[Bug libstdc++/20114] New: Non-monotonic behavior of string::reserve

[kreckel at ginac dot de]

gromit:/tmp$ cat resize.cc
#include <iostream>
#include <string>
using namespace std;

int main()
{
    string line;
    for ( size_t c=8162; c<8166; ++c ) {
        line.reserve(c);
        cout << line.capacity() << endl;
    }
}
gromit:/tmp$ g++-3.4 -v
Lese Spezifikationen von /usr/lib/gcc/i486-linux/3.4.4/specs
Konfiguriert mit: ../src/configure -v
--enable-languages=c,c++,java,f77,pascal,objc,ada,treelang --prefix=/usr
--libexecdir=/usr/lib --with-gxx-include-dir=/usr/include/c++/3.4
--enable-shared --with-system-zlib --enable-nls --without-included-gettext
--program-suffix=-3.4 --enable-__cxa_atexit --enable-libstdcxx-allocator=mt
--enable-clocale=gnu --enable-libstdcxx-debug --enable-java-gc=boehm
--enable-java-awt=gtk --disable-werror i486-linux
Thread-Modell: posix
gcc-Version 3.4.4 20041218 (prerelease) (Debian 3.4.3-6)
gromit:/tmp$ g++-3.4 resize.cc
gromit:/tmp$ ./a.out
8163
8163
16355
12259

Apparently, reserve/resize overallocate when called with 8164 as argument
(unless the string has been empty before).  There are other such points, at
12260, 16356, 20452, 24548 and so on at each bump where a (monotonic) change in
size is intented.

-- 
           Summary: Non-monotonic behavior of string::reserve
           Product: gcc
           Version: 3.4.4
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kreckel at ginac dot de
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i486-linux
  GCC host triplet: i486-linux
GCC target triplet: i486-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20114