emo/busybox
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

awk: use static tmpvars instead of nvalloc(1)ed ones

Browse Source 
ptest() was using this idea already.

As far as I can see, this is safe. Ttestsuite passes.

One downside is that a temporary from e.g. printf invocation
won't be freed until the next printf call.

function                                             old     new   delta
awk_printf                                           481     468     -13
as_regex                                             137     111     -26
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-39)             Total: -39 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2021-07-01 17:50:26 +02:00
parent 1573487e21
commit 8b4c429025
1 changed files with 33 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
editors/awk.c
View File

@ -559,7 +559,9 @@ struct globals2 {
unsigned evaluate__seed;
regex_t evaluate__sreg;
var ptest__v;
var ptest__tmpvar;
var awk_printf__tmpvar;
var as_regex__tmpvar;
tsplitter exec_builtin__tspl;
@ -1775,14 +1777,19 @@ static node *mk_splitter(const char *s, tsplitter *spl)
static regex_t *as_regex(node *op, regex_t *preg)
{
int cflags;
var *tmpvar;
const char *s;
if ((op->info & OPCLSMASK) == OC_REGEXP) {
return icase ? op->r.ire : op->l.re;
}
tmpvar = nvalloc(1);
s = getvar_s(evaluate(op, tmpvar));
#define TMPVAR (&G.as_regex__tmpvar)
//tmpvar = nvalloc(1);
// We use a single "static" tmpvar (instead of on-stack or malloced one)
// to decrease memory consumption in deeply-recursive awk programs.
// The rule to work safely is to never call evaluate() while our static
// TMPVAR's value is still needed.
s = getvar_s(evaluate(op, TMPVAR));
cflags = icase ? REG_EXTENDED | REG_ICASE : REG_EXTENDED;
/* Testcase where REG_EXTENDED fails (unpaired '{'):
@ -1794,7 +1801,8 @@ static regex_t *as_regex(node *op, regex_t *preg)
cflags &= ~REG_EXTENDED;
xregcomp(preg, s, cflags);
}
nvfree(tmpvar, 1);
//nvfree(tmpvar, 1);
#undef TMPVAR
return preg;
}
@ -2105,8 +2113,11 @@ static int hashwalk_next(var *v)
/* evaluate node, return 1 when result is true, 0 otherwise */
static int ptest(node *pattern)
{
/* ptest__v is "static": to save stack space? */
return istrue(evaluate(pattern, &G.ptest__v));
// We use a single "static" tmpvar (instead of on-stack or malloced one)
// to decrease memory consumption in deeply-recursive awk programs.
// The rule to work safely is to never call evaluate() while our static
// TMPVAR's value is still needed.
return istrue(evaluate(pattern, &G.ptest__tmpvar));
}
/* read next record from stream rsm into a variable v */
@ -2243,12 +2254,18 @@ static char *awk_printf(node *n, int *len)
const char *s1;
int i, j, incr, bsize;
char c, c1;
var *tmpvar, *arg;
var *arg;
tmpvar = nvalloc(1);
//TODO: above, to avoid allocating a single temporary var, take a pointer
//to a temporary that our caller (evaluate()) already has?
fmt = f = xstrdup(getvar_s(evaluate(nextarg(&n), tmpvar)));
//tmpvar = nvalloc(1);
#define TMPVAR (&G.awk_printf__tmpvar)
// We use a single "static" tmpvar (instead of on-stack or malloced one)
// to decrease memory consumption in deeply-recursive awk programs.
// The rule to work safely is to never call evaluate() while our static
// TMPVAR's value is still needed.
fmt = f = xstrdup(getvar_s(evaluate(nextarg(&n), TMPVAR)));
// ^^^^^^^^^ here we immediately strdup() the value, so the later call
// to evaluate() potentially recursing into another awk_printf() can't
// mangle the value.
i = 0;
while (*f) {
@ -2268,7 +2285,7 @@ static char *awk_printf(node *n, int *len)
f++;
c1 = *f;
*f = '\0';
arg = evaluate(nextarg(&n), tmpvar);
arg = evaluate(nextarg(&n), TMPVAR);
j = i;
if (c == 'c' || !c) {
@ -2289,7 +2306,9 @@ static char *awk_printf(node *n, int *len)
}
free(fmt);
nvfree(tmpvar, 1);
// nvfree(tmpvar, 1);
#undef TMPVAR
b = xrealloc(b, i + 1);
b[i] = '\0';
#if ENABLE_FEATURE_AWK_GNU_EXTENSIONS