sh: Expand here documents in the current process.

Expand here documents at the same point other redirections are expanded but
use a non-fork subshell environment (like simple command substitutions) for
compatibility. Substitition errors result in an empty here document like
before.

As a result, a fork is avoided for short (<4K) expanded here documents.

Unexpanded here documents (with quoted end marker after <<) are not affected
by this change. They already only forked when >4K.

Side effects:
* Order of expansion is slightly different.
* Slow expansions are not executed in parallel with the redirected command.
* A non-fork subshell environment is subtly different from a forked process.
This commit is contained in:
Jilles Tjoelker 2013-02-03 15:54:57 +00:00
parent de17cbcc7e
commit 4dc6bdd3e7
5 changed files with 48 additions and 24 deletions

@ -92,6 +92,7 @@ static void evalfor(union node *, int);
static union node *evalcase(union node *);
static void evalsubshell(union node *, int);
static void evalredir(union node *, int);
static void exphere(union node *, struct arglist *);
static void expredir(union node *);
static void evalpipe(union node *);
static int is_valid_fast_cmdsubst(union node *n);
@ -488,6 +489,37 @@ evalredir(union node *n, int flags)
}
static void
exphere(union node *redir, struct arglist *fn)
{
struct jmploc jmploc;
struct jmploc *savehandler;
struct localvar *savelocalvars;
int need_longjmp = 0;
redir->nhere.expdoc = nullstr;
savelocalvars = localvars;
localvars = NULL;
forcelocal++;
savehandler = handler;
if (setjmp(jmploc.loc))
need_longjmp = exception != EXERROR && exception != EXEXEC;
else {
handler = &jmploc;
expandarg(redir->nhere.doc, fn, 0);
redir->nhere.expdoc = fn->list->text;
INTOFF;
}
handler = savehandler;
forcelocal--;
poplocalvars();
localvars = savelocalvars;
if (need_longjmp)
longjmp(handler->loc, 1);
INTON;
}
/*
* Compute the names of the files in a redirection list.
*/
@ -516,6 +548,9 @@ expredir(union node *n)
fixredir(redir, fn.list->text, 1);
}
break;
case NXHERE:
exphere(redir, &fn);
break;
}
}
}

@ -127,19 +127,6 @@ collate_range_cmp(wchar_t c1, wchar_t c2)
return (wcscoll(s1, s2));
}
/*
* Expand shell variables and backquotes inside a here document.
* union node *arg the document
* int fd; where to write the expanded version
*/
void
expandhere(union node *arg, int fd)
{
expandarg(arg, (struct arglist *)NULL, 0);
xwrite(fd, stackblock(), expdest - stackblock());
}
static char *
stputs_quotes(const char *data, const char *syntax, char *p)
{

@ -57,7 +57,6 @@ struct arglist {
union node;
void expandhere(union node *, int);
void expandarg(union node *, struct arglist *, int);
void expari(int);
void rmescapes(char *);

@ -138,6 +138,7 @@ NXHERE nhere # fd<<!
next nodeptr # next redirection in list
fd int # file descriptor being redirected
doc nodeptr # input to command (NARG node)
expdoc temp char *expdoc # actual document (for NXHERE)
NNOT nnot # ! command (actually pipeline)
type int

@ -251,18 +251,23 @@ movefd:
static int
openhere(union node *redir)
{
char *p;
int pip[2];
int len = 0;
if (pipe(pip) < 0)
error("Pipe call failed: %s", strerror(errno));
if (redir->type == NHERE) {
len = strlen(redir->nhere.doc->narg.text);
if (len <= PIPESIZE) {
xwrite(pip[1], redir->nhere.doc->narg.text, len);
goto out;
}
if (redir->type == NXHERE)
p = redir->nhere.expdoc;
else
p = redir->nhere.doc->narg.text;
len = strlen(p);
if (len <= PIPESIZE) {
xwrite(pip[1], p, len);
goto out;
}
if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
close(pip[0]);
signal(SIGINT, SIG_IGN);
@ -270,10 +275,7 @@ openhere(union node *redir)
signal(SIGHUP, SIG_IGN);
signal(SIGTSTP, SIG_IGN);
signal(SIGPIPE, SIG_DFL);
if (redir->type == NHERE)
xwrite(pip[1], redir->nhere.doc->narg.text, len);
else
expandhere(redir->nhere.doc, pip[1]);
xwrite(pip[1], p, len);
_exit(0);
}
out: