ldexp() has a bug which cases the numeric coprocessor stack
to overflow if called several times. 
The bug can be traced down to src/libm/src/s_scalb.s:
It loads two operands, but leaves one of them on the stack:
  fild [esp+12]
  fldq [esp+4]
  fscale
  ret

Some other math functions use this routine and can crash under
quite rare circumstances.

Change djgpp/src/libm/src/s_scalbn.S to:

ENTRY(scalbn)
	fidl 12(%esp)
	fldl  4(%esp)
	fscale
	fxch  %st(1)
	fincstp
	ret


and rebuild libm.a