[PATCH v2] posix: Fix some crashes in wordexp [BZ #18096]

[Julian Squires <julian@cipht.net>]

Without these fixes, the first three included tests segfault (on a
NULL dereference); the fourth aborts on an assertion, which is itself
unnecessary.

Signed-off-by: Julian Squires <julian@cipht.net>
---
v2: removed the assert under seen_hash as requested.  Thanks for the
review.

 posix/wordexp-test.c |  4 ++++
 posix/wordexp.c      | 11 ++++-------
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/posix/wordexp-test.c b/posix/wordexp-test.c
index f7a591149b..bae27d6cee 100644
--- a/posix/wordexp-test.c
+++ b/posix/wordexp-test.c
@@ -117,6 +117,8 @@ struct test_case_struct
     { 0, NULL, "$((010+0x10))", 0, 1, { "24" }, IFS },
     { 0, NULL, "$((-010+0x10))", 0, 1, { "8" }, IFS },
     { 0, NULL, "$((-0x10+010))", 0, 1, { "-8" }, IFS },
+    { 0, NULL, "$(())", 0, 1, { "0", }, IFS },
+    { 0, NULL, "$[]", 0, 1, { "0", }, IFS },
 
     /* Advanced parameter expansion */
     { 0, NULL, "${var:-bar}", 0, 1, { "bar", }, IFS },
@@ -138,6 +140,8 @@ struct test_case_struct
     { 0, "12345", "${#var}", 0, 1, { "5", }, IFS },
     { 0, NULL, "${var:-'}'}", 0, 1, { "}", }, IFS },
     { 0, NULL, "${var-}", 0, 0, { NULL }, IFS },
+    { 0, NULL, "${a?}", 0, 0, { NULL, }, IFS },
+    { 0, NULL, "${#a=}", 0, 1, { "0", }, IFS },
 
     { 0, "pizza", "${var#${var}}", 0, 0, { NULL }, IFS },
     { 0, "pepperoni", "${var%$(echo oni)}", 0, 1, { "pepper" }, IFS },
diff --git a/posix/wordexp.c b/posix/wordexp.c
index 0da98f5b08..b34c4a939b 100644
--- a/posix/wordexp.c
+++ b/posix/wordexp.c
@@ -720,7 +720,7 @@ parse_arith (char **word, size_t *word_length, size_t *max_length,
 	      ++(*offset);
 
 	      /* Go - evaluate. */
-	      if (*expr && eval_expr (expr, &numresult) != 0)
+	      if (expr && eval_expr (expr, &numresult) != 0)
 		{
 		  free (expr);
 		  return WRDE_SYNTAX;
@@ -758,7 +758,7 @@ parse_arith (char **word, size_t *word_length, size_t *max_length,
 	      long int numresult = 0;
 
 	      /* Go - evaluate. */
-	      if (*expr && eval_expr (expr, &numresult) != 0)
+	      if (expr && eval_expr (expr, &numresult) != 0)
 		{
 		  free (expr);
 		  return WRDE_SYNTAX;
@@ -1790,7 +1790,7 @@ envsubst:
 	    {
 	      const char *str = pattern;
 
-	      if (str[0] == '\0')
+	      if (!str || str[0] == '\0')
 		str = _("parameter null or not set");
 
 	      __fxprintf (NULL, "%s: %s\n", env, str);
@@ -1883,10 +1883,7 @@ envsubst:
 			_itoa_word (value ? strlen (value) : 0,
 				    &param_length[20], 10, 0));
       if (free_value)
-	{
-	  assert (value != NULL);
-	  free (value);
-	}
+	free (value);
 
       return *word ? 0 : WRDE_NOSPACE;
     }
-- 
2.39.2