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

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

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.