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ash: Expand here-documents in the current shell environment

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Upstream commit:

    Date: Sun, 11 Nov 2007 15:27:00 +0800
    Expand here-documents in the current shell environment

    Previously we always expanded here-documents in a subshell.  This is
    contrary to the POSIX specification and how other shells behave.  What's
    more this slows down many expansions due to the extra fork (however, it
    must be said that it is possible for it speed up certain expansions by
    running it simultaneously with the command on two CPUs).

    This patch move the expansion into the current shell environment.

    Test case:

            unset a
            cat <<- EOF > /dev/null
                    ${a=NOT}
            EOF
            echo ${a}BAD

    Old result:

            BAD

    New result:

            NOTBAD

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2020-02-22 20:25:03 +01:00
parent c08993f40c
commit c2058ec98c
3 changed files with 22 additions and 13 deletions
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29
shell/ash.c
View File

@ -5444,22 +5444,29 @@ stoppedjobs(void)
* the pipe without forking.
*/
/* openhere needs this forward reference */
static void expandhere(union node *arg, int fd);
static void expandhere(union node *arg);
static int
openhere(union node *redir)
{
char *p;
int pip[2];
size_t len = 0;
if (pipe(pip) < 0)
ash_msg_and_raise_perror("can't create pipe");
if (redir->type == NHERE) {
len = strlen(redir->nhere.doc->narg.text);
if (len <= PIPE_BUF) {
full_write(pip[1], redir->nhere.doc->narg.text, len);
goto out;
}
p = redir->nhere.doc->narg.text;
if (redir->type == NXHERE) {
expandhere(redir->nhere.doc);
p = stackblock();
}
len = strlen(p);
if (len <= PIPE_BUF) {
xwrite(pip[1], p, len);
goto out;
}
if (forkshell((struct job *)NULL, (union node *)NULL, FORK_NOJOB) == 0) {
/* child */
close(pip[0]);
@ -5468,10 +5475,7 @@ openhere(union node *redir)
ignoresig(SIGHUP); //signal(SIGHUP, SIG_IGN);
ignoresig(SIGTSTP); //signal(SIGTSTP, SIG_IGN);
signal(SIGPIPE, SIG_DFL);
if (redir->type == NHERE)
full_write(pip[1], redir->nhere.doc->narg.text, len);
else /* NXHERE */
expandhere(redir->nhere.doc, pip[1]);
xwrite(pip[1], p, len);
_exit(EXIT_SUCCESS);
}
out:
@ -8016,10 +8020,9 @@ expandarg(union node *arg, struct arglist *arglist, int flag)
* Expand shell variables and backquotes inside a here document.
*/
static void
expandhere(union node *arg, int fd)
expandhere(union node *arg)
{
expandarg(arg, (struct arglist *)NULL, EXP_QUOTED);
full_write(fd, stackblock(), expdest - (char *)stackblock());
}
/*

1
shell/ash_test/ash-heredoc/heredoc_side_effects.right Normal file
View File

@ -0,0 +1 @@
NO BUG

5
shell/ash_test/ash-heredoc/heredoc_side_effects.tests Executable file
View File

@ -0,0 +1,5 @@
unset a
cat <<EOF >/dev/null
${a=NO}
EOF
echo $a BUG