Allow extensions read-only access to built-in vars.

8 files changed, 202 insertions, 11 deletions

diff --git a/ChangeLog b/ChangeLog
index 2598c307..d7290276 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2012-09-14         Arnold D. Robbins     <arnold@skeeve.com>
+
+	Allow read-only access to built-in variables from extensions.
+
+	* awk.h (NO_EXT_SET): New flag.
+	* gawkapi.c (api_sym_lookup, api_sym_update_real): Set flag if off
+	limits variable instead of failing. Adjust logic.
+	(api_sym_update_scalar, api_set_array_element, api_del_array_element,
+	api_release_flattened_array): Adjust logic.
+	* gawkapi.h: Adjust documentation.
+
 2012-09-13         Arnold D. Robbins     <arnold@skeeve.com>
 
 	* configure.ac: Determination of DYNAMIC adjusted. Hopefully is
diff --git a/awk.h b/awk.h
index de425290..b0208e54 100644
--- a/awk.h
+++ b/awk.h
@@ -447,6 +447,7 @@ typedef struct exp_node {
 #		define	WSTRCUR	0x0400       /* wide str value is current */
 #		define	MPFN	0x0800       /* arbitrary-precision floating-point number */
 #		define	MPZN	0x1000       /* arbitrary-precision integer */
+#		define	NO_EXT_SET 0x2000    /* extension cannot set a value for this variable */
 
 /* type = Node_var_array */
 #		define	ARRAYMAXED	0x2000       /* array is at max size */
diff --git a/extension/ChangeLog b/extension/ChangeLog
index 1a32961a..2552a383 100644
--- a/extension/ChangeLog
+++ b/extension/ChangeLog
@@ -1,3 +1,9 @@
+2012-09-14         Arnold D. Robbins     <arnold@skeeve.com>
+
+	* testext.c (try_modify_environ): New function and test.
+	(var_test): Modified ARGC test, added additional.
+	(test_scalar_reserved): New function and test.
+
 2012-09-13         Dave Pitts            <dpitts@cozx.com>
 
 	* gawkfts.c: Add defines and ifdefs for z/OS.
diff --git a/extension/testext.c b/extension/testext.c
index bb62fa01..c11a4c85 100644
--- a/extension/testext.c
+++ b/extension/testext.c
@@ -186,6 +186,101 @@ out:
 
 /*
 BEGIN {
+	ENVIRON["testext"]++
+	try_modify_environ()
+	if ("testext" in ENVIRON)
+		print "try_del_environ() could not delete element - pass"
+	else
+		print "try_del_environ() deleted element! - fail"
+	if ("testext2" in ENVIRON)
+		print "try_del_environ() added an element - fail"
+	else
+		print "try_del_environ() could not add an element - pass"
+}
+*/
+
+static awk_value_t *
+try_modify_environ(int nargs, awk_value_t *result)
+{
+	awk_value_t value, index, newvalue;
+	awk_flat_array_t *flat_array;
+	size_t count;
+	int i;
+
+	assert(result != NULL);
+	make_number(0.0, result);
+
+	if (nargs != 0) {
+		printf("try_modify_environ: nargs not right (%d should be 0)\n", nargs);
+		goto out;
+	}
+
+	/* get ENVIRON array */
+	if (sym_lookup("ENVIRON", AWK_ARRAY, & value))
+		printf("try_modify_environ: sym_lookup of ENVIRON passed\n");
+	else {
+		printf("try_modify_environ: sym_lookup of ENVIRON failed\n");
+		goto out;
+	}
+
+	if (! get_element_count(value.array_cookie, & count)) {
+		printf("try_modify_environ: get_element_count failed\n");
+		goto out;
+	}
+
+	printf("try_modify_environ: incoming size is %lu\n", (unsigned long) count);
+
+	/* setting an array element should fail */
+	(void) make_const_string("testext2", 8, & index);
+	(void) make_const_string("a value", 7, & value);
+	if (set_array_element(value.array_cookie, & index, & newvalue)) {
+		printf("try_modify_environ: set_array_element of ENVIRON passed\n");
+	} else {
+		printf("try_modify_environ: set_array_element of ENVIRON failed\n");
+		free(index.str_value.str);
+		free(value.str_value.str);
+	}
+
+	if (! flatten_array(value.array_cookie, & flat_array)) {
+		printf("try_modify_environ: could not flatten array\n");
+		goto out;
+	}
+
+	if (flat_array->count != count) {
+		printf("try_modify_environ: flat_array->count (%lu) != count (%lu)\n",
+				(unsigned long) flat_array->count,
+				(unsigned long) count);
+		goto out;
+	}
+
+	for (i = 0; i < flat_array->count; i++) {
+		/* don't print */
+	/*
+		printf("\t%s[\"%.*s\"] = %s\n",
+			name,
+			(int) flat_array->elements[i].index.str_value.len,
+			flat_array->elements[i].index.str_value.str,
+			valrep2str(& flat_array->elements[i].value));
+	*/
+		if (strcmp("testext", flat_array->elements[i].index.str_value.str) == 0) {
+			flat_array->elements[i].flags |= AWK_ELEMENT_DELETE;
+			printf("try_modify_environ: marking element \"%s\" for deletion\n",
+				flat_array->elements[i].index.str_value.str);
+		}
+	}
+
+	if (! release_flattened_array(value.array_cookie, flat_array)) {
+		printf("try_modify_environ: could not release flattened array\n");
+		goto out;
+	}
+
+	make_number(1.0, result);
+out:
+	return result;
+}
+
+/*
+BEGIN {
 	testvar = "One Adam Twelve"
 	ret = var_test("testvar")
 	printf "var_test() returned %d, test_var = %s\n", ret, testvar
@@ -207,11 +302,18 @@ var_test(int nargs, awk_value_t *result)
 		goto out;
 	}
 
-	/* look up a reserved variable - should fail */
+	/* look up a reserved variable - should pass */
 	if (sym_lookup("ARGC", AWK_NUMBER, & value))
-		printf("var_test: sym_lookup of ARGC failed - got a value!\n");
+		printf("var_test: sym_lookup of ARGC passed - got a value!\n");
+	else
+		printf("var_test: sym_lookup of ARGC failed - did not get a value\n");
+
+	/* now try to set it - should fail */
+	value.num_value++;
+	if (sym_update("ARGC", & value))
+		printf("var_test: sym_update of ARGC passed and should not have!\n");
 	else
-		printf("var_test: sym_lookup of ARGC passed - did not get a value\n");
+		printf("var_test: sym_update of ARGC failed - correctly\n");
 
 	/* look up variable whose name is passed in, should pass */
 	if (get_argument(0, AWK_STRING, & value)) {
@@ -535,6 +637,47 @@ test_scalar(int nargs, awk_value_t *result)
 	}
 
 	if (! sym_update_scalar(the_scalar.scalar_cookie, & new_value2)) {
+		printf("test_scalar: could not update new_value2!\n");
+		goto out;
+	}
+
+	make_number(1.0, result);
+
+out:
+	return result;
+}
+
+/*
+BEGIN {
+	test_scalar_reserved()
+}
+*/
+
+/* test_scalar_reserved --- test scalar cookie on special variable */
+
+static awk_value_t *
+test_scalar_reserved(int nargs, awk_value_t *result)
+{
+	awk_value_t new_value;
+	awk_value_t the_scalar;
+
+	make_number(0.0, result);
+
+	/* look up a reserved variable - should pass */
+	if (sym_lookup("ARGC", AWK_SCALAR, & the_scalar)) {
+		printf("test_scalar_reserved: sym_lookup of ARGC passed - got a value!\n");
+	} else {
+		printf("test_scalar_reserved: sym_lookup of ARGC failed - did not get a value\n");
+		goto out;
+	}
+
+	/* updating it should fail */
+	make_number(42.0, & new_value);
+	if (! sym_update_scalar(the_scalar.scalar_cookie, & new_value)) {
+		printf("test_scalar_reserved: could not update new_value2 for ARGC - pass\n");
+	} else {
+		printf("test_scalar_reserved: was able to update new_value2 for ARGC - fail\n");
+		goto out;
 	}
 
 	make_number(1.0, result);
@@ -628,6 +771,7 @@ static void at_exit2(void *data, int exit_status)
 
 static awk_ext_func_t func_table[] = {
 	{ "dump_array_and_delete", dump_array_and_delete, 2 },
+	{ "try_modify_environ", try_modify_environ, 0 },
 	{ "var_test", var_test, 1 },
 	{ "test_errno", test_errno, 0 },
 	{ "test_array_size", test_array_size, 1 },
@@ -635,6 +779,7 @@ static awk_ext_func_t func_table[] = {
 	{ "test_array_param", test_array_param, 1 },
 	{ "print_do_lint", print_do_lint, 0 },
 	{ "test_scalar", test_scalar, 1 },
+	{ "test_scalar_reserved", test_scalar_reserved, 0 },
 };
 
 /* init_testext --- additional initialization function */
diff --git a/gawkapi.c b/gawkapi.c
index 5d372bbe..dbb8549b 100644
--- a/gawkapi.c
+++ b/gawkapi.c
@@ -489,10 +489,12 @@ api_sym_lookup(awk_ext_id_t id,
 	if (   name == NULL
 	    || *name == '\0'
 	    || result == NULL
-	    || is_off_limits_var(name)	/* most built-in vars not allowed */
 	    || (node = lookup(name)) == NULL)
 		return false;
 
+	if (is_off_limits_var(name))	/* a built-in variable */
+		node->flags |= NO_EXT_SET;
+
 	return node_to_awk_value(node, result, wanted);
 }
 
@@ -527,7 +529,6 @@ sym_update_real(awk_ext_id_t id,
 
 	if (   name == NULL
 	    || *name == '\0'
-	    || is_off_limits_var(name)	/* most built-in vars not allowed */
 	    || value == NULL)
 		return false;
 
@@ -573,6 +574,12 @@ sym_update_real(awk_ext_id_t id,
 	 * If we get here, then it exists already.  Any valid type is
 	 * OK except for AWK_ARRAY.
 	 */
+	if (   (node->flags & NO_EXT_SET) != 0
+	    || is_off_limits_var(name)) {	/* most built-in vars not allowed */
+		node->flags |= NO_EXT_SET;
+		return false;
+	}
+
 	if (    value->val_type != AWK_ARRAY
 	    && (node->type == Node_var || node->type == Node_var_new)) {
 		unref(node->var_value);
@@ -618,7 +625,8 @@ api_sym_update_scalar(awk_ext_id_t id,
 
 	if (value == NULL
 	    || node == NULL
-	    || node->type != Node_var)
+	    || node->type != Node_var
+	    || (node->flags & NO_EXT_SET) != 0)
 		return false;
 
 	/*
@@ -766,6 +774,7 @@ api_set_array_element(awk_ext_id_t id, awk_array_t a_cookie,
 	/* don't check for index len zero, null str is ok as index */
 	if (   array == NULL
 	    || array->type != Node_var_array
+	    || (array->flags & NO_EXT_SET) != 0
 	    || index == NULL
 	    || value == NULL
 	    || ! valid_subscript_type(index->val_type))
@@ -825,6 +834,7 @@ api_del_array_element(awk_ext_id_t id,
 	array = (NODE *) a_cookie;
 	if (   array == NULL
 	    || array->type != Node_var_array
+	    || (array->flags & NO_EXT_SET) != 0
 	    || index == NULL
 	    || ! valid_subscript_type(index->val_type))
 		return false;
@@ -957,7 +967,8 @@ api_release_flattened_array(awk_ext_id_t id,
 	/* free index nodes */
 	for (i = j = 0, k = 2 * array->table_size; i < k; i += 2, j++) {
 		/* Delete items flagged for delete. */
-		if ((data->elements[j].flags & AWK_ELEMENT_DELETE) != 0) {
+		if (   (data->elements[j].flags & AWK_ELEMENT_DELETE) != 0
+		    && (array->flags & NO_EXT_SET) == 0) {
 			remove_element(array, list[i]);
 		}
 		unref(list[i]);
diff --git a/gawkapi.h b/gawkapi.h
index 95effd9a..e8b7ebff 100644
--- a/gawkapi.h
+++ b/gawkapi.h
@@ -447,8 +447,8 @@ typedef struct gawk_api {
 	 * or if the wrong type was requested.
 	 * In the latter case, fills in vaule->val_type with the real type,
 	 * as described above.
-	 * Built-in variables (except PROCINFO) may not be accessed by an
-	 * extension.
+	 * Built-in variables may be accessed by an extension, but, with
+	 * the exception of PROCINFO, they may not be modified.
 	 *
 	 * 	awk_value_t val;
 	 * 	if (! api->sym_lookup(id, name, wanted, & val))
@@ -495,13 +495,15 @@ typedef struct gawk_api {
 	 * Flow is
 	 * 	sym_lookup with wanted == AWK_SCALAR
 	 * 	if returns false
-	 * 		sym_update with real initial value
+	 * 		sym_update with real initial value to install it
 	 * 		sym_lookup again with AWK_SCALAR
 	 *	else
 	 *		use the scalar cookie
 	 *
 	 * Return will be false if the new value is not one of
 	 * AWK_STRING or AWK_NUMBER.
+	 *
+	 * Here too, the built-in variables may not be updated.
 	 */
 	awk_bool_t (*api_sym_update_scalar)(awk_ext_id_t id,
 				awk_scalar_t cookie, awk_value_t *value);
@@ -522,6 +524,8 @@ typedef struct gawk_api {
 	/*
 	 * Change (or create) element in existing array with
 	 * element->index and element->value.
+	 *
+	 * ARGV and ENVIRON may not be updated.
 	 */
 	awk_bool_t (*api_set_array_element)(awk_ext_id_t id, awk_array_t a_cookie,
 					const awk_value_t *const index,
diff --git a/test/ChangeLog b/test/ChangeLog
index ff992365..4bab4796 100644
--- a/test/ChangeLog
+++ b/test/ChangeLog
@@ -1,3 +1,7 @@
+2012-09-14         Arnold D. Robbins     <arnold@skeeve.com>
+
+	* testext.ok: Updated.
+
 2012-09-11         Arnold D. Robbins     <arnold@skeeve.com>
 
 	* Makefile.am (shlib-tests): Check if DYNAMIC is enabled and
diff --git a/test/testext.ok b/test/testext.ok
index 132179c2..d291f721 100644
--- a/test/testext.ok
+++ b/test/testext.ok
@@ -10,7 +10,14 @@ dump_array_and_delete: marking element "3" for deletion
 dump_array_and_delete(pets) returned 1
 dump_array_and_delete() did remove index "3"!
 
-var_test: sym_lookup of ARGC passed - did not get a value
+try_modify_environ: sym_lookup of ENVIRON passed
+try_modify_environ: incoming size is 60
+try_modify_environ: set_array_element of ENVIRON failed
+try_modify_environ: could not flatten array
+try_del_environ() could not delete element - pass
+try_del_environ() could not add an element - pass
+var_test: sym_lookup of ARGC passed - got a value!
+var_test: sym_update of ARGC failed - correctly
 var_test: sym_update("testvar") succeeded
 var_test() returned 1, test_var = 42
 
@@ -57,6 +64,8 @@ test_scalar(over) returned 1, the_scalar is over
 test_scalar(the) returned 1, the_scalar is the
 test_scalar(lazy) returned 1, the_scalar is lazy
 test_scalar(dog) returned 1, the_scalar is dog
+test_scalar_reserved: sym_lookup of ARGC passed - got a value!
+test_scalar_reserved: could not update new_value2 for ARGC - pass
 answer_num = 42
 message_string = hello, world
 new_array["hello"] = "world"