这是 C++11 正则表达式错误我还是编译器?

问题描述

好的，这不是我遇到这个问题的原始程序，但我将它复制到一个更小的程序中.很简单的问题.

main.cpp:

#include #include <正则表达式>使用命名空间标准；int main(){正则表达式 r1("S");printf("S 有效.
");正则表达式 r2(".");printf(".有效.
");正则表达式 r3(".+");printf(".+ 有效.
");正则表达式 r4("[0-9]");printf("[0-9] 有效.
");返回0；}

用这个命令编译成功，没有错误提示:

$ g++ -std=c++0x main.cpp

顺便说一下，g++ -v 的最后一行是:

gcc 版本 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3)

当我尝试运行它时的结果:

$ ./a.outS作品..作品..+ 作品.抛出std::regex_error"实例后调用终止what(): regex_error中止

如果我将 r4 更改为 \s、\w 或 [a-z]，也会发生同样的情况.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.是否已在 4.6.2 中修复?

Joachim Pileborg 提供了一个部分解决方案，使用额外的 regex_constants 参数来启用支持方括号的语法，但既没有 basic，extended、awk 和 ECMAScript 似乎都支持反斜杠转义的术语，例如 \s、\w，或 \t.

编辑 2:

使用原始字符串(R"(w)" 而不是 "\w")似乎也不起作用.

更新: 现已在 GCC 4.9.0 中实现和发布

根据 C++11 标准 (28.8.2) basic_regex() 默认使用 regex_constants::ECMAScript 标志，因此它必须理解此语法.><块引用>

这个 C++11 正则表达式错误是我还是编译器?

gcc-4.6.1 不支持 c++11 正则表达式 (28.13).

OK, this isn't the original program I had this problem in, but I duplicated it in a much smaller one. Very simple problem.

main.cpp:

#include <iostream>
#include <regex>
using namespace std;

int main()
{
    regex r1("S");
    printf("S works.
");
    regex r2(".");
    printf(". works.
");
    regex r3(".+");
    printf(".+ works.
");
    regex r4("[0-9]");
    printf("[0-9] works.
");
    return 0;
}

Compiled successfully with this command, no error messages:

$ g++ -std=c++0x main.cpp

The last line of g++ -v, by the way, is:

gcc version 4.6.1 (Ubuntu/Linaro 4.6.1-9ubuntu3)

And the result when I try to run it:

$ ./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?

EDIT:

Joachim Pileborg has supplied a partial solution, using an extra regex_constants parameter to enable a syntax that supports square brackets, but neither basic, extended, awk, nor ECMAScript seem to support backslash-escaped terms like \s, \w, or \t.

EDIT 2:

Using raw strings (R"(w)" instead of "\w") doesn't seem to work either.

Update: <regex> is now implemented and released in GCC 4.9.0

^{Old answer:}

ECMAScript syntax accepts [0-9], s, w, etc, see ECMA-262 (15.10). Here's an example with boost::regex that also uses the ECMAScript syntax by default:

#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:

$ g++ -std=c++0x *.cc -lboost_regex && ./a.out 1

According to the C++11 standard (28.8.2) basic_regex() uses regex_constants::ECMAScript flag by default so it must understand this syntax.

Is this C++11 regex error me or the compiler?

gcc-4.6.1 doesn't support c++11 regular expressions (28.13).

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