Hi,
Brian Koropoff wrote:
> The printf builtin modifies the user's format strings
> by prefixing integer conversion specifications with the
> 'j' (intmax_t) length modifier. Since this is not portable,
> instead prefix them with the length modifier extracted from
> the PRIdMAX constant.
This assumes PRIdMAX, PRIxMAX, etc all consist of the same prefix
before the standard characters. Since the most common definitions
are j<usual char>, l<usual char>, q<usual char>, I64<usual char>,
and ll<usual char>, that's probably a safe assumption. I wonder why
C99 and its predecessors did not use
printf("%"PRIMAX"x\n", val);
Oh well. Maybe it would warrant a comment, though?
/*
* Replace a string like
*
* %92.3u
* ^ ^--- ch
* '-------- str
*
* 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.
*/
> --- a/src/bltin/printf.c
> +++ b/src/bltin/printf.c
> @@ -317,15 +317,16 @@ static char *
> mklong(const char *str, const char *ch)
> {
> char *copy;
> - size_t len;
> + size_t len;
> + size_t pridmax_len = strlen(PRIdMAX);
I think just using strlen(PRIdMAX) as-is would make it clearer that we
are expecting the compiler to inline the "strlen" and provides a
reminder of the value, too (i.e., is it 2 or 3 for "jd"?).
>
> - len = ch - str + 3;
> + len = ch - str + pridmax_len;
This changes the meaning of "len" to no longer be the size of the
buffer. I suppose that doesn't matter, but...
> STARTSTACKSTR(copy);
> - copy = makestrspace(len, copy);
> - memcpy(copy, str, len - 3);
> - copy[len - 3] = 'j';
> - copy[len - 2] = *ch;
> - copy[len - 1] = '\0';
> + copy = makestrspace(len + 1, copy);
> + memcpy(copy, str, len - pridmax_len);
> + memcpy(copy + len - pridmax_len, PRIdMAX, pridmax_len - 1);
> + copy[len - 1] = *ch;
> + copy[len] = '\0';
... the arithmetic is getting complicated. I think mempcpy could make
the intention clearer, like so.
char *p;
[...]
len = ch - str + strlen(PRIdMAX) + 1;
p = copy = makestrspace(len, copy);
p = mempcpy(p, str, ch - str);
p = mempcpy(p, PRIdMAX, strlen(PRIdMAX) - 1);
*p++ = *ch;
*p++ = '\0';
Like this, maybe (on top, untested)?
Signed-off-by: Jonathan Nieder <[email protected]>
---
src/bltin/printf.c | 23 ++++++++++++++++-------
1 files changed, 16 insertions(+), 7 deletions(-)
diff --git a/src/bltin/printf.c b/src/bltin/printf.c
index 4ac2ee8..0b4a4e1 100644
--- a/src/bltin/printf.c
+++ b/src/bltin/printf.c
@@ -317,16 +317,25 @@ static char *
mklong(const char *str, const char *ch)
{
char *copy;
+ char *p;
size_t len;
- size_t pridmax_len = strlen(PRIdMAX);
- len = ch - str + pridmax_len;
+ /*
+ * 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.
+ */
+
+ len = ch - str + strlen(PRIdMAX) + 1;
STARTSTACKSTR(copy);
- copy = makestrspace(len + 1, copy);
- memcpy(copy, str, len - pridmax_len);
- memcpy(copy + len - pridmax_len, PRIdMAX, pridmax_len - 1);
- copy[len - 1] = *ch;
- copy[len] = '\0';
+ p = copy = makestrspace(len, copy);
+ p = mempcpy(p, str, ch - str);
+ p = mempcpy(p, PRIdMAX, strlen(PRIdMAX) - 1);
+ *p++ = *ch;
+ *p++ = '\0';
return (copy);
}
--
1.7.5.rc2
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