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From: Stefan Beller <sbeller@google.com>
To: "Torsten Bögershausen" <tboegi@web.de>
Cc: Paul Tan <pyokagan@gmail.com>,
	"git@vger.kernel.org" <git@vger.kernel.org>,
	Johannes Schindelin <johannes.schindelin@gmx.de>
Subject: Re: [PATCH v4 01/44] wrapper: implement xopen()
Date: Sun, 28 Jun 2015 22:04:02 -0700	[thread overview]
Message-ID: <CAGZ79kYYGpB6wGO6r67P0NLP9fda_UjZtLfwqmrWZrCKOYqZWQ@mail.gmail.com> (raw)
In-Reply-To: <5590CE10.3020104@web.de>

On Sun, Jun 28, 2015 at 9:48 PM, Torsten Bögershausen <tboegi@web.de> wrote:
> On 06/28/2015 04:05 PM, Paul Tan wrote:
>>
>> A common usage pattern of open() is to check if it was successful, and
>> die() if it was not:
>>
>>         int fd = open(path, O_WRONLY | O_CREAT, 0777);
>>         if (fd < 0)
>>                 die_errno(_("Could not open '%s' for writing."), path);
>>
>> Implement a wrapper function xopen() that does the above so that we can
>> save a few lines of code, and make the die() messages consistent.
>>
>> Helped-by: Torsten Bögershausen <tboegi@web.de>
>> Helped-by: Jeff King <peff@peff.net>
>> Signed-off-by: Paul Tan <pyokagan@gmail.com>
>> ---
>>   git-compat-util.h |  1 +
>>   wrapper.c         | 25 +++++++++++++++++++++++++
>>   2 files changed, 26 insertions(+)
>>
>> diff --git a/git-compat-util.h b/git-compat-util.h
>> index c6d391f..e168dfd 100644
>> --- a/git-compat-util.h
>> +++ b/git-compat-util.h
>> @@ -717,6 +717,7 @@ extern void *xrealloc(void *ptr, size_t size);
>>   extern void *xcalloc(size_t nmemb, size_t size);
>>   extern void *xmmap(void *start, size_t length, int prot, int flags, int
>> fd, off_t offset);
>>   extern void *xmmap_gently(void *start, size_t length, int prot, int
>> flags, int fd, off_t offset);
>> +extern int xopen(const char *path, int flags, ...);
>>   extern ssize_t xread(int fd, void *buf, size_t len);
>>   extern ssize_t xwrite(int fd, const void *buf, size_t len);
>>   extern ssize_t xpread(int fd, void *buf, size_t len, off_t offset);
>> diff --git a/wrapper.c b/wrapper.c
>> index ff49807..7e13ae0 100644
>> --- a/wrapper.c
>> +++ b/wrapper.c
>> @@ -189,6 +189,31 @@ void *xcalloc(size_t nmemb, size_t size)
>>   # endif
>>   #endif
>>   +/**
>> + * xopen() is the same as open(), but it die()s if the open() fails.
>> + */
>> +int xopen(const char *path, int oflag, ...)
>> +{
>> +       mode_t mode = 0;
>> +       va_list ap;
>> +
>> +       va_start(ap, oflag);
>> +       if (oflag & O_CREAT)
>> +               mode = va_arg(ap, mode_t);
>> +       va_end(ap);
>> +
>> +       assert(path);
>> +
>
> 2 remarks:
> - I don't know if and why we need the assert() here (but don't know if we
> have a strategie in Git for assert())

Yeah I think we usually do

    if (!assertion)
        die("BUG: assertion not met");

> - Having xopen() with 2 or 3 parameter is good, but the current may need
> some tweaks for better portability:
>
> int xopen(const char *path, int oflag, ...)
> {
>         mode_t mode = 0;
>         if (oflag & O_CREAT) {
>                 va_list ap;
>                 va_start(ap, oflag);
>                 mode = va_arg(ap, int);
>                 va_end(ap);
>
>             }
>
> See e.g.
> <http://blitiri.com.ar/git/r/libfiu/c/37f6a98110e3bb59bbb4971241baa3a385c3f724/>
> why va_arg(ap, int) should be used:
>
>
> +
> +               /* va_arg() can only take fully promoted types, and mode_t
> +                * sometimes is smaller than an int, so we should always
> pass
> +                * int to it, and not mode_t. Not doing so would may result
> in
> +                * a compile-time warning and run-time error. We asume that
> it
> +                * is never bigger than an int, which holds in practise. */
> +               mode = va_arg(l, int);
> +
>
>

  reply	other threads:[~2015-06-29  5:04 UTC|newest]

Thread overview: 74+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-06-28 14:05 [PATCH v4 00/44] Make git-am a builtin Paul Tan
2015-06-28 14:05 ` [PATCH v4 01/44] wrapper: implement xopen() Paul Tan
2015-06-29  4:48   ` Torsten Bögershausen
2015-06-29  5:04     ` Stefan Beller [this message]
2015-06-29 17:18     ` Junio C Hamano
2015-07-01  6:05       ` Paul Tan
2015-07-01  6:04     ` Paul Tan
2015-06-28 14:05 ` [PATCH v4 02/44] wrapper: implement xfopen() Paul Tan
2015-06-28 14:05 ` [PATCH v4 03/44] builtin-am: implement skeletal builtin am Paul Tan
2015-06-28 14:05 ` [PATCH v4 04/44] builtin-am: implement patch queue mechanism Paul Tan
2015-06-29  5:08   ` Stefan Beller
2015-07-07 12:50     ` Paul Tan
2015-06-28 14:05 ` [PATCH v4 05/44] builtin-am: split out mbox/maildir patches with git-mailsplit Paul Tan
2015-06-28 14:05 ` [PATCH v4 06/44] builtin-am: auto-detect mbox patches Paul Tan
2015-06-28 14:05 ` [PATCH v4 07/44] builtin-am: extract patch and commit info with git-mailinfo Paul Tan
2015-06-28 14:05 ` [PATCH v4 08/44] builtin-am: apply patch with git-apply Paul Tan
2015-06-28 14:05 ` [PATCH v4 09/44] builtin-am: implement committing applied patch Paul Tan
2015-06-28 14:05 ` [PATCH v4 10/44] builtin-am: refuse to apply patches if index is dirty Paul Tan
2015-06-28 14:05 ` [PATCH v4 11/44] builtin-am: implement --resolved/--continue Paul Tan
2015-06-28 14:05 ` [PATCH v4 12/44] builtin-am: implement --skip Paul Tan
2015-06-28 14:05 ` [PATCH v4 13/44] builtin-am: implement --abort Paul Tan
2015-06-28 14:05 ` [PATCH v4 14/44] builtin-am: reject patches when there's a session in progress Paul Tan
2015-06-28 14:05 ` [PATCH v4 15/44] builtin-am: implement -q/--quiet, GIT_QUIET Paul Tan
2015-06-28 14:05 ` [PATCH v4 16/44] builtin-am: exit with user friendly message on failure Paul Tan
2015-06-28 14:05 ` [PATCH v4 17/44] builtin-am: implement -s/--signoff Paul Tan
2015-06-28 14:05 ` [PATCH v4 18/44] cache-tree: introduce write_index_as_tree() Paul Tan
2015-06-28 14:05 ` [PATCH v4 19/44] builtin-am: implement --3way, am.threeway Paul Tan
2015-06-30  0:18   ` Stefan Beller
2015-06-28 14:05 ` [PATCH v4 20/44] builtin-am: implement --rebasing mode Paul Tan
2015-06-28 14:05 ` [PATCH v4 21/44] builtin-am: bypass git-mailinfo when --rebasing Paul Tan
2015-06-28 14:05 ` [PATCH v4 22/44] builtin-am: handle stray state directory Paul Tan
2015-06-28 14:05 ` [PATCH v4 23/44] builtin-am: implement -u/--utf8 Paul Tan
2015-06-28 14:05 ` [PATCH v4 24/44] builtin-am: implement -k/--keep, --keep-non-patch Paul Tan
2015-06-28 14:05 ` [PATCH v4 25/44] builtin-am: implement --[no-]message-id, am.messageid Paul Tan
2015-06-28 14:05 ` [PATCH v4 26/44] builtin-am: support --keep-cr, am.keepcr Paul Tan
2015-06-28 14:05 ` [PATCH v4 27/44] builtin-am: implement --[no-]scissors Paul Tan
2015-07-07  8:23   ` Paul Tan
2015-06-28 14:05 ` [PATCH v4 28/44] builtin-am: pass git-apply's options to git-apply Paul Tan
2015-06-29 23:56   ` Stefan Beller
2015-07-01 10:22     ` Paul Tan
2015-07-01 17:01       ` Stefan Beller
2015-06-28 14:05 ` [PATCH v4 29/44] builtin-am: implement --ignore-date Paul Tan
2015-06-28 14:05 ` [PATCH v4 30/44] builtin-am: implement --committer-date-is-author-date Paul Tan
2015-06-28 14:05 ` [PATCH v4 31/44] builtin-am: implement -S/--gpg-sign, commit.gpgsign Paul Tan
2015-06-29 23:51   ` Stefan Beller
2015-07-01  8:01     ` Paul Tan
2015-07-01 16:43       ` Stefan Beller
2015-06-28 14:05 ` [PATCH v4 32/44] builtin-am: invoke post-rewrite hook Paul Tan
2015-06-28 14:05 ` [PATCH v4 33/44] builtin-am: support automatic notes copying Paul Tan
2015-06-28 14:05 ` [PATCH v4 34/44] builtin-am: invoke applypatch-msg hook Paul Tan
2015-06-28 14:05 ` [PATCH v4 35/44] builtin-am: invoke pre-applypatch hook Paul Tan
2015-06-28 14:05 ` [PATCH v4 36/44] builtin-am: invoke post-applypatch hook Paul Tan
2015-06-28 14:05 ` [PATCH v4 37/44] builtin-am: rerere support Paul Tan
2015-06-28 14:06 ` [PATCH v4 38/44] builtin-am: support and auto-detect StGit patches Paul Tan
2015-06-29 20:42   ` Stefan Beller
2015-06-29 20:51     ` Eric Sunshine
2015-06-29 21:39       ` Junio C Hamano
2015-07-01  7:25         ` Paul Tan
2015-06-28 14:06 ` [PATCH v4 39/44] builtin-am: support and auto-detect StGit series files Paul Tan
2015-06-28 14:06 ` [PATCH v4 40/44] builtin-am: support and auto-detect mercurial patches Paul Tan
2015-06-29 20:32   ` Stefan Beller
2015-06-29 20:32     ` Stefan Beller
2015-07-01  9:07       ` Paul Tan
2015-07-01  8:48     ` Paul Tan
2015-06-28 14:06 ` [PATCH v4 41/44] builtin-am: implement -i/--interactive Paul Tan
2015-06-28 14:06 ` [PATCH v4 42/44] builtin-am: implement legacy -b/--binary option Paul Tan
2015-06-29 20:05   ` Stefan Beller
     [not found]     ` <CABPQNSakaoyNRuNz=bcDYWdy4e2O3M4UuYoOT5JAV1mt-BiAOw@mail.gmail.com>
2015-07-14 10:09       ` Paul Tan
2015-06-28 14:06 ` [PATCH v4 43/44] builtin-am: check for valid committer ident Paul Tan
2015-06-29 20:02   ` Stefan Beller
2015-07-01  6:43     ` Paul Tan
2015-06-28 14:06 ` [PATCH v4 44/44] builtin-am: remove redirection to git-am.sh Paul Tan
2015-06-29  5:01 ` [PATCH v4 00/44] Make git-am a builtin Stefan Beller
2015-06-30  0:19   ` Stefan Beller

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