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.

1 files changed, 0 insertions, 13 deletions

diff --git a/bin/sh/expand.c b/bin/sh/expand.c
index d43cc35..107f798 100644
--- a/bin/sh/expand.c
+++ b/bin/sh/expand.c
@@ -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)
 {