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Takashi Yano f79a46112e Cygwin: pipe: Use read pipe handle for select() on write pipe.
- Usually WriteQuotaAvailable retrieved by NtQueryInformationFile()
  on the write side reflects the space available in the inbound buffer
  on the read side. However, if a pipe read is currently pending,
  WriteQuotaAvailable on the write side is decremented by the number
  of bytes the read side is requesting. So it's possible (even likely)
  that WriteQuotaAvailable is 0, even if the inbound buffer on the
  read side is not full. This can lead to a deadlock situation:
  The reader is waiting for data, but select on the writer side
  assumes that no space is available in the read side inbound buffer.

  Currently, to avoid this stuation, read() does not request larger
  block than pipe size - 1. However, this mechanism does not take
  effect if the reader side is non-cygwin app.

  The only reliable information is available on the read side, so
  fetch info from the read side via the pipe-specific query handle
  (query_hdl) introduced.

  If the query_hdl (read handle) is kept in write side, writer can
  not detect closure of read pipe. Therefore, raw_write() counts
  write handle and query_hdl. If they are equal, only the pairs of
  write handle and query_hdl are alive. In this case, raw_write()
  returns EPIPE and raises SIGPIPE.

- Nonblocking pipes (PIPE_NOWAIT) are not well handled by non-Cygwin
  tools, so convert pipe handles to PIPE_WAIT handles when spawning
  a non-Cygwin process.
2021-09-14 13:01:40 +02:00
.github/workflows Cygwin: CI configuration update 2021-04-30 14:22:07 +01:00
config
etc
include Sync with upstream gcc. 2016-06-23 15:54:55 -04:00
libgloss libgloss/newlib: rename configure.in to configure.ac 2021-09-13 10:14:37 -04:00
newlib Regenerate Makefile.in after configure.in -> configure.ac change 2021-09-13 17:25:46 +02:00
texinfo
winsup Cygwin: pipe: Use read pipe handle for select() on write pipe. 2021-09-14 13:01:40 +02:00
.appveyor.yml Cygwin: Use parallel make on AppVeyor 2021-05-10 16:57:41 +01:00
.gitattributes
.gitignore Cygwin: drop all generated autotools files 2021-04-29 11:16:38 +02:00
COPYING
COPYING.LIB
COPYING.LIBGLOSS RISC-V: Add semihosting support 2020-12-16 16:40:34 -05:00
COPYING.NEWLIB RTEMS: Add <poll.h> and <sys/poll.h> 2021-01-05 13:41:34 -05:00
COPYING3
COPYING3.LIB
ChangeLog
MAINTAINERS
Makefile.def
Makefile.in
Makefile.tpl
README
README-maintainer-mode
compile
config-ml.in
config.guess Bump config.guess and config.sub 2021-02-24 11:03:28 +01:00
config.rpath
config.sub Bump config.guess and config.sub 2021-02-24 11:03:28 +01:00
configure
configure.ac
depcomp
djunpack.bat
install-sh
libtool.m4
ltgcc.m4
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ltversion.m4
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mkdep Use remove-advertising-clause script to edit BSD licenses 2020-01-29 19:03:31 +01:00
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README

		   README for GNU development tools

This directory contains various GNU compilers, assemblers, linkers, 
debuggers, etc., plus their support routines, definitions, and documentation.

If you are receiving this as part of a GDB release, see the file gdb/README.
If with a binutils release, see binutils/README;  if with a libg++ release,
see libg++/README, etc.  That'll give you info about this
package -- supported targets, how to use it, how to report bugs, etc.

It is now possible to automatically configure and build a variety of
tools with one command.  To build all of the tools contained herein,
run the ``configure'' script here, e.g.:

	./configure 
	make

To install them (by default in /usr/local/bin, /usr/local/lib, etc),
then do:
	make install

(If the configure script can't determine your type of computer, give it
the name as an argument, for instance ``./configure sun4''.  You can
use the script ``config.sub'' to test whether a name is recognized; if
it is, config.sub translates it to a triplet specifying CPU, vendor,
and OS.)

If you have more than one compiler on your system, it is often best to
explicitly set CC in the environment before running configure, and to
also set CC when running make.  For example (assuming sh/bash/ksh):

	CC=gcc ./configure
	make

A similar example using csh:

	setenv CC gcc
	./configure
	make

Much of the code and documentation enclosed is copyright by
the Free Software Foundation, Inc.  See the file COPYING or
COPYING.LIB in the various directories, for a description of the
GNU General Public License terms under which you can copy the files.

REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info
on where and how to report problems.