CODEWITHSUNDEEP
c++regexwindows
Shakiba Moshiri
Shakiba Moshiri

Reputation: 23894

the same regex but different results on Linux and Windows only C++

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: 

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" );
}

enter image description here

Does someone know why it becomes greedy?

Thanks.

Upvotes: 2

Views: 2247

Answers (1)

trincot
trincot

Reputation: 350941

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:

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:

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

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

Upvotes: 3

Related Questions