相同的正则表达式，但在仅Linux和Windows上的结果不同C ++ [英] the same regex but different results on Linux and Windows only C++

问题描述

我的命令行程序具有以下模式：

有人知道为什么它变得贪婪吗？

谢谢。

解决方案

似乎有ab在5.4版中已修复的GCC中的ug。我的猜测是您在Windows设置上运行的是旧版本。

请在以下位置查看输出差异：

• 版本4.9 ： okey（错误）


• 版本5.4 ：否（正确）

是否包含 boost 似乎没有什么区别。

该错误与（?! \\1）有关，用<$ c代替$ c>（？！[/]）（在两种情况下）都可以解决此问题，但是显然，这会限制正则表达式与 / 仅分隔符：

• 带有（？！[1]） 的4.9版：否（正确）

此外，该Sim卡中出现了该错误请使用正则表达式：（。）（（?! \\1）。），该输入应拒绝类似 aa ：

• 版本5.4 ：否（右）


• 版本4.9 ： okey（错误）

结论：确保安装GCC 5.4或更高版本。

I have this pattern for my command-line program:
^s?([/|@#])(?:(?!\1).)+\1(?:(?!\1).)*\1(?:(?:gi?|ig)?(?:\1\d\d?)?|i)?$
based on ECMAScript 262 for C++.

This is a special pattern to check if the user have entered a correct command or not. It is a test against a string like this:
optional-s/one-or-more/anything/optional-g-or-i/optional-2-digits

Here is my previous question why I need this pattern.
Although it works fine on Linux, but does not work on Windows. Also I know about line-break on the two machines and I have read this: How are \n and \r handled differently on Linux and Windows?

My program does work with any files, it only gets the first argument of the command-line argv[ 1 ] and the std::regex_match tests if the entered-user-synopsis is correct or not.
Like: ./program 's/one/two/' *.txt that simply renames one to two for all txt files

the C++ code:

std::string argv_1 = argv[ 1 ]; // => s/one/two/
bool rename_is_correct =
std::regex_match( argv_1, std::basic_regex< char >
( "s?([/|@#])(?:(?!\\1).)+\\1(?:(?!\\1).)*\\1(?:(?:gi?|ig)?(?:\\1-?[1-9]\\d?)?|i)?" ) );

The Problem:
Although the pattern is non-greedy; on Windows it becomes greedy and matches more then 4 delimiters. Therefore it should not match /one/two/three/four/five/ but this string is matched!

---

NOTE:

• I deliberately have dropped ^ and $ assertions since in the C++ regex the std::regex_match by default has them and it no need to use them
• Also the two backslashes \\; one of them is escape character
• javescript code says no

const regex = /^s?([/|@#])(?:(?!\1).)+\1(?:(?!\1).)*\1((?:gi?|gi)\1-?[1-9]\d|i)?$/gm;
var str = 's/one/two/gi/-33/';
if( str.match( regex ) ){
  console.log( "okay" );
} else {
  console.log( "no" );
}

• Perl also says no, as you can see in the screenshot, but c++ says okay

Does someone know why it becomes greedy?

Thanks.

解决方案

There seems to have been a bug in GCC that got fixed in version 5.4. My guess is you are running an older version on your Windows set-up.

See the difference in output in:

• Version 4.9: "okey" (wrong)
• Version 5.4: "no" (right)

It does not seem to make a difference whether boost is included or not.

The bug is related to (?!\\1), as replacing it by (?![/]) (in both instances) solves the issue, but obviously that would limit the regular expression for use with the / delimiter only:

• Version 4.9 with (?![1]): "no" (correct)

Also, the bug appears with this simple regular expression: (.)((?!\\1).) which should reject an input like aa:

• Version 5.4: "no" (right)
• Version 4.9: "okey" (wrong)

Conclusion: make sure to install GCC version 5.4 or higher.

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