hush: bit better comments in redirect code. No logic changes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 38 insertions, 11 deletions

diff --git a/shell/hush.c b/shell/hush.c
index b41d9d04b..9b45b312f 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -6099,10 +6099,12 @@ static int setup_redirects(struct command *prog, int squirrel[])
 
         for (redir = prog->redirects; redir; redir = redir->next) {
                 if (redir->rd_type == REDIRECT_HEREDOC2) {
-                        /* rd_fd<<HERE case */
-                        if (squirrel && redir->rd_fd < 3
+                        /* "rd_fd<<HERE" case */
+                        if (redir->rd_fd <= 2
+                         && squirrel
                          && squirrel[redir->rd_fd] < 0
                         ) {
+                                /* Save old fds 0..2 if redirect uses them */
                                 squirrel[redir->rd_fd] = dup(redir->rd_fd);
                         }
                         /* for REDIRECT_HEREDOC2, rd_filename holds _contents_
@@ -6114,7 +6116,7 @@ static int setup_redirects(struct command *prog, int squirrel[])
                 }
 
                 if (redir->rd_dup == REDIRFD_TO_FILE) {
-                        /* rd_fd<*>file case (<*> is <,>,>>,<>) */
+                        /* "rd_fd<*>file" case (<*> is <,>,>>,<>) */
                         char *p;
                         if (redir->rd_filename == NULL) {
                                 /* Something went wrong in the parse.
@@ -6127,20 +6129,33 @@ static int setup_redirects(struct command *prog, int squirrel[])
                         openfd = open_or_warn(p, mode);
                         free(p);
                         if (openfd < 0) {
-                        /* this could get lost if stderr has been redirected, but
-                         * bash and ash both lose it as well (though zsh doesn't!) */
-//what the above comment tries to say?
+                                /* Error message from open_or_warn can be lost
+                                 * if stderr has been redirected, but bash
+                                 * and ash both lose it as well
+                                 * (though zsh doesn't!)
+                                 */
                                 return 1;
                         }
                 } else {
-                        /* rd_fd<*>rd_dup or rd_fd<*>- cases */
+                        /* "rd_fd<*>rd_dup" or "rd_fd<*>-" cases */
                         openfd = redir->rd_dup;
                 }
 
                 if (openfd != redir->rd_fd) {
-                        if (squirrel && redir->rd_fd < 3
+                        if (redir->rd_fd <= 2
+                         && squirrel
                          && squirrel[redir->rd_fd] < 0
                         ) {
+                                /* Save old fds 0..2 if redirect uses them */
+//FIXME: script fd's also need this! "sh SCRIPT" and SCRIPT has "echo FOO 3>&-":
+// open("SCRIPT", O_RDONLY)          = 3
+// fcntl(3, F_SETFD, FD_CLOEXEC)     = 0
+// read(3, "echo FOO 3>&-\n....", 4096) = N
+// close(3)                          = 0
+// write(1, "FOO\n", 4)              = 4
+// ...
+// read(3, 0x205f8e0, 4096)          = -1 EBADF <== BUG
+//
                                 squirrel[redir->rd_fd] = dup(redir->rd_fd);
                         }
                         if (openfd == REDIRFD_CLOSE) {
@@ -6159,7 +6174,7 @@ static int setup_redirects(struct command *prog, int squirrel[])
 static void restore_redirects(int squirrel[])
 {
         int i, fd;
-        for (i = 0; i < 3; i++) {
+        for (i = 0; i <= 2; i++) {
                 fd = squirrel[i];
                 if (fd != -1) {
                         /* We simply die on error */
@@ -7144,6 +7159,7 @@ static NOINLINE int run_pipe(struct pipe *pi)
                                 if (x->b_function == builtin_exec && argv_expanded[1] == NULL) {
                                         debug_printf("exec with redirects only\n");
                                         rcode = setup_redirects(command, NULL);
+                                        /* rcode=1 can be if redir file can't be opened */
                                         goto clean_up_and_ret1;
                                 }
                         }
@@ -7270,9 +7286,20 @@ static NOINLINE int run_pipe(struct pipe *pi)
                         if (pipefds.rd > 1)
                                 close(pipefds.rd);
                         /* Like bash, explicit redirects override pipes,
-                         * and the pipe fd is available for dup'ing. */
-                        if (setup_redirects(command, NULL))
+                         * and the pipe fd (fd#1) is available for dup'ing:
+                         * "cmd1 2>&1 | cmd2": fd#1 is duped to fd#2, thus stderr
+                         * of cmd1 goes into pipe.
+                         */
+                        if (setup_redirects(command, NULL)) {
+                                /* Happens when redir file can't be opened:
+                                 * $ hush -c 'echo FOO >&2 | echo BAR 3>/qwe/rty; echo BAZ'
+                                 * FOO
+                                 * hush: can't open '/qwe/rty': No such file or directory
+                                 * BAZ
+                                 * (echo BAR is not executed, it hits _exit(1) below)
+                                 */
                                 _exit(1);
+                        }
 
                         /* Stores to nommu_save list of env vars putenv'ed
                          * (NOMMU, on MMU we don't need that) */