[cpp.pre] - C++23 → Trunk

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tmp/tmpgfjokd6e/{from.md → to.md} +95 -31

tmp/tmpgfjokd6e/{from.md → to.md} RENAMED Viewed

@@ -37,10 +37,11 @@ group-part:
 ``` bnf
 control-line:
     '# include' pp-tokens new-line
     pp-import
     '# define ' identifier replacement-list new-line
     '# define ' identifier lparen identifier-listₒₚₜ ')' replacement-list new-line
     '# define ' identifier lparen '... )' replacement-list new-line
     '# define ' identifier lparen identifier-list ', ... )' replacement-list new-line
     '# undef ' identifier new-line
@@ -63,12 +64,11 @@ if-group:
     '# ifndef ' identifier new-line groupₒₚₜ
 ```
 ``` bnf
 elif-groups:
-    elif-group
-    elif-groups elif-group
 ```
 ``` bnf
 elif-group:
     '# elif ' constant-expression new-line groupₒₚₜ
@@ -112,39 +112,86 @@ replacement-list:
     pp-tokensₒₚₜ
 ```
 ``` bnf
 pp-tokens:
-    preprocessing-token
-    pp-tokens preprocessing-token
 ```
 ``` bnf
 new-line:
     the new-line character
 ```
 A *preprocessing directive* consists of a sequence of preprocessing
 tokens that satisfies the following constraints: At the start of
-translation phase 4, the first token in the sequence, referred to as a
-*directive-introducing token*, begins with the first character in the
-source file (optionally after whitespace containing no new-line
-characters) or follows whitespace containing at least one new-line
-character, and is
 - a `#` preprocessing token, or
 - an `import` preprocessing token immediately followed on the same
-  logical line by a *header-name*, `<`, *identifier*, *string-literal*,
-  or `:` preprocessing token, or
 - a `module` preprocessing token immediately followed on the same
-  logical line by an *identifier*, `:`, or `;` preprocessing token, or
 - an `export` preprocessing token immediately followed on the same
-  logical line by one of the two preceding forms.
-The last token in the sequence is the first token within the sequence
-that is immediately followed by whitespace containing a new-line
-character.[^1]
 [*Note 1*: A new-line character ends the preprocessing directive even
 if it occurs within what would otherwise be an invocation of a
 function-like macro. — *end note*]
@@ -174,15 +221,38 @@ import ->               // not a preprocessing directive
 ```
 — *end example*]
 A sequence of preprocessing tokens is only a *text-line* if it does not
-begin with a directive-introducing token. A sequence of preprocessing
-tokens is only a *conditionally-supported-directive* if it does not
-begin with any of the directive names appearing after a `#` in the
-syntax. A *conditionally-supported-directive* is conditionally-supported
-with *implementation-defined* semantics.
 At the start of phase 4 of translation, the *group* of a
 *pp-global-module-fragment* shall contain neither a *text-line* nor a
 *pp-import*.
@@ -191,24 +261,18 @@ relaxed to allow any sequence of preprocessing tokens to occur between
 the directive name and the following new-line character.
 The only whitespace characters that shall appear between preprocessing
 tokens within a preprocessing directive (from just after the
 directive-introducing token through just before the terminating new-line
-character) are space and horizontal-tab (including spaces that have
-replaced comments or possibly other whitespace characters in translation
-phase 3).
-The implementation can process and skip sections of source files
-conditionally, include other source files, import macros from header
-units, and replace macros. These capabilities are called
-*preprocessing*, because conceptually they occur before translation of
-the resulting translation unit.
 The preprocessing tokens within a preprocessing directive are not
 subject to macro expansion unless otherwise stated.
-[*Example 2*:
 In:
 ``` cpp
 #define EMPTY

 ``` bnf
 control-line:
     '# include' pp-tokens new-line
     pp-import
+    '# embed ' pp-tokens new-line
     '# define ' identifier replacement-list new-line
     '# define ' identifier lparen identifier-listₒₚₜ ')' replacement-list new-line
     '# define ' identifier lparen '... )' replacement-list new-line
     '# define ' identifier lparen identifier-list ', ... )' replacement-list new-line
     '# undef ' identifier new-line
     '# ifndef ' identifier new-line groupₒₚₜ
 ```
 ``` bnf
 elif-groups:
+    elif-group elif-groupsₒₚₜ
 ```
 ``` bnf
 elif-group:
     '# elif ' constant-expression new-line groupₒₚₜ
     pp-tokensₒₚₜ
 ```
 ``` bnf
 pp-tokens:
+    preprocessing-token pp-tokensₒₚₜ
+```
+``` bnf
+embed-parameter-seq:
+    embed-parameter embed-parameter-seqₒₚₜ
+```
+``` bnf
+embed-parameter:
+    embed-standard-parameter
+    embed-prefixed-parameter
+```
+``` bnf
+embed-standard-parameter:
+    'limit' '(' pp-balanced-token-seq ')'
+    'prefix' '(' pp-balanced-token-seqₒₚₜ ')'
+    'suffix' '(' pp-balanced-token-seqₒₚₜ ')'
+    'if_empty' '(' pp-balanced-token-seqₒₚₜ ')'
+```
+``` bnf
+embed-prefixed-parameter:
+    identifier :: identifier
+    identifier :: identifier '(' pp-balanced-token-seqₒₚₜ ')'
+```
+``` bnf
+pp-balanced-token-seq:
+    pp-balanced-token pp-balanced-token-seqₒₚₜ
+```
+``` bnf
+pp-balanced-token:
+    '(' pp-balanced-token-seqₒₚₜ ')'
+    '[' pp-balanced-token-seqₒₚₜ ']'
+    '{' pp-balanced-token-seqₒₚₜ '}'
+    any pp-token except:
+       parenthesis (U+0028 (left parenthesis) and U+0029 (right parenthesis)),
+       bracket (U+005b (left square bracket) and U+005d (right square bracket)), or
+       brace (U+007b (left curly bracket) and U+007d (right curly bracket)).
 ```
 ``` bnf
 new-line:
     the new-line character
 ```
+The implementation can process and skip sections of source files
+conditionally, include other source files, import macros from header
+units, and replace macros. These capabilities are called
+*preprocessing*, because conceptually they occur before translation of
+the resulting translation unit.
 A *preprocessing directive* consists of a sequence of preprocessing
 tokens that satisfies the following constraints: At the start of
+translation phase 4, the first preprocessing token in the sequence,
+referred to as a *directive-introducing token*, begins with the first
+character in the source file (optionally after whitespace containing no
+new-line characters) or follows whitespace containing at least one
+new-line character, and is
 - a `#` preprocessing token, or
 - an `import` preprocessing token immediately followed on the same
+  logical source line by a *header-name*, `<`, *identifier*,
+ *string-literal*, or `:` preprocessing token, or
 - a `module` preprocessing token immediately followed on the same
+  logical source line by an *identifier*, `:`, or `;` preprocessing
+  token, or
 - an `export` preprocessing token immediately followed on the same
+  logical source line by one of the two preceding forms.
+The last preprocessing token in the sequence is the first preprocessing
+token within the sequence that is immediately followed by whitespace
+containing a new-line character.[^1]
 [*Note 1*: A new-line character ends the preprocessing directive even
 if it occurs within what would otherwise be an invocation of a
 function-like macro. — *end note*]
 ```
 — *end example*]
 A sequence of preprocessing tokens is only a *text-line* if it does not
+begin with a directive-introducing token.
+[*Example 2*:
+``` cpp
+using module = int;
+module i;               // not a text-line and not a control-line
+int foo() {
+  return i;
+}
+```
+The example is not a valid *preprocessing-file*.
+— *end example*]
+A sequence of preprocessing tokens is only a
+*conditionally-supported-directive* if it does not begin with any of the
+directive names appearing after a `#` in the syntax. A
+*conditionally-supported-directive* is conditionally-supported with
+*implementation-defined* semantics.
+If one of the *pp-tokens* of a `#embed` directive (before macro
+replacement) is the *identifier* `limit`, `prefix`, `suffix`, or
+`if_empty` and that *identifier* is defined as a macro
+[[cpp.replace.general]], the program is ill-formed. Any
+*embed-prefixed-parameter* is conditionally-supported, with
+*implementation-defined* semantics.
 At the start of phase 4 of translation, the *group* of a
 *pp-global-module-fragment* shall contain neither a *text-line* nor a
 *pp-import*.
 the directive name and the following new-line character.
 The only whitespace characters that shall appear between preprocessing
 tokens within a preprocessing directive (from just after the
 directive-introducing token through just before the terminating new-line
+character) are U+0020 (space) and U+0009 (character tabulation)
+(including spaces that have replaced comments or possibly other
+whitespace characters in translation phase 3).
 The preprocessing tokens within a preprocessing directive are not
 subject to macro expansion unless otherwise stated.
+[*Example 3*:
 In:
 ``` cpp
 #define EMPTY

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