From Jason Turner

[cpp.concat]

C++23 → Trunk 2.9 KB 33 lines
Current Draft | LaTeX Source
Archived: C++23
Markdown: C++23 | Trunk
Explore in Adventure Game

Diff to HTML by rtfpessoa

Files changed (1) hide show
  1. tmp/tmp0i0os49r/{from.md → to.md} +13 -15
tmp/tmp0i0os49r/{from.md → to.md} RENAMED
@@ -6,31 +6,29 @@ end of a replacement list for either form of macro definition.
6
  If, in the replacement list of a function-like macro, a parameter is
7
  immediately preceded or followed by a `##` preprocessing token, the
8
  parameter is replaced by the corresponding argument’s preprocessing
9
  token sequence; however, if an argument consists of no preprocessing
10
  tokens, the parameter is replaced by a placemarker preprocessing token
11
- instead.[^8]
12
 
13
  For both object-like and function-like macro invocations, before the
14
  replacement list is reexamined for more macro names to replace, each
15
  instance of a `##` preprocessing token in the replacement list (not from
16
  an argument) is deleted and the preceding preprocessing token is
17
  concatenated with the following preprocessing token. Placemarker
18
  preprocessing tokens are handled specially: concatenation of two
19
  placemarkers results in a single placemarker preprocessing token, and
20
  concatenation of a placemarker with a non-placemarker preprocessing
21
- token results in the non-placemarker preprocessing token. If the result
22
- begins with a sequence matching the syntax of
23
- *universal-character-name*, the behavior is undefined.
24
 
25
- [*Note 1*: This determination does not consider the replacement of
26
- *universal-character-name*s in translation phase 3
27
- [[lex.phases]]. — *end note*]
28
 
29
- If the result is not a valid preprocessing token, the behavior is
30
- undefined. The resulting token is available for further macro
31
- replacement. The order of evaluation of `##` operators is unspecified.
 
32
 
33
  [*Example 1*:
34
 
35
  The sequence
36
 
@@ -71,12 +69,12 @@ fputs("strncmp(\"abc\\0d\", \"abc\", '\\4') == 0: \@n", s);
71
  #include "vers2.h" (after macro replacement, before file access)
72
  "hello";
73
  "hello, world"
74
  ```
75
 
76
- Space around the `#` and `##` tokens in the macro definition is
77
- optional.
78
 
79
  — *end example*]
80
 
81
  [*Example 2*:
82
 
@@ -98,13 +96,13 @@ in_between(x hash_hash y)
98
  in_between(x ## y)
99
  mkstr(x ## y)
100
  "x ## y"
101
  ```
102
 
103
- In other words, expanding `hash_hash` produces a new token, consisting
104
- of two adjacent sharp signs, but this new token is not the `##`
105
- operator.
106
 
107
  — *end example*]
108
 
109
  [*Example 3*:
110
 
 
6
  If, in the replacement list of a function-like macro, a parameter is
7
  immediately preceded or followed by a `##` preprocessing token, the
8
  parameter is replaced by the corresponding argument’s preprocessing
9
  token sequence; however, if an argument consists of no preprocessing
10
  tokens, the parameter is replaced by a placemarker preprocessing token
11
+ instead.[^7]
12
 
13
  For both object-like and function-like macro invocations, before the
14
  replacement list is reexamined for more macro names to replace, each
15
  instance of a `##` preprocessing token in the replacement list (not from
16
  an argument) is deleted and the preceding preprocessing token is
17
  concatenated with the following preprocessing token. Placemarker
18
  preprocessing tokens are handled specially: concatenation of two
19
  placemarkers results in a single placemarker preprocessing token, and
20
  concatenation of a placemarker with a non-placemarker preprocessing
21
+ token results in the non-placemarker preprocessing token.
 
 
22
 
23
+ [*Note 1*: Concatenation can form a *universal-character-name*
24
+ [[lex.charset]]. — *end note*]
 
25
 
26
+ If the result is not a valid preprocessing token, the program is
27
+ ill-formed. The resulting preprocessing token is available for further
28
+ macro replacement. The order of evaluation of `##` operators is
29
+ unspecified.
30
 
31
  [*Example 1*:
32
 
33
  The sequence
34
 
 
69
  #include "vers2.h" (after macro replacement, before file access)
70
  "hello";
71
  "hello, world"
72
  ```
73
 
74
+ Space around the `#` and `##` preprocessing tokens in the macro
75
+ definition is optional.
76
 
77
  — *end example*]
78
 
79
  [*Example 2*:
80
 
 
96
  in_between(x ## y)
97
  mkstr(x ## y)
98
  "x ## y"
99
  ```
100
 
101
+ In other words, expanding `hash_hash` produces a new preprocessing
102
+ token, consisting of two adjacent sharp signs, but this new
103
+ preprocessing token is not the `##` operator.
104
 
105
  — *end example*]
106
 
107
  [*Example 3*:
108