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Subject[PATCH 2/4] lib/vsprintf.c: Reduce stack use in number()
Date
At least since the initial git commit, when base was passed as a
separate parameter, number() has only been called with bases 8, 10 and
16. I'm guessing that 66 was to accommodate 64 0/1, a sign and a '\0',
but the buffer is only used for the actual digits. Octal digits carry
3 bits of information, so 24 is enough. Spell that 3*sizeof(num) so
one less place needs to be changed should long long ever be 128
bits. Also remove the commented-out code that would handle an
arbitrary base.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---
lib/vsprintf.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 318d583fe862..98f1ce907d3d 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -386,7 +386,7 @@ char *number(char *buf, char *end, unsigned long long num,
/* we are called with base 8, 10 or 16, only, thus don't need "G..." */
static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */

- char tmp[66];
+ char tmp[3 * sizeof(num)];
char sign;
char locase;
int need_pfx = ((spec.flags & SPECIAL) && spec.base != 10);
@@ -423,11 +423,6 @@ char *number(char *buf, char *end, unsigned long long num,
i = 0;
if (num < spec.base)
tmp[i++] = digits[num] | locase;
- /* Generic code, for any base:
- else do {
- tmp[i++] = (digits[do_div(num,base)] | locase);
- } while (num != 0);
- */
else if (spec.base != 10) { /* 8 or 16 */
int mask = spec.base - 1;
int shift = 3;
--
2.1.3


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