+AC_DEFUN([gl_PREREQ_FPENDING],
+[
+ AC_CACHE_CHECK(
+ [how to determine the number of pending output bytes on a stream],
+ ac_cv_sys_pending_output_n_bytes,
+ [
+ for ac_expr in \
+ \
+ '# glibc2' \
+ 'fp->_IO_write_ptr - fp->_IO_write_base' \
+ \
+ '# traditional Unix' \
+ 'fp->_ptr - fp->_base' \
+ \
+ '# BSD' \
+ 'fp->_p - fp->_bf._base' \
+ \
+ '# SCO, Unixware' \
+ '(fp->__ptr ? fp->__ptr - fp->__base : 0)' \
+ \
+ '# QNX' \
+ '(fp->_Mode & 0x2000 /*_MWRITE*/ ? fp->_Next - fp->_Buf : 0)' \
+ \
+ '# old glibc?' \
+ 'fp->__bufp - fp->__buffer' \
+ \
+ '# old glibc iostream?' \
+ 'fp->_pptr - fp->_pbase' \
+ \
+ '# emx+gcc' \
+ 'fp->_ptr - fp->_buffer' \
+ \
+ '# Minix' \
+ 'fp->_ptr - fp->_buf' \
+ \
+ '# Plan9' \
+ 'fp->wp - fp->buf' \
+ \
+ '# VMS' \
+ '(*fp)->_ptr - (*fp)->_base' \
+ \
+ '# e.g., DGUX R4.11; the info is not available' \
+ 1 \
+ ; do