From: David Gibson <david@gibson.dropbear.id.au>
To: Kevin Locke <kevin@kevinlocke.name>
Cc: ccan@lists.ozlabs.org
Subject: Re: [PATCH 2/9] configurator: Reimplement run using popen
Date: Tue, 20 Sep 2016 23:28:26 +1000 [thread overview]
Message-ID: <20160920132826.GI20488@umbus> (raw)
In-Reply-To: <3c2cefdf-ea69-d3c4-dff6-bfdbbe63e8eb@kevinlocke.name>
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On Tue, Sep 20, 2016 at 12:22:41AM -0600, Kevin Locke wrote:
> On 09/19/2016 11:00 PM, David Gibson wrote:
> > On Sun, Sep 18, 2016 at 06:51:59PM -0600, Kevin Locke wrote:
> >> Rather than using fork+pipe+system+waitpid, most of which are only
> >> available on POSIX-like systems, use popen which is also available on
> >> Windows (under the name _popen).
> >
> > Concept looks good, one little wart.
> >
> >> [...]
> >>
> >> -static char *grab_fd(int fd)
> >> +static char *grab_stream(FILE *file)
> >> {
> >> - int ret;
> >> - size_t max, size = 0;
> >> + size_t max, ret, size = 0;
> >> char *buffer;
> >>
> >> - max = 16384;
> >> - buffer = malloc(max+1);
> >> - while ((ret = read(fd, buffer + size, max - size)) > 0) {
> >> + max = BUFSIZ;
> >> + buffer = malloc(max);
> >> + while ((ret = fread(buffer+size, 1, max - size, file)) == max - size) {
> >
> > This assumes that fread() will never return a short read except on EOF
> > or error. I expect that will be true in practice for regular files,
> > but I'm not sure if it's a good idea to rely on it.
>
> Interesting. I was under the impression that the fread couldn't short read.
> POSIX describes the return value as "the number of elements successfully
> read which is less than nitems only if a read error or end-of-file is
> encountered."[1] Now that I think about it, I suppose EINTR could be an
> issue for non-glibc systems. Is that what you had in mind, or are there
> other issues I'm overlooking? (Also for fwrite in 6/9?)
Ah..so it does. I'm afraid I just looked at the Linux man page, not
the POSIX requirements, and it didn't mention this constraint.
I guess it's ok then. Although.. I do wonder a bit whether we can
trust all implementations to actually comply with this requirement.
>
> Kevin
>
> 1. http://pubs.opengroup.org/onlinepubs/9699919799/functions/fread.html
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2016-09-20 14:21 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-19 0:51 [PATCH 0/9] configurator: Support for Windows and MSVC Kevin Locke
2016-09-19 0:51 ` [PATCH 1/9] configurator: Replace unlink with remove Kevin Locke
2016-09-20 4:50 ` David Gibson
2016-09-19 0:51 ` [PATCH 2/9] configurator: Reimplement run using popen Kevin Locke
2016-09-20 5:00 ` David Gibson
2016-09-20 6:22 ` Kevin Locke
2016-09-20 13:28 ` David Gibson [this message]
2016-09-19 0:52 ` [PATCH 3/9] configurator: Inline err.h functions from musl libc Kevin Locke
2016-09-20 5:03 ` David Gibson
2016-09-27 6:11 ` Rusty Russell
2016-09-19 0:52 ` [PATCH 4/9] configurator: Use native directory separator Kevin Locke
2016-09-20 5:04 ` David Gibson
2016-09-19 0:52 ` [PATCH 5/9] configurator: Mark non-Windows tests MAY_NOT_COMPILE Kevin Locke
2016-09-20 5:06 ` David Gibson
2016-09-19 0:52 ` [PATCH 6/9] configurator: Print test source without cat Kevin Locke
2016-09-20 5:09 ` David Gibson
2016-09-19 0:52 ` [PATCH 7/9] configurator: Fix compiler warning with compare Kevin Locke
2016-09-20 5:09 ` David Gibson
2016-09-19 0:52 ` [PATCH 8/9] configurator: Pass output cflag to configurator Kevin Locke
2016-09-20 5:23 ` David Gibson
2016-09-20 6:22 ` Kevin Locke
2016-09-20 13:32 ` David Gibson
2016-09-19 0:52 ` [PATCH 9/9] configurator: DEFAULT_{COMPILER, FLAGS} for MSVC Kevin Locke
2016-09-20 4:48 ` [PATCH 0/9] configurator: Support for Windows and MSVC David Gibson
2016-09-20 6:21 ` Kevin Locke
2016-09-20 12:25 ` David Gibson
2016-09-20 14:16 ` Daniel Burke
2016-09-22 2:00 ` David Gibson
2016-09-23 3:33 ` [PATCH v2 00/13] " Kevin Locke
2016-09-23 3:33 ` [PATCH v2 01/13] configurator: Replace unlink with remove Kevin Locke
2016-09-27 4:50 ` David Gibson
2016-09-23 3:33 ` [PATCH v2 02/13] configurator: Reimplement run using popen Kevin Locke
2016-09-27 4:52 ` David Gibson
2016-09-28 5:29 ` [PATCH v3 2/13] " Kevin Locke
2016-09-23 3:33 ` [PATCH v2 03/13] configurator: Inline err.h functions from musl libc Kevin Locke
2016-09-27 5:01 ` David Gibson
2016-09-28 5:35 ` [PATCH v3 3/13] configurator: Inline err.h functions Kevin Locke
2016-09-23 3:33 ` [PATCH v2 04/13] configurator: Use native directory separator Kevin Locke
2016-09-27 5:05 ` David Gibson
2016-09-23 3:33 ` [PATCH v2 05/13] configurator: Mark non-Windows tests MAY_NOT_COMPILE Kevin Locke
2016-09-27 5:05 ` David Gibson
2016-09-23 3:33 ` [PATCH v2 06/13] configurator: Print test source without cat Kevin Locke
2016-09-27 5:06 ` David Gibson
2016-09-28 5:38 ` Kevin Locke
2016-09-23 3:33 ` [PATCH v2 07/13] configurator: Fix compiler warning with compare Kevin Locke
2016-09-27 5:09 ` David Gibson
2016-09-23 3:33 ` [PATCH v2 08/13] configurator: Add output cflag option and macro Kevin Locke
2016-09-27 5:17 ` David Gibson
2016-09-23 3:33 ` [PATCH v2 09/13] configurator: DEFAULT_{COMPILER, FLAGS} for MSVC Kevin Locke
2016-09-27 5:17 ` David Gibson
2016-09-23 3:33 ` [PATCH v2 10/13] configurator: Fix warning in HAVE_FOR_LOOP_DECLARATION Kevin Locke
2016-09-27 5:10 ` David Gibson
2016-09-23 3:33 ` [PATCH v2 11/13] configurator: Return pointer difference as ptrdiff_t Kevin Locke
2016-09-27 5:10 ` David Gibson
2016-09-23 3:33 ` [PATCH v2 12/13] Makefile: Define CFLAGS_FORCE_C_SOURCE macro Kevin Locke
2016-09-27 5:18 ` David Gibson
2016-09-27 6:18 ` Rusty Russell
2016-09-28 2:01 ` David Gibson
2016-10-26 2:49 ` Rusty Russell
2016-09-23 3:33 ` [PATCH v2 13/13] Add appveyor.yml Kevin Locke
2016-09-27 5:20 ` David Gibson
2016-09-28 6:01 ` [PATCH v3 " Kevin Locke
2016-09-27 5:23 ` [PATCH v2 00/13] configurator: Support for Windows and MSVC David Gibson
2016-09-27 6:20 ` Rusty Russell
2016-09-28 6:32 ` Kevin Locke
2016-09-28 6:28 ` Kevin Locke
2016-09-29 0:21 ` David Gibson
2016-09-29 0:44 ` [PATCH v3 0/7] " Kevin Locke
2016-09-29 0:44 ` [PATCH v3 1/7] configurator: Reimplement run using popen Kevin Locke
2016-09-29 0:44 ` [PATCH v3 2/7] configurator: Inline err.h functions Kevin Locke
2016-09-29 0:44 ` [PATCH v3 3/7] configurator: Print test source without cat Kevin Locke
2016-09-29 0:44 ` [PATCH v3 4/7] configurator: Add output cflag option and macro Kevin Locke
2016-09-29 0:44 ` [PATCH v3 5/7] configurator: DEFAULT_{COMPILER, FLAGS} for MSVC Kevin Locke
2016-09-29 0:44 ` [PATCH v3 6/7] Makefile: Define CFLAGS_FORCE_C_SOURCE macro Kevin Locke
2016-09-29 0:44 ` [PATCH v3 7/7] Add appveyor.yml Kevin Locke
2016-09-30 15:08 ` [PATCH v3 0/7] configurator: Support for Windows and MSVC David Gibson
2016-10-03 3:14 ` Kevin Locke
2016-12-02 20:23 ` AppVeyor custom Git URL support (was Re: [PATCH v3 0/7] configurator: Support for Windows and MSVC) Kevin Locke
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