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EXPERIMENTAL optimisation for “sh -c 'foo'” to equal “sh -c 'exit foo'” iff

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several conditions are met as outlined below; for more background, refer to
http://www.FreeBSD.org/cgi/query-pr.cgi?pr=113860

We don’t yet optimise 「% sh -c '{ echo a; sleep 10;}&'; sleep 1; ps T」 so
the FreeBSD® sh approach cannot work for us, but scanning the “sh -c” argu‐
ment for disallowed characters and, if not, setting a flag that enables the
shell to exec the tree when parsed as TCOM *and not c_trap()* was possible.

Disallowed characters are currently C_QUOTE except space, that is:
Tab Newline " # $ & ' ( ) * ; < = > ? [ \ ] ` |

This should catch all cases of magic, variables, subshells, pipelines, etc.
This commit is contained in:
tg 2012-10-21 21:26:41 +00:00
parent 1f43cc907d
commit bebb2d2254
3 changed files with 38 additions and 6 deletions
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11
exec.c
View File

@ -23,7 +23,7 @@
#include "sh.h"
__RCSID("$MirOS: src/bin/mksh/exec.c,v 1.101 2012/10/03 17:24:18 tg Exp $");
__RCSID("$MirOS: src/bin/mksh/exec.c,v 1.102 2012/10/21 21:26:39 tg Exp $");
#ifndef MKSH_DEFAULT_EXECSHELL
#define MKSH_DEFAULT_EXECSHELL "/bin/sh"
@ -604,11 +604,20 @@ comexec(struct op *t, struct tbl * volatile tp, const char **ap,
else
/* go on, use the builtin */
break;
#endif
#ifndef MKSH_SMALL
} else if (tp->val.f == c_trap) {
t->u.evalflags &= ~DOTCOMEXEC;
break;
#endif
} else
break;
tp = findcom(ap[0], fcflags & (FC_BI|FC_FUNC));
}
#ifndef MKSH_SMALL
if (t->u.evalflags & DOTCOMEXEC)
flags |= XEXEC;
#endif
l_expand = e->loc;
if (keepasn_ok && (!ap[0] || (tp && (tp->flag & KEEPASN))))
type_flags = 0;

25
main.c
View File

@ -34,7 +34,7 @@
#include <locale.h>
#endif
__RCSID("$MirOS: src/bin/mksh/main.c,v 1.229 2012/10/21 17:16:45 tg Exp $");
__RCSID("$MirOS: src/bin/mksh/main.c,v 1.230 2012/10/21 21:26:40 tg Exp $");
extern char **environ;
@ -464,6 +464,16 @@ main_init(int argc, const char *argv[], Source **sp, struct block **lp)
s = pushs(SSTRINGCMDLINE, ATEMP);
if (!(s->start = s->str = argv[argi++]))
errorf("%s %s", "-c", "requires an argument");
#ifndef MKSH_SMALL
while (*s->str) {
if (*s->str != ' ' && ctype(*s->str, C_QUOTE))
break;
s->str++;
}
if (!*s->str)
s->flags |= SF_MAYEXEC;
s->str = s->start;
#endif
#ifdef MKSH_MIDNIGHTBSD01ASH_COMPAT
/* compatibility to MidnightBSD 0.1 /bin/sh (kludge) */
if (Flag(FSH) && argv[argi] && !strcmp(argv[argi], "--"))
@ -818,7 +828,9 @@ shell(Source * volatile s, volatile bool toplevel)
}
t = compile(s, sfirst);
sfirst = false;
if (t != NULL && t->type == TEOF) {
if (!t)
goto source_no_tree;
if (t->type == TEOF) {
if (wastty && Flag(FIGNOREEOF) && --attempts > 0) {
shellf("Use 'exit' to leave mksh\n");
s->type = SSTDIN;
@ -838,12 +850,17 @@ shell(Source * volatile s, volatile bool toplevel)
break;
}
}
if (t && (!Flag(FNOEXEC) || (s->flags & SF_TTY)))
#ifndef MKSH_SMALL
else if ((s->flags & SF_MAYEXEC) && t->type == TCOM)
t->u.evalflags |= DOTCOMEXEC;
#endif
if (!Flag(FNOEXEC) || (s->flags & SF_TTY))
exstat = execute(t, 0, NULL);
if (t != NULL && t->type != TEOF && interactive && really_exit)
if (t->type != TEOF && interactive && really_exit)
really_exit = false;
source_no_tree:
reclaim();
}
quitenv(NULL);

8
sh.h
View File

@ -157,7 +157,7 @@
#endif
#ifdef EXTERN
__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.592 2012/10/03 17:24:23 tg Exp $");
__RCSID("$MirOS: src/bin/mksh/sh.h,v 1.593 2012/10/21 21:26:41 tg Exp $");
#endif
#define MKSH_VERSION "R40 2012/10/03"
@ -1343,6 +1343,9 @@ struct ioword {
#define DOTEMP BIT(8) /* dito: in word part of ${..[%#=?]..} */
#define DOVACHECK BIT(9) /* var assign check (for typeset, set, etc) */
#define DOMARKDIRS BIT(10) /* force markdirs behaviour */
#ifndef MKSH_SMALL
#define DOTCOMEXEC BIT(11) /* not an eval flag, used by sh -c hack */
#endif
/*
* The arguments of [[ .. ]] expressions are kept in t->args[] and flags
@ -1486,6 +1489,9 @@ struct source {
#define SF_ALIASEND BIT(2) /* faking space at end of alias */
#define SF_TTY BIT(3) /* type == SSTDIN & it is a tty */
#define SF_HASALIAS BIT(4) /* u.tblp valid (SALIAS, SEOF) */
#ifndef MKSH_SMALL
#define SF_MAYEXEC BIT(5) /* special sh -c optimisation hack */
#endif
typedef union {
int i;