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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/20/2022 1:20 PM, Enrico Forestieri wrote: > On Tue, Sep 20, 2022 at 06:18:54PM -0700, Ken Brown wrote: >> >> On 9/20/2022 2:54 AM, Enrico Forestieri wrote: >>> >>> I compared the behavior of read() and select() on 3 different platforms. >>> My conclusion is that, actually, read() behaves the same on all of them, >>> whereas cygwin differs in the way select() works. >> >> Then I'm even more confused than I was before. Are you saying that >> there are situations in which read() reports EOF but select() does not >> report read ready? Could you post the code you used for testing? > > I simply introduced a timeout for select() such that it returns on any > platform. On cygwin, when using "O_RDONLY | O_NONBLOCK" for the input > pipe, select() always returns 1, while on all other platforms it returns 0 > unless a client actually opens it for writing. > > As the "if (FD_ISSET(infd, &readfds))" block would not be entered on the > other platforms, I replaced it with "if (TRUE)" so that the read() is > always executed. In this conditions, the output is the same on all > platforms, meaning that the issue is the select() and not the read() call. > > This is the attached fifocomm-test.c file. I've just sent a patch to the cygwin-patches list that makes Cygwin behave the same as Linux. Thanks for reporting this problem. Ken P.S. I'm attaching a simplified test case that I used for testing the patch. --------------6lzJmlAZbo8ci2i7CQrhcGvj Content-Type: text/plain; charset=UTF-8; name="select_eof_fifo.c" Content-Disposition: attachment; filename="select_eof_fifo.c" Content-Transfer-Encoding: base64 I2luY2x1ZGUgPHN0ZGlvLmg+CiNpbmNsdWRlIDxzdGRsaWIuaD4KI2luY2x1ZGUgPHVuaXN0ZC5o PgojaW5jbHVkZSA8ZmNudGwuaD4KI2luY2x1ZGUgPHN5cy9zZWxlY3QuaD4KI2luY2x1ZGUgPGVy cm5vLmg+CiNpbmNsdWRlIDxzeXMvc3RhdC5oPgoKI2RlZmluZSBGSUZPX1BBVEggIi90bXAvbXlm aWZvIgoKaW50Cm1haW4gKCkKewogIGludCBmZCwgdG1wZmQsIG5zZWw7CiAgZmRfc2V0IHJlYWRm ZHM7CiAgc3RydWN0IHRpbWV2YWwgd2FpdF90bSA9IHsgMGwsIDIwMDAwMGwgfTsgLyogMjAwIG1p bGxpc2VjcyAqLwoKICBpZiAodW5saW5rIChGSUZPX1BBVEgpIDwgMCAgJiYgZXJybm8gIT0gRU5P RU5UKQogICAgewogICAgICBwZXJyb3IgKCJ1bmxpbmsiKTsKICAgICAgZXhpdCAoMSk7CiAgICB9 CgogIGlmIChta2ZpZm8gKEZJRk9fUEFUSCwgU19JUlVTUiB8IFNfSVdVU1IgfCBTX0lSR1JQIHwg U19JV0dSUCB8IFNfSVJPVEgKCSAgICAgIHwgU19JV09USCkgPCAwKQogICAgewogICAgICBwZXJy b3IgKCJta2ZpZm8iKTsKICAgICAgZXhpdCAoMSk7CiAgICB9CgogIHByaW50ZiAoIk9wZW5pbmcg YSBGSUZPIGZvciByZWFkaW5nIHdpdGggT19OT05CTE9DS1xuIik7CiAgaWYgKChmZCA9IG9wZW4g KEZJRk9fUEFUSCwgT19SRE9OTFkgfCBPX05PTkJMT0NLKSkgPCAwKQogICAgewogICAgICBwZXJy b3IgKCJvcGVuIik7CiAgICAgIGV4aXQgKDEpOwogICAgfQoKICBwcmludGYgKCJUZXN0aW5nIGZv ciByZWFkIHJlYWR5Li4uXG4iKTsKICBGRF9aRVJPICgmcmVhZGZkcyk7CiAgRkRfU0VUIChmZCwg JnJlYWRmZHMpOwogIG5zZWwgPSBzZWxlY3QgKGZkICsgMSwgJnJlYWRmZHMsIE5VTEwsIE5VTEws ICZ3YWl0X3RtKTsKICBwcmludGYgKCIgIHNlbGVjdCByZXR1cm5lZCAlZFxuIiwgbnNlbCk7Cgog IHByaW50ZiAoIk9wZW5pbmcgYW5kIGNsb3NpbmcgRklGTyBmb3Igd3JpdGluZy4uLlxuIik7CiAg aWYgKCh0bXBmZCA9IG9wZW4gKEZJRk9fUEFUSCwgT19XUk9OTFkpKSA8IDApCiAgICB7CiAgICAg IHBlcnJvciAoIm9wZW4iKTsKICAgICAgZXhpdCAoMSk7CiAgICB9CiAgaWYgKGNsb3NlICh0bXBm ZCkgPCAwKQogICAgewogICAgICBwZXJyb3IgKCJjbG9zZSIpOwogICAgICBleGl0ICgxKTsKICAg IH0KCiAgRkRfWkVSTyAoJnJlYWRmZHMpOwogIEZEX1NFVCAoZmQsICZyZWFkZmRzKTsKICBuc2Vs ID0gc2VsZWN0IChmZCArIDEsICZyZWFkZmRzLCBOVUxMLCBOVUxMLCAmd2FpdF90bSk7CiAgcHJp bnRmICgiICBub3cgc2VsZWN0IHJldHVybmVkICVkXG4iLCBuc2VsKTsKfQo= --------------6lzJmlAZbo8ci2i7CQrhcGvj--