[cpp.include] - C++23 → Trunk

Files changed (1) hide show

tmp/tmpw1ay24up/{from.md → to.md} +52 -33

tmp/tmpw1ay24up/{from.md → to.md} RENAMED Viewed

@@ -1,58 +1,77 @@
 ## Source file inclusion <a id="cpp.include">[[cpp.include]]</a>
-A `#include` directive shall identify a header or source file that can
-be processed by the implementation.
-A preprocessing directive of the form
-``` bnf
-'# 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*.
 A preprocessing directive of the form
 ``` bnf
-'# include "' q-char-sequence '"' new-line
 ```
 causes the replacement of that directive by the entire contents of the
-source file identified by the specified sequence between the `"`
-delimiters. The named source file is searched for in an
-*implementation-defined* manner. If this search is not supported, or if
-the search fails, the directive is reprocessed as if it read
 ``` bnf
-'# include <' h-char-sequence '>' new-line
 ```
-with the identical contained sequence (including `>` characters, if any)
-from the original directive.
 A preprocessing directive of the form
 ``` bnf
 '# include' pp-tokens new-line
 ```
-(that does not match one of the two previous forms) is permitted. The
-preprocessing tokens after `include` in the directive are processed just
-as in normal text (i.e., each identifier currently defined as a macro
-name is replaced by its replacement list of preprocessing tokens). If
-the directive resulting after all replacements does not match one of the
-two previous forms, the behavior is undefined.[^4]
-The method by which a sequence of preprocessing tokens between a `<` and
-a `>` preprocessing token pair or a pair of `"` characters is combined
-into a single header name preprocessing token is
-*implementation-defined*.
 The implementation shall provide unique mappings for sequences
 consisting of one or more *nondigit*s or *digit*s [[lex.name]] followed
 by a period (`.`) and a single *nondigit*. The first character shall not
 be a *digit*. The implementation may ignore distinctions of alphabetical
@@ -66,14 +85,14 @@ If the header identified by the *header-name* denotes an importable
 header [[module.import]], it is *implementation-defined* whether the
 `#include` preprocessing directive is instead replaced by an `import`
 directive [[cpp.import]] of the form
 ``` bnf
-'import' header-name ';' new-line
 ```
-[*Note 1*:
 An implementation can provide a mechanism for making arbitrary source
 files available to the `< >` search. However, using the `< >` form for
 headers provided with the implementation and the `" "` form for sources
 outside the control of the implementation achieves wider portability.

 ## Source file inclusion <a id="cpp.include">[[cpp.include]]</a>
+A *header search* for a sequence of characters searches a sequence of
+places for a header identified uniquely by that sequence of characters.
+How the places are determined or the header identified is
+*implementation-defined*.
+A *source file search* for a sequence of characters attempts to identify
+a source file that is named by the sequence of characters. The named
+source file is searched for in an *implementation-defined* manner. If
+the implementation does not support a source file search for that
+sequence of characters, or if the search fails, the result of the source
+file search is the result of a header search for the same sequence of
+characters.
 A preprocessing directive of the form
 ``` bnf
+'# include' header-name new-line
 ```
 causes the replacement of that directive by the entire contents of the
+header or source file identified by *header-name*.
+If the *header-name* is of the form
+``` bnf
+'<' h-char-sequence '>'
+```
+a header is identified by a header search for the sequence of characters
+of the *h-char-sequence*.
+If the *header-name* is of the form
 ``` bnf
+'"' q-char-sequence '"'
 ```
+the source file or header is identified by a source file search for the
+sequence of characters of the *q-char-sequence*.
+If a header search fails, or if a source file search or header search
+identifies a header or source file that cannot be processed by the
+implementation, the program is ill-formed.
+[*Note 1*: If the header or source file cannot be processed, the
+program is ill-formed even when evaluating
+`__has_include`. — *end note*]
 A preprocessing directive of the form
 ``` bnf
 '# include' pp-tokens new-line
 ```
+(that does not match the previous form) is permitted. The preprocessing
+tokens after `include` in the directive are processed just as in normal
+text (i.e., each identifier currently defined as a macro name is
+replaced by its replacement list of preprocessing tokens). Then, an
+attempt is made to form a *header-name* preprocessing token
+[[lex.header]] from the whitespace and the characters of the spellings
+of the resulting sequence of preprocessing tokens; the treatment of
+whitespace is *implementation-defined*. If the attempt succeeds, the
+directive with the so-formed *header-name* is processed as specified for
+the previous form. Otherwise, the program is ill-formed, no diagnostic
+required.
+[*Note 2*: Adjacent *string-literal*s are not concatenated into a
+single *string-literal* (see the translation phases in  [[lex.phases]]);
+thus, an expansion that results in two *string-literal*s is an invalid
+directive. — *end note*]
 The implementation shall provide unique mappings for sequences
 consisting of one or more *nondigit*s or *digit*s [[lex.name]] followed
 by a period (`.`) and a single *nondigit*. The first character shall not
 be a *digit*. The implementation may ignore distinctions of alphabetical
 header [[module.import]], it is *implementation-defined* whether the
 `#include` preprocessing directive is instead replaced by an `import`
 directive [[cpp.import]] of the form
 ``` bnf
+import header-name ';' new-line
 ```
+[*Note 3*:
 An implementation can provide a mechanism for making arbitrary source
 files available to the `< >` search. However, using the `< >` form for
 headers provided with the implementation and the `" "` form for sources
 outside the control of the implementation achieves wider portability.

Diff to HTML by rtfpessoa