hush: do not drop backslash from eval 'echo ok\'

newer bash does not drop it, most other shells too

function                                             old     new   delta
unbackslash                                           39      57     +18
parse_stream                                        2753    2751      -2
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/1 up/down: 18/-2)              Total: 16 bytes

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

6 files changed, 22 insertions, 8 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 713219b6e..6f8bc9042 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -203,7 +203,7 @@
  * TODO:
  * singleword+noglob expansion:
  *   v='a b'; [[ $v = 'a b' ]]; echo 0:$?
- *   [[ /bin/* ]]; echo 0:$?
+ *   [[ /bin/n* ]]; echo 0:$?
  * -a/-o are not AND/OR ops! (they are just strings)
  * quoting needs to be considered (-f is an operator, "-f" and ""-f are not; etc)
  * = is glob match operator, not equality operator: STR = GLOB
diff --git a/shell/ash_test/ash-parsing/bkslash_eof1.right b/shell/ash_test/ash-parsing/bkslash_eof1.right
new file mode 100644
index 000000000..6c6df0b0c
--- /dev/null
+++ b/shell/ash_test/ash-parsing/bkslash_eof1.right
@@ -0,0 +1 @@
+ok\
diff --git a/shell/ash_test/ash-parsing/bkslash_eof1.tests b/shell/ash_test/ash-parsing/bkslash_eof1.tests
new file mode 100755
index 000000000..97629cb13
--- /dev/null
+++ b/shell/ash_test/ash-parsing/bkslash_eof1.tests
@@ -0,0 +1 @@
+eval 'echo ok\'
diff --git a/shell/ash_test/ash-redir/redir_exec1.right b/shell/ash_test/ash-redir/redir_exec1.right
index d4393d10c..c98455bf5 100644
--- a/shell/ash_test/ash-redir/redir_exec1.right
+++ b/shell/ash_test/ash-redir/redir_exec1.right
@@ -1,2 +1,2 @@
-redir_exec1.tests: line 1: can't create /cant/be/created: nonexistent directory
+./redir_exec1.tests: line 1: can't create /cant/be/created: nonexistent directory
 First
diff --git a/shell/hush.c b/shell/hush.c
index 3afb70cb0..523fc1a31 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -83,7 +83,7 @@
  * Status of [[ support:
  * [[ args ]] are CMD_SINGLEWORD_NOGLOB:
  *   v='a b'; [[ $v = 'a b' ]]; echo 0:$?
- *   [[ /bin/* ]]; echo 0:$?
+ *   [[ /bin/n* ]]; echo 0:$?
  * TODO:
  * &&/|| are AND/OR ops, -a/-o are not
  * quoting needs to be considered (-f is an operator, "-f" and ""-f are not; etc)
@@ -1426,8 +1426,19 @@ static char *unbackslash(char *src)
 {
         char *dst = src = strchrnul(src, '\\');
         while (1) {
-                if (*src == '\\')
+                if (*src == '\\') {
                         src++;
+                        if (*src != '\0') {
+                                /* \x -> x */
+                                *dst++ = *src++;
+                                continue;
+                        }
+                        /* else: "\<nul>". Do not delete this backslash.
+                         * Testcase: eval 'echo ok\'
+                         */
+                        *dst++ = '\\';
+                        /* fallthrough */
+                }
                 if ((*dst++ = *src++) == '\0')
                         break;
         }
@@ -5392,16 +5403,17 @@ static struct pipe *parse_stream(char **pstring,
                         continue; /* get next char */
                 case '\\':
                         /*nommu_addchr(&ctx.as_string, '\\'); - already done */
+                        o_addchr(&ctx.word, '\\');
                         ch = i_getch(input);
                         if (ch == EOF) {
-                                /* Ignore this '\'. Testcase: eval 'echo Ok\' */
-#if !BB_MMU
+                                /* Testcase: eval 'echo Ok\' */
+
+#if 0 /* bash-4.3.43 was removing backslash, but 4.4.19 retains it, most other shells too */
                                 /* Remove trailing '\' from ctx.as_string */
                                 ctx.as_string.data[--ctx.as_string.length] = '\0';
 #endif
                                 continue; /* get next char */
                         }
-                        o_addchr(&ctx.word, '\\');
                         /* Example: echo Hello \2>file
                          * we need to know that word 2 is quoted
                          */
diff --git a/shell/hush_test/hush-parsing/bkslash_eof1.right b/shell/hush_test/hush-parsing/bkslash_eof1.right
index 9766475a4..6c6df0b0c 100644
--- a/shell/hush_test/hush-parsing/bkslash_eof1.right
+++ b/shell/hush_test/hush-parsing/bkslash_eof1.right
@@ -1 +1 @@
-ok
+ok\