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>

diff --git a/shell/ash.c b/shell/ash.c
index 6627cec9bcdcefabf2b326695a21f1c490a01ded..f4779ee2bdb5417d77a4e6e12209a7d93565572d 100644 (file)
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -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;