file, and the sequences delimited by
>>< and > in header names aren't necessarily valid source file names, what
>>exactly is a header?
>
>
> A header is _necessarily_ a source file that is exclusively distinctly visible
> by the preprocessor.

   2.8 Header names [lex.header]
   header-name:
           <h-char-sequence>
           "q-char-sequence"
   h-char-sequence:
           h-char
           h-char-sequence h-char
   h-char:
           any member of the source character set except
                   new-line and >
   q-char-sequence:
           q-char
           q-char-sequence q-char
   q-char:
           any member of the source character set except
                   new-line and "

1 Header name preprocessing tokens shall only appear within a #include
   preprocessing directive (_cpp.include_). The sequences in both forms
   of header-names are mapped in an implementation-defined manner to
   headers or to external source file names as specified in
   _cpp.include_.

   16.2 Source file inclusion [cpp.include]

1 A #include directive shall identify a header or source file that can
   be processed by the implementation.

2 A preprocessing directive of the form
   # include <h-char-sequence> new-line
   searches a sequence of implementation-defined places for a header
   identified uniquely by the specified sequence between the < and >
   delimiters, and causes the replacement of that directive by the entire
   contents of the header. How the places are specified or the header
   identified is implementation-defined.

I don't see anything here requiring headers to be files. In fact, it
sounds like they went out of their way to make sure that was not implied
(e.g., "header _or_ source file").

-Kevin 

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