这是 C++11 正则表达式错误我还是编译器？
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Is this C++11 regex error me or the compiler?
提问by Shay Guy
OK, this isn't the original program I had this problem in, but I duplicated it in a much smaller one. Very simple problem.
好的，这不是我遇到此问题的原始程序，但我将其复制到一个小得多的程序中。很简单的问题。
main.cpp:
主.cpp：
#include <iostream>
#include <regex>
using namespace std;
int main()
{
regex r1("S");
printf("S works.\n");
regex r2(".");
printf(". works.\n");
regex r3(".+");
printf(".+ works.\n");
regex r4("[0-9]");
printf("[0-9] works.\n");
return 0;
}
Compiled successfully with this command, no error messages:
用这个命令编译成功，没有错误信息：
$ g++ -std=c++0x main.cpp
The last line of g++ -v, by the way, is:
g++ -v顺便说一下，最后一行是：
gcc version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3)
And the result when I try to run it:
当我尝试运行它时的结果：
$ ./a.out
S works.
. works.
.+ works.
terminate called after throwing an instance of 'std::regex_error'
what(): regex_error
Aborted
It happens the same way if I change r4 to \\s, \\w, or [a-z]. Is this a problem with the compiler? I might be able to believe that C++11's regex engine has different ways of saying "whitespace" or "word character," but square brackets not working is a stretch. Is it something that's been fixed in 4.6.2?
如果我将 r4 更改为\\s, \\w, 或，也会发生同样的情况[a-z]。这是编译器的问题吗？我可能会相信 C++11 的正则表达式引擎有不同的说法“空白”或“单词字符”，但方括号不起作用是一种延伸。它是否已在 4.6.2 中修复？
EDIT:
编辑：
Joachim Pileborg has supplied a partial solution, using an extra regex_constantsparameter to enable a syntax that supports square brackets, but neither basic, extended, awk, nor ECMAScriptseem to support backslash-escaped terms like \\s, \\w, or \\t.
约阿希姆Pileborg已提供的部分解决方案，使用额外的regex_constants参数，以使得语法可支持方括号，但既不basic，extended，awk，也不ECMAScript似乎支持反斜杠转义术语如\\s，\\w，或\\t。
EDIT 2:
编辑2：
Using raw strings (R"(\w)"instead of "\\w") doesn't seem to work either.
使用原始字符串（R"(\w)"而不是"\\w"）似乎也不起作用。
采纳答案by jfs
Update: <regex>is now implemented and released in GCC 4.9.0
更新：<regex>现在在 GCC 4.9.0 中实现和发布
Old answer:
旧答案：
ECMAScript syntax accepts [0-9], \s, \w, etc, see ECMA-262 (15.10). Here's an example with boost::regexthat also uses the ECMAScript syntax by default:
ECMAScript 语法接受[0-9]、\s、\w等，请参阅ECMA-262 (15.10)。这是一个boost::regex默认情况下也使用 ECMAScript 语法的示例：
#include <boost/regex.hpp>
int main(int argc, char* argv[]) {
using namespace boost;
regex e("[0-9]");
return argc > 1 ? !regex_match(argv[1], e) : 2;
}
It works:
有用：
$ g++ -std=c++0x *.cc -lboost_regex && ./a.out 1
According to the C++11 standard (28.8.2) basic_regex()uses regex_constants::ECMAScriptflag by default so it must understand this syntax.
根据 C++11 标准 (28.8.2)默认basic_regex()使用regex_constants::ECMAScript标志，因此它必须理解此语法。
Is this C++11 regex error me or the compiler?
这是 C++11 正则表达式错误我还是编译器？
gcc-4.6.1 doesn't support c++11 regular expressions (28.13).
回答by Some programmer dude
The error is because creating a regex by default uses ECMAScript syntax for the expression, which doesn't support brackets. You should declare the expression with the basicor extendedflag:
错误是因为默认情况下创建正则表达式使用 ECMAScript 语法作为表达式，它不支持括号。您应该使用basicorextended标志声明表达式：
std::regex r4("[0-9]", std::regex_constants::basic);
EditSeems like libstdc++ (part of GCC, and the library that handles all C++ stuff) doesn't fully implement regular expressions yet. In their status documentthey say that Modified ECMAScript regular expression grammaris not implemented yet.
编辑似乎 libstdc++（GCC 的一部分，以及处理所有 C++ 内容的库）还没有完全实现正则表达式。在他们的状态文档中，他们说Modified ECMAScript 正则表达式语法尚未实现。
回答by Drew Noakes
Regex support improved between gcc 4.8.2 and 4.9.2. For example, the regex =[A-Z]{3}was failing for me with:
在 gcc 4.8.2 和 4.9.2 之间改进了正则表达式支持。例如，正则表达式=[A-Z]{3}对我来说失败了：
Regex error
正则表达式错误
After upgrading to gcc 4.9.2, it works as expected.
升级到 gcc 4.9.2 后，它按预期工作。
