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ash: use alloca to get rid of setjmp 

Now that the only thing protected by setjmp/longjmp is the saved string,
we can allocate it on the stack to get rid of the jump.

Based on commit bd35d8e from git://git.kernel.org/pub/scm/utils/dash/dash.git
by Herbert Xu.

function                                             old     new   delta
readtoken1                                          3182    3116     -66
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-66)             Total: -66 bytes

Signed-off-by: Ron Yorston <rmy@frippery.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Ron Yorston 2015-07-01 16:46:18 +01:00 committed by Denys Vlasenko
parent f54a487bb4
commit 072fc60f29
1 changed files with 2 additions and 34 deletions
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36
shell/ash.c
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@ -11132,19 +11132,6 @@ readtoken1(int c, int syntax, char *eofmark, int striptabs)
IF_ASH_BASH_COMPAT(smallint bash_dollar_squote = 0;)
#if __GNUC__
/* Avoid longjmp clobbering */
(void) &out;
(void) &quotef;
(void) &dblquote;
(void) &varnest;
(void) &arinest;
(void) &parenlevel;
(void) &dqvarnest;
(void) &oldstyle;
(void) &prevsyntax;
(void) &syntax;
#endif
startlinno = g_parsefile->linno;
bqlist = NULL;
quotef = 0;
@ -11609,30 +11596,16 @@ parsesub: {
parsebackq: {
struct nodelist **nlpp;
union node *n;
char *volatile str;
struct jmploc jmploc;
struct jmploc *volatile savehandler;
char *str;
size_t savelen;
smallint saveprompt = 0;
#ifdef __GNUC__
(void) &saveprompt;
#endif
if (setjmp(jmploc.loc)) {
free(str);
exception_handler = savehandler;
longjmp(exception_handler->loc, 1);
}
INT_OFF;
str = NULL;
savelen = out - (char *)stackblock();
if (savelen > 0) {
str = ckmalloc(savelen);
str = alloca(savelen);
memcpy(str, stackblock(), savelen);
}
savehandler = exception_handler;
exception_handler = &jmploc;
INT_ON;
if (oldstyle) {
/* We must read until the closing backquote, giving special
* treatment to some slashes, and then push the string and
@ -11731,12 +11704,7 @@ parsebackq: {
if (str) {
memcpy(out, str, savelen);
STADJUST(savelen, out);
INT_OFF;
free(str);
str = NULL;
INT_ON;
}
exception_handler = savehandler;
USTPUTC(CTLBACKQ, out);
if (oldstyle)
goto parsebackq_oldreturn;