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Re: [Patch] Let ordinary escaping in POSIX regex be valid

On 9/27/13 4:34 AM, Jonathan Wakely wrote:
On 27 September 2013 03:15, Tim Shen wrote:
POSIX ERE says that escaping an ordinary char, say R"\n" is not
permitted, because 'n' is not a special char. However, they also say
that : "Implementations are permitted to extend the language to allow
these. Conforming applications cannot use such constructs."

So let's support it not to make users surprised.

Booted and tested under -m32 and -m64
I'm wondering whether we want to have a stricter mode that doesn't
allow them, to help users avoid creating non-portable programs.  We
could check the value of the preprocessor macro __STRICT_ANSI__, which
is set by -std=c++11 but not by -std=gnu++11, although that's not
really the right flag. We want something more like the GNU shell
Indeed. I think that for now __STRICT_ANSI__ can do, it's important to manage to accept those otherwise, as we discovered yesterday, we easily reject quite a few rather sensible regex users can write or find in examples: this started when Tim, upon my suggestion, tried the examples in the new edition of Nicolai Josuttis book and found in one those an escaped closed curly bracket (note, closed, open are definitely fine), which apparently most of the other implementations do not reject.


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