hush: fix handling of '' in ${var:+ARG}

This wasn't an ash bug in dollar_altvalue9, it was hush bug (and bash!)

function                                             old     new   delta
expand_one_var                                      2236    2254     +18
expand_vars_to_list                                 1097    1103      +6
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 24/0)               Total: 24 bytes

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

1 files changed, 9 insertions, 3 deletions

diff --git a/shell/hush.c b/shell/hush.c
index fc77b89fc..559595d2e 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -475,7 +475,6 @@
 #endif
 
 #define SPECIAL_VAR_SYMBOL_STR "\3"
-#define SPECIAL_VAR_SYMBOL_CHR '\3'
 #define SPECIAL_VAR_SYMBOL       3
 /* The "variable" with name "\1" emits string "\3". Testcase: "echo ^C" */
 #define SPECIAL_VAR_QUOTED_SVS   1
@@ -5950,6 +5949,8 @@ static int encode_then_append_var_plusminus(o_string *output, int n,
                                                 break;
                                         o_addqchr(&dest, ch);
                                 }
+                                o_addchr(&dest, SPECIAL_VAR_SYMBOL);
+                                o_addchr(&dest, SPECIAL_VAR_SYMBOL);
                                 continue;
                         }
                 }
@@ -5959,6 +5960,10 @@ static int encode_then_append_var_plusminus(o_string *output, int n,
                 }
                 if (ch == '"') {
                         dest.o_expflags ^= EXP_FLAG_ESC_GLOB_CHARS;
+                        if (dest.o_expflags) {
+                                o_addchr(&dest, SPECIAL_VAR_SYMBOL);
+                                o_addchr(&dest, SPECIAL_VAR_SYMBOL);
+                        }
                         continue;
                 }
                 if (ch == '\\') {
@@ -6565,7 +6570,7 @@ static NOINLINE int expand_vars_to_list(o_string *output, int n, char *arg)
                 case SPECIAL_VAR_QUOTED_SVS:
                         /* <SPECIAL_VAR_SYMBOL><SPECIAL_VAR_QUOTED_SVS><SPECIAL_VAR_SYMBOL> */
                         /* "^C variable", represents literal ^C char (possible in scripts) */
-                        o_addchr(output, SPECIAL_VAR_SYMBOL_CHR);
+                        o_addchr(output, SPECIAL_VAR_SYMBOL);
                         arg++;
                         break;
 #if ENABLE_HUSH_TICK
@@ -6627,7 +6632,8 @@ static NOINLINE int expand_vars_to_list(o_string *output, int n, char *arg)
                 o_addstr(output, arg);
                 debug_print_list("expand_vars_to_list[b]", output, n);
         } else if (output->length == o_get_last_ptr(output, n) /* expansion is empty */
-         && !(cant_be_null & 0x80) /* and all vars were not quoted. */
+         && !(cant_be_null & 0x80)   /* and all vars were not quoted */
+         && !output->has_quoted_part
         ) {
                 n--;
                 /* allow to reuse list[n] later without re-growth */