gcc-2.96-69's iostream implementation fills with nulls instead of a real
character when a specific width is selected.  E.g.:

> cat bug22.c
#include <iostream>
int main(int, char**)
{
  std::cout << 0.5 << endl;
  std::cout.fill(' ');
  std::cout.width(6);
  std::cout << 0.5 << endl;
}
> g++ -v
Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/2.96/specs
gcc version 2.96 20000731 (Red Hat Linux 7.0)
> g++ bug22.c -o bug22
> ./bug22
0.5
^@^@^@0.5
>

Here I've rendered the nulls (0x00) the way Emacs does (^@), so that they
will survive email.  The same thing happens if the explicit setting of the
fill character is omitted; in either case GCC 2.95 produces a space and
2.96 produces nulls.  The behavior is particularly troublesome when the
output is then converted into a string using strstream, since the resulting
string will be empty due to the bogus nulls.