Pre-DR: scanf %%
================

Should the scanf %% format skip whitespace before a % character in the
input?  For example, what should

#include <stdio.h>

int main (void)
{
  int dummy;
  return sscanf ("foo \t %bar1", "foo%%bar%d", &dummy);
}

return?  The standard seems clear (7.19.6.2#8) that it should return 1
- that %% acts differently from single ordinary characters in the
format string - but implementations differ on this, some returning 1
and some returning 0.

I'm not sure there's a defect here and I suspect a change would be
considered bad for compatibility (and you can still match a single %
character with %1[%]), but whether it was intended for %% to eat
whitespace could do with clarification.