[PATCH] improve string find algorithm

[Jonathan Wakely]

On 06/01/17 20:32 +0000, Jonathan Wakely wrote:
>On 06/01/17 13:35 +0000, Jonathan Wakely wrote:
>>I'm surprised we don't have any tests for this case, but apparently we
>>don't, as your patch passes all our tests.
>
>My bad, we do have tests that FAIL with this patch, but only after a
>'make clean' (otherwise the explicit instantiation definitions in the
>library don't get rebuilt after applying the patch, so the tests use
>the old code).
>
>FAIL: 21_strings/basic_string/operations/find/char/1.cc execution test
>FAIL: 21_strings/basic_string/operations/find/wchar_t/1.cc execution test
>
>These fail on assert(s.find(s, 1) == std::string::npos) which gives
>the wrong answer as explained in my previous mail.
>
>The infinite loop caused by this patch isn't caught by any existing
>tests, so I'll add a check for that.

Committed to trunk.

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