From: Harald van Dijk <harald@gigawatt.nl>
To: Roy <roytam@gmail.com>
Cc: dash@vger.kernel.org
Subject: Re: [PATCH] printf: use %ll instead of %j
Date: Mon, 03 Dec 2012 18:58:17 +0100 [thread overview]
Message-ID: <50BCE839.1060606@gigawatt.nl> (raw)
In-Reply-To: <50BCDA80.8000705@gigawatt.nl>
[-- Attachment #1: Type: text/plain, Size: 1773 bytes --]
On 12/03/2012 05:59 PM, Harald van Dijk wrote:
> On 12/03/2012 08:42 AM, Roy wrote:
>> MSYS libc does not support %j[dXx] format, only %ll[dXx] is supported.
>>
>> diff --git a/src/bltin/printf.c b/src/bltin/printf.c
>> index 893295c..12ce660 100644
>> --- a/src/bltin/printf.c
>> +++ b/src/bltin/printf.c
>> @@ -319,11 +319,12 @@ mklong(const char *str, const char *ch)
>> char *copy;
>> size_t len;
>>
>> - len = ch - str + 3;
>> + len = ch - str + 4;
>> STARTSTACKSTR(copy);
>> copy = makestrspace(len, copy);
>> - memcpy(copy, str, len - 3);
>> - copy[len - 3] = 'j';
>> + memcpy(copy, str, len - 4);
>> + copy[len - 4] = 'l';
>> + copy[len - 3] = 'l';
>> copy[len - 2] = *ch;
>> copy[len - 1] = '\0';
>> return (copy);
>
> The calling code uses the result to print intmax_t and uintmax_t values.
> Printing intmax_t values with %lld is wrong, this will only work if
> intmax_t is really a typedef for long long (which may be true on your
> system, but is not required by the standard).
>
> The other patch that Jonathan linked to should work just fine.
Here's a slightly tweaked version of that patch. Regardless of whether
PRIdMAX is defined as "jd" or as "lld", the use of memcpy here, first
copying "jd"/"lld" and the null byte, and only changing the 'd' after
that, surprisingly results in slightly shorter object code than the
original byte-by-byte approach, even though memcpy is fully inlined.
Perhaps that could be a reason for applying this, even if the original
reason for it, making the code work on not-quite-conforming systems,
isn't good enough to get it in dash.
Tested with normal glibc, and with glibc hacked to not provide PRIdMAX.
Cheers,
Harald
[-- Attachment #2: printf-PRIdMAX.patch --]
[-- Type: text/x-patch, Size: 875 bytes --]
diff --git a/src/bltin/printf.c b/src/bltin/printf.c
index 893295c..5f9e81c 100644
--- a/src/bltin/printf.c
+++ b/src/bltin/printf.c
@@ -316,16 +316,24 @@ out:
static char *
mklong(const char *str, const char *ch)
{
+ /*
+ * Replace a string like "%92.3u" with "%92.3"PRIuMAX.
+ *
+ * Although C99 does not guarantee it, we assume PRIiMAX,
+ * PRIoMAX, PRIuMAX, PRIxMAX, and PRIXMAX are all the same
+ * as PRIdMAX with the final 'd' replaced by the corresponding
+ * character.
+ */
+
char *copy;
size_t len;
- len = ch - str + 3;
+ len = ch - str + sizeof(PRIdMAX);
STARTSTACKSTR(copy);
copy = makestrspace(len, copy);
- memcpy(copy, str, len - 3);
- copy[len - 3] = 'j';
+ memcpy(copy, str, len - sizeof(PRIdMAX));
+ memcpy(copy + len - sizeof(PRIdMAX), PRIdMAX, sizeof(PRIdMAX));
copy[len - 2] = *ch;
- copy[len - 1] = '\0';
return (copy);
}
next prev parent reply other threads:[~2012-12-03 17:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-03 7:42 [PATCH] printf: use %ll instead of %j Roy
2012-12-03 14:32 ` Jonathan Nieder
[not found] ` <50BCDA80.8000705@gigawatt.nl>
2012-12-03 17:58 ` Harald van Dijk [this message]
2012-12-04 6:38 ` Jonathan Nieder
2013-08-23 10:30 ` Herbert Xu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=50BCE839.1060606@gigawatt.nl \
--to=harald@gigawatt.nl \
--cc=dash@vger.kernel.org \
--cc=roytam@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).