Стандарт C++ 11, страница 10

The separate translation units of a program communicate (3.5) by (for example) calls to functionswhose identifiers have external linkage, manipulation of objects whose identifiers have external linkage, ormanipulation of data files. Translation units can be separately translated and then later linked to producean executable program (3.5). — end note ]2.21Phases of translation[lex.phases]The precedence among the syntax rules of translation is specified by the following phases.111. Physical source file characters are mapped, in an implementation-defined manner, to the basic sourcecharacter set (introducing new-line characters for end-of-line indicators) if necessary.

The set of physical source file characters accepted is implementation-defined. Trigraph sequences (2.4) are replacedby corresponding single-character internal representations. Any source file character not in the basicsource character set (2.3) is replaced by the universal-character-name that designates that character. (An implementation may use any internal encoding, so long as an actual extended characterencountered in the source file, and the same extended character expressed in the source file as auniversal-character-name (i.e., using the \uXXXX notation), are handled equivalently except where thisreplacement is reverted in a raw string literal.)2. Each instance of a backslash character (\) immediately followed by a new-line character is deleted,splicing physical source lines to form logical source lines.

Only the last backslash on any physicalsource line shall be eligible for being part of such a splice. If, as a result, a character sequence thatmatches the syntax of a universal-character-name is produced, the behavior is undefined. A source filethat is not empty and that does not end in a new-line character, or that ends in a new-line characterimmediately preceded by a backslash character before any such splicing takes place, shall be processedas if an additional new-line character were appended to the file.3.

The source file is decomposed into preprocessing tokens (2.5) and sequences of white-space characters(including comments). A source file shall not end in a partial preprocessing token or in a partial comment.12 Each comment is replaced by one space character. New-line characters are retained. Whethereach nonempty sequence of white-space characters other than new-line is retained or replaced by onespace character is unspecified. The process of dividing a source file’s characters into preprocessing tokens is context-dependent.

[ Example: see the handling of < within a #include preprocessing directive.— end example ]11) Implementations must behave as if these separate phases occur, although in practice different phases might be foldedtogether.12) A partial preprocessing token would arise from a source file ending in the first portion of a multi-character token thatrequires a terminating sequence of characters, such as a header-name that is missing the closing " or >. A partial commentwould arise from a source file ending with an unclosed /* comment.§ 2.2© ISO/IEC 2011 – All rights reserved17ISO/IEC 14882:2011(E)4. Preprocessing directives are executed, macro invocations are expanded, and _Pragma unary operatorexpressions are executed.

If a character sequence that matches the syntax of a universal-character-nameis produced by token concatenation (16.3.3), the behavior is undefined. A #include preprocessing directive causes the named header or source file to be processed from phase 1 through phase 4, recursively.All preprocessing directives are then deleted.5. Each source character set member in a character literal or a string literal, as well as each escapesequence and universal-character-name in a character literal or a non-raw string literal, is converted tothe corresponding member of the execution character set (2.14.3, 2.14.5); if there is no correspondingmember, it is converted to an implementation-defined member other than the null (wide) character.136.

Adjacent string literal tokens are concatenated.7. White-space characters separating tokens are no longer significant. Each preprocessing token is converted into a token. (2.7). The resulting tokens are syntactically and semantically analyzed and translated as a translation unit. [ Note: The process of analyzing and translating the tokens may occasionallyresult in one token being replaced by a sequence of other tokens (14.2). — end note ] [ Note: Sourcefiles, translation units and translated translation units need not necessarily be stored as files, nor needthere be any one-to-one correspondence between these entities and any external representation.

Thedescription is conceptual only, and does not specify any particular implementation. — end note ]8. Translated translation units and instantiation units are combined as follows: [ Note: Some or all ofthese may be supplied from a library. — end note ] Each translated translation unit is examined toproduce a list of required instantiations. [ Note: This may include instantiations which have beenexplicitly requested (14.7.2). — end note ] The definitions of the required templates are located.It is implementation-defined whether the source of the translation units containing these definitionsis required to be available.

[ Note: An implementation could encode sufficient information into thetranslated translation unit so as to ensure the source is not required here. — end note ] All the requiredinstantiations are performed to produce instantiation units. [ Note: These are similar to translatedtranslation units, but contain no references to uninstantiated templates and no template definitions.— end note ] The program is ill-formed if any instantiation fails.9.

All external entity references are resolved. Library components are linked to satisfy external referencesto entities not defined in the current translation. All such translator output is collected into a programimage which contains information needed for execution in its execution environment.2.31Character sets[lex.charset]The basic source character set consists of 96 characters: the space character, the control characters representing horizontal tab, vertical tab, form feed, and new-line, plus the following 91 graphical characters:14a b c d e f g h i j k l m n o p q r s t u v w x y zA B C D E F G H I J K L M N O P Q R S T U V W X Y Z0 1 2 3 4 5 6 7 8 9_ { } [ ] # ( ) < > % : ; . ? * + - / ^ & | ∼ ! = , \ " ’13) An implementation need not convert all non-corresponding source characters to the same execution character.14) The glyphs for the members of the basic source character set are intended to identify characters from the subset ofISO/IEC 10646 which corresponds to the ASCII character set.

However, because the mapping from source file characters to thesource character set (described in translation phase 1) is specified as implementation-defined, an implementation is required todocument how the basic source characters are represented in source files.§ 2.318© ISO/IEC 2011 – All rights reservedISO/IEC 14882:2011(E)2The universal-character-name construct provides a way to name other characters.hex-quad:hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digituniversal-character-name:\u hex-quad\U hex-quad hex-quadThe character designated by the universal-character-name \UNNNNNNNN is that character whose charactershort name in ISO/IEC 10646 is NNNNNNNN; the character designated by the universal-character-name \uNNNNis that character whose character short name in ISO/IEC 10646 is 0000NNNN.

If the hexadecimal value for auniversal-character-name corresponds to a surrogate code point (in the range 0xD800–0xDFFF, inclusive),the program is ill-formed. Additionally, if the hexadecimal value for a universal-character-name outside thec-char-sequence, s-char-sequence, or r-char-sequence of a character or string literal corresponds to a controlcharacter (in either of the ranges 0x00–0x1F or 0x7F–0x9F, both inclusive) or to a character in the basicsource character set, the program is ill-formed.153The basic execution character set and the basic execution wide-character set shall each contain all themembers of the basic source character set, plus control characters representing alert, backspace, and carriagereturn, plus a null character (respectively, null wide character), whose representation has all zero bits. Foreach basic execution character set, the values of the members shall be non-negative and distinct from oneanother.

In both the source and execution basic character sets, the value of each character after 0 in theabove list of decimal digits shall be one greater than the value of the previous. The execution character setand the execution wide-character set are implementation-defined supersets of the basic execution characterset and the basic execution wide-character set, respectively. The values of the members of the executioncharacter sets and the sets of additional members are locale-specific.2.41Trigraph sequences[lex.trigraph]Before any other processing takes place, each occurrence of one of the following sequences of three characters(“trigraph sequences”) is replaced by the single character indicated in Table 1.Table 1 — Trigraph sequencesTrigraph??=??/??’2Replacement#\ˆTrigraph??(??)??!Replacement[]|Trigraph??<??>??-Replacement{}∼[ Example:??=define arraycheck(a,b) a??(b??) ??!??! b??(a??)becomes#define arraycheck(a,b) a[b] || b[a]— end example ]3No other trigraph sequence exists.

Each ? that does not begin one of the trigraphs listed above is notchanged.15) A sequence of characters resembling a universal-character-name in an r-char-sequence (2.14.5) does not form a universalcharacter-name.§ 2.4© ISO/IEC 2011 – All rights reserved19ISO/IEC 14882:2011(E)2.5Preprocessing tokens[lex.pptoken]preprocessing-token:header-nameidentifierpp-numbercharacter-literaluser-defined-character-literalstring-literaluser-defined-string-literalpreprocessing-op-or-punceach non-white-space character that cannot be one of the above1Each preprocessing token that is converted to a token (2.7) shall have the lexical form of a keyword, anidentifier, a literal, an operator, or a punctuator.2A preprocessing token is the minimal lexical element of the language in translation phases 3 through 6.