Development version of bash is very slow in running autoconf-generated scripts

[Stefano Lattarini]

Compared with Bash 4.2, the development version of bash is very slow
in running autoconf-generated configure scripts (or, to be more
precise, that's where I noticed the slowness; it might very well be
more generalized, but I haven't checked for that).

Some numbers:

  $ /bin/bash -c 'echo "$BASH_VERSION"'
  4.2.45(1)-release

  $ time CONFIG_SHELL=/bin/bash /bin/bash \
  >   ./configure CONFIG_SHELL=/bin/bash
  ...
  real  1m10.935s
  user  0m29.738s
  sys   0m12.669s


  $ $HOME/bleeding/bin/bash -c 'echo "$BASH_VERSION"'
  4.3.0(1)-alpha
  $ time CONFIG_SHELL=$HOME/bleeding/bin/bash $HOME/bleeding/bin/bash \
  >   ./configure CONFIG_SHELL=$HOME/bleeding/bin/bash
  ...
  real  4m45.671s
  user  4m22.744s
  sys   0m17.753s


Four times slower, yikes.  Any idea where these numbers might be coming
from?

Regards,
  Stefano