Re: [PATCH] 21_strings/basic_string/capacity/wchar_t/18654.cc

[Jonathan Wakely <jwakely dot gcc at gmail dot com>]

On 14 November 2015 at 00:56, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 13 November 2015 at 23:53, David Edelsohn <dje.gcc@gmail.com> wrote:
>> On Fri, Nov 13, 2015 at 1:40 PM, David Edelsohn <dje.gcc@gmail.com> wrote:
>>> http://www.cplusplus.com/reference/string/basic_string/reserve/
>>>
>>> "Note that the resulting string capacity may be equal or greater than n."
>>>
>>> The current testcase verifies that the capacity is exactly equal to
>>> the length of the string or reserve value, but the standard allows the
>>> capacity to be larger.  On AIX, the capacity is larger and the
>>> testcase incorrectly fails.
>>>
>>> Linux x86-64:
>>> i: 4
>>> str.length: 4
>>> str.capacity: 4
>>> str.capacity: 12
>>> str.capacity: 8
>>> str.capacity: 4
>>>
>>> AIX:
>>> i: 4
>>> str.length: 4
>>> str.capacity: 7   <-- i
>>> str.capacity: 14  <-- i*3
>>> str.capacity: 8   <-- i*2
>>> str.capacity: 7   <-- default
>>>
>>> * 21_strings/basic_string/capacity/wchar_t/18654.cc: Verify the
>>
>> Jonathan,
>>
>> AIX has 2-byte wchar_t in 32 bit mode, which seems to be the cause of
>> all of the libstdc++ testsuite wchar_t failures.  If GCC libstdc++ is
>> suppose to shrink-to-fit, how should the testcases be fixed?
>
> It's shrink-to-fit, but not below a minimum size, which depends on
> sizeof(wchar_t).
>
> Something like https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=63f5425911daddb9a328565cb0acc3b0f30144fa#patch81
> would work for both old and new string ABIs, I'll prepare an
> equivalent patch for the wchar_t test case.

This makes it adapt to the short-string buffer size, rather than
making an assumption about sizeof(wchar_t). Committed to trunk.

I'll have a look at the other wchar_t failures on AIX.

Attachment: patch.txt
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