为什么在尾随反斜杠之前解析原始字符串文字？

Question

从Phases of translation开始，反斜杠连接下一行发生在阶段2，字符串文字评估发生在阶段3。那么为什么下面的代码之前进行字符串评估？

#include<string>
#include<iostream>

int main() {
    std::string s = R"(before\
after)";
    std::cout << s;
}

给出：

before\
after

而不是：

beforeafter

Phase 2

Whenever backslash appears at the end of a line (immediately followed by zero or more whitespace characters other than new-line followed by (since C++23) the newline character), these characters are deleted, combining two physical source lines into one logical source line. [...]

Phase 3

The source file is decomposed into comments, sequences of whitespace characters (space, horizontal tab, new-line, vertical tab, and form-feed), and preprocessing tokens, which are the following: a) header names such as or "myfile.h" b) identifiers c) preprocessing numbers d) character and string literals , including user-defined (since C++11) [...]

Answer 1

原始字符串文字 explicitly undo phases 1&2:

If the next character begins a sequence of characters that could be the prefix and initial double quote of a raw string literal, such as R", the next preprocessing token shall be a raw string literal. Between the initial and final double quote characters of the raw string, any transformations performed in phases 1 and 2 (universal-character-names and line splicing) are reverted; this reversion shall apply before any d-char, r-char, or delimiting parenthesis is identified.

为什么在尾随反斜杠之前解析原始字符串文字？

Why is raw string literal parsed before trailing backslash?

c++

backslash

string-literals

rawstring

c-preprocessor