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lib/vsprintf.c: reduce stack use in number() 

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>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rasmus Villemoes 2015-04-15 16:17:05 -07:00 committed by Linus Torvalds
parent 51be17dfff
commit e26c12c777
1 changed files with 1 additions and 6 deletions
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7
lib/vsprintf.c
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@ -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..." */ /* we are called with base 8, 10 or 16, only, thus don't need "G..." */
static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */ static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
char tmp[66]; char tmp[3 * sizeof(num)];
char sign; char sign;
char locase; char locase;
int need_pfx = ((spec.flags & SPECIAL) && spec.base != 10); 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; i = 0;
if (num < spec.base) if (num < spec.base)
tmp[i++] = digits[num] | locase; 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 */ else if (spec.base != 10) { /* 8 or 16 */
int mask = spec.base - 1; int mask = spec.base - 1;
int shift = 3; int shift = 3;