This is the mail archive of the
libstdc++@gcc.gnu.org
mailing list for the libstdc++ project.
Re: [v3] basic_string::reserve() shrink-to-fit?
Nathan Myers wrote:
On Thu, Dec 11, 2003 at 03:51:36PM +0100, Neil Ferguson wrote:
Initial capacity: 0
After 6 char assign: 6
After reserve(1000000): 1003491
After reserve(): 1003491
ie. reserve() doesn't seem to shrink the string capacity to fit.
I'm afraid that's what's supposed to happen, in basic_string<> and
in vector<>. The idiom for shrinking to fit is to use swap().
Minimally,
std::swap(std::string(str.data(), str.size()), str);
This might be a good thing to put in the FAQ.
When this was raised as a Defect Report, the committee recognized
it as clunky, but not, technically, a Defect, and thus beyond their
charter to change at that time. For the next standard they have
more latitude.
Nathan Myers
ncm-nospam@cantrip.org
Could you give me a reference to read, please? My understanding is
that vectors should not shrink via resize(), but that strings can.
I just rechecked my copy of ISO 14882 (admittedly a 1998-09-01 one)
and section 21.3.3, paragraph 11 (on page 391) says that shrinking
and shrinking to fit are permitted for strings, but implementations
are not bound to comply with a request to do so.
Neil.