How to check boost regex pattern is safe?

D.D.K-2637 966

Hi,
I'm using following code to split this wstring:

std::wstring inputString{L"#Err | NUM | ABC..."};
boost::algorithm::split_regex(parts, inputString, boost::wregex(L"|"));

This code runs without returning results.

I can't end this loop.

Is there a way to check or stop them in case the user put the wrong pattern?

Igor Tandetnik 1,116 Reputation points

2021-08-31T21:44:42.337+00:00

| has a special meaning in a regular expression; it's an "or" operator. Your regular expression means "empty string or empty string",

If you insist on using a regular expression, make it "\\|" . That is, escape the special character with a backslash.
D.D.K-2637 966 Reputation points

2021-08-31T22:44:49.66+00:00

Hi Igor,
Thank you for the explanation. i think in this case, the function should throw an exception or maybe return a result so i can continue working instead of freezing my screen.
Is there any way I can prevent this?
Viorel 122.5K Reputation points

2021-09-01T05:02:04.183+00:00

Many regex engines accept your pattern. It matches zero characters at any position of the input string. Since the length is zero, the algorithm cannot advance. It is probably an issue of split_regex: https://github.com/boostorg/regex/issues/76.

The equivalent splitters from some other languages do not exhibit such behaviour.

If the separator is entered by users, then maybe use boost::algorithm::split instead.
D.D.K-2637 966 Reputation points

2021-09-01T11:54:00.493+00:00

Hi Viorel,
Thanks for the suggestion, I'll break down the function now

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