Allow creation of constants from extensions.

11 files changed, 194 insertions, 10 deletions

diff --git a/ChangeLog b/ChangeLog
index 04bd15d1..bd444d2b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2012-07-12         Arnold D. Robbins     <arnold@skeeve.com>
+
+	Allow creation of constants. Thanks to John Haque for the
+	implementation concept.
+
+	* gawk_api.h (api_sym_constant): Create a constant.
+	* gawk_api.h (api_sym_update_real): Renamed from api_sym_update.
+	Add is_const paramater and do the right thing if true.
+	(api_sym_update, api_sym_constant): Call api_sym_update_real
+	in the correct way.
+	(set_constant): New function.
+
 2012-07-11         Andrew J. Schorr     <aschorr@telemetry-investments.com>
 
 	* gawkapi.h: Fix typo in comment.
diff --git a/extension/ChangeLog b/extension/ChangeLog
index 4eab7d7a..ce8d6b78 100644
--- a/extension/ChangeLog
+++ b/extension/ChangeLog
@@ -4,6 +4,9 @@
 	* Makefile.am: Build fnmatch extension.
 	* configure.ac: Look for fnmatch.h and fnmatch function.
 
+	* fnmatch.c (init_fnmatch): Use sym_constant for FNM_NOMATCH.
+	* testext.c (dl_load): Use sym_constant for answer_num.
+
 2012-07-11         Arnold D. Robbins     <arnold@skeeve.com>
 
 	* filefuncs.c (array_set, do_stat): Use make_const_string.
diff --git a/extension/fnmatch.c b/extension/fnmatch.c
index 7f050dcd..aa8a7307 100644
--- a/extension/fnmatch.c
+++ b/extension/fnmatch.c
@@ -137,7 +137,7 @@ init_fnmatch(void)
 	awk_array_t new_array;
 	int i;
 
-	if (! sym_update("FNM_NOMATCH", make_number(FNM_NOMATCH, & value))) {
+	if (! sym_constant("FNM_NOMATCH", make_number(FNM_NOMATCH, & value))) {
 		warning(ext_id, "fnmatch init: could not add FNM_NOMATCH variable");
 		errors++;
 	}
diff --git a/extension/testext.c b/extension/testext.c
index d446fb8e..dc3002a9 100644
--- a/extension/testext.c
+++ b/extension/testext.c
@@ -623,8 +623,8 @@ BEGIN {
 */
 
 	/* install some variables */
-	if (! sym_update("answer_num", make_number(42, & value)))
-		printf("testext: sym_update(\"answer_num\") failed!\n");
+	if (! sym_constant("answer_num", make_number(42, & value)))
+		printf("testext: sym_constant(\"answer_num\") failed!\n");
 
 	if (! sym_update("message_string",
 			make_const_string(message, strlen(message), & value)))
diff --git a/gawkapi.c b/gawkapi.c
index b6d83acb..e8d50e8c 100644
--- a/gawkapi.c
+++ b/gawkapi.c
@@ -26,6 +26,7 @@
 #include "awk.h"
 
 static awk_bool_t node_to_awk_value(NODE *node, awk_value_t *result, awk_valtype_t wanted);
+static void set_constant();
 
 /*
  * Get the count'th paramater, zero-based.
@@ -460,10 +461,13 @@ api_sym_lookup_scalar(awk_ext_id_t id,
 	return node_to_awk_value(node, result, wanted);
 }
 
-/* api_sym_update --- update a symbol's value, see gawkapi.h for semantics */
+/* api_sym_update_real --- update a symbol's value, see gawkapi.h for semantics */
 
 static awk_bool_t
-api_sym_update(awk_ext_id_t id, const char *name, awk_value_t *value)
+sym_update_real(awk_ext_id_t id,
+		const char *name,
+		awk_value_t *value,
+		bool is_const)
 {
 	NODE *node;
 	NODE *array_node;
@@ -503,6 +507,8 @@ api_sym_update(awk_ext_id_t id, const char *name, awk_value_t *value)
 					Node_var);
 			unref(node->var_value);
 			node->var_value = awk_value_to_node(value);
+			if (is_const)
+				node->var_assign = set_constant;
 		}
 		return true;
 	}
@@ -518,6 +524,9 @@ api_sym_update(awk_ext_id_t id, const char *name, awk_value_t *value)
 		if (node->type == Node_var || node->type == Node_var_new) {
 			unref(node->var_value);
 			node->var_value = awk_value_to_node(value);
+			/* let the extension change its own variable */
+			if (is_const)
+				node->var_assign = set_constant;
 		} else {
 			return false;
 		}
@@ -530,6 +539,26 @@ api_sym_update(awk_ext_id_t id, const char *name, awk_value_t *value)
 	return true;
 }
 
+/* api_sym_update --- update a symbol, non-constant */
+
+static awk_bool_t
+api_sym_update(awk_ext_id_t id,
+		const char *name,
+		awk_value_t *value)
+{
+	return sym_update_real(id, name, value, false);
+}
+
+/* api_sym_update --- update a symbol, constant */
+
+static awk_bool_t
+api_sym_constant(awk_ext_id_t id,
+		const char *name,
+		awk_value_t *value)
+{
+	return sym_update_real(id, name, value, true);
+}
+
 /* api_sym_update_scalar --- update a scalar cookie */
 
 static awk_bool_t
@@ -864,6 +893,7 @@ gawk_api_t api_impl = {
 	api_sym_lookup,
 	api_sym_lookup_scalar,
 	api_sym_update,
+	api_sym_constant,
 	api_sym_update_scalar,
 
 	api_get_array_element,
@@ -897,3 +927,11 @@ update_ext_api()
 {
 	api_impl.do_flags[0] = (do_lint ? 1 : 0);
 }
+
+/* set_constant --- prevent awk code from changing a constant */
+
+static void
+set_constant()
+{
+	fatal(_("cannot assign to defined constant"));
+}
diff --git a/gawkapi.h b/gawkapi.h
index 50ca327a..a84fbf52 100644
--- a/gawkapi.h
+++ b/gawkapi.h
@@ -334,7 +334,15 @@ typedef struct gawk_api {
 	 * In fact, using this to update an array is not allowed, either.
 	 * Such an attempt returns false.
 	 */
-	awk_bool_t (*api_sym_update)(awk_ext_id_t id, const char *name, awk_value_t *value);
+	awk_bool_t (*api_sym_update)(awk_ext_id_t id,
+				const char *name,
+				awk_value_t *value);
+	/*
+	 * Install a constant value.
+	 */
+	awk_bool_t (*api_sym_constant)(awk_ext_id_t id,
+				const char *name,
+				awk_value_t *value);
 
 	/*
 	 * Work with a scalar cookie.
@@ -445,6 +453,8 @@ typedef struct gawk_api {
 	(api->api_sym_lookup_scalar(ext_id, scalar_cookie, wanted, result))
 #define sym_update(name, value) \
 	(api->api_sym_update(ext_id, name, value))
+#define sym_constant(name, value) \
+	(api->api_sym_constant(ext_id, name, value))
 #define sym_update_scalar(scalar_cookie, value) \
 	(api->api_sym_update_scalar)(ext_id, scalar_cookie, value)
 
diff --git a/test/ChangeLog b/test/ChangeLog
index 019d2f34..50dcd27c 100644
--- a/test/ChangeLog
+++ b/test/ChangeLog
@@ -3,6 +3,9 @@
 	* Makefile.am (fnmatch): New test.
 	* fnmatch.awk, fnmatch.ok: New files.
 
+	* Makefile.am (assignconst): New test.
+	* assignconst.awk, assignconst.ok: New files.
+
 2012-06-28         Andrew J. Schorr     <aschorr@telemetry-investments.com>
 
 	* time.awk: Avoid possibly throwing a spurious error by protecting
diff --git a/test/Makefile.am b/test/Makefile.am
index a244c6a0..78fd3117 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -102,6 +102,8 @@ EXTRA_DIST = \
 	asort.ok \
 	asorti.awk \
 	asorti.ok \
+	assignconst.awk \
+	assignconst.ok \
 	awkpath.ok \
 	back89.awk \
 	back89.in \
@@ -891,8 +893,8 @@ LOCALE_CHARSET_TESTS = \
 	mbprintf1 mbprintf2 mbprintf3 rebt8b2 rtlenmb sort1 sprintfc
 
 SHLIB_TESTS = \
-	fnmatch filefuncs fork fork2 ordchr ordchr2 readfile rwarray \
-	testext time
+	assignconst fnmatch filefuncs fork fork2 ordchr ordchr2 \
+	readfile rwarray testext time
 
 # List of the tests which should be run with --lint option:
 NEED_LINT = \
@@ -1594,6 +1596,13 @@ testext::
 	@$(AWK) -f testext.awk >_$@ 2>&1 || echo EXIT CODE: $$? >>_$@
 	@-$(CMP) $(srcdir)/$@.ok _$@ && rm -f _$@ testext.awk
 
+assignconst:
+	@echo $@
+	@for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14; \
+	do $(AWK) -f $(srcdir)/$@.awk $$i ; \
+	done 2>&1 | grep -v at_exit > _$@
+	@-$(CMP) $(srcdir)/$@.ok _$@ && rm -f _$@
+
 # Targets generated for other tests:
 include Maketests
 
diff --git a/test/Makefile.in b/test/Makefile.in
index 61e32b1b..d12139cf 100644
--- a/test/Makefile.in
+++ b/test/Makefile.in
@@ -314,6 +314,8 @@ EXTRA_DIST = \
 	asort.ok \
 	asorti.awk \
 	asorti.ok \
+	assignconst.awk \
+	assignconst.ok \
 	awkpath.ok \
 	back89.awk \
 	back89.in \
@@ -1099,8 +1101,8 @@ LOCALE_CHARSET_TESTS = \
 	mbprintf1 mbprintf2 mbprintf3 rebt8b2 rtlenmb sort1 sprintfc
 
 SHLIB_TESTS = \
-	fnmatch filefuncs fork fork2 ordchr ordchr2 readfile rwarray \
-	testext time
+	assignconst fnmatch filefuncs fork fork2 ordchr ordchr2 \
+	readfile rwarray testext time
 
 
 # List of the tests which should be run with --lint option:
@@ -1975,6 +1977,13 @@ testext::
 	@$(AWK) '/^(@load|BEGIN)/,/^}/' $(top_srcdir)/extension/testext.c > testext.awk
 	@$(AWK) -f testext.awk >_$@ 2>&1 || echo EXIT CODE: $$? >>_$@
 	@-$(CMP) $(srcdir)/$@.ok _$@ && rm -f _$@ testext.awk
+
+assignconst:
+	@echo $@
+	@for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14; \
+	do $(AWK) -f $(srcdir)/$@.awk $$i ; \
+	done 2>&1 | grep -v at_exit > _$@
+	@-$(CMP) $(srcdir)/$@.ok _$@ && rm -f _$@
 Gt-dummy:
 # file Maketests, generated from Makefile.am by the Gentests program
 addcomma:
diff --git a/test/assignconst.awk b/test/assignconst.awk
new file mode 100644
index 00000000..907987c7
--- /dev/null
+++ b/test/assignconst.awk
@@ -0,0 +1,58 @@
+@load "testext"
+
+BEGIN {
+	print ""
+	print "test:", ARGV[1]
+	switch (ARGV[1] + 0) {
+	case 1:
+		answer_num = 43
+		break
+	case 2:
+		++answer_num
+		break
+	case 3:
+		--answer_num
+		break
+	case 4:
+		answer_num++
+		break
+	case 5:
+		answer_num--
+		break
+	case 6:
+		answer_num += 1
+		break
+	case 7:
+		answer_num -= 1
+		break
+	case 8:
+		answer_num *= 1
+		break
+	case 9:
+		answer_num /= 1
+		break
+	case 10:
+		answer_num ^= 1
+		break
+	case 11:
+		answer_num = answer_num "foo"
+		break
+	case 12:
+		sub(/2/, "3", answer_num)
+		break
+	case 13:
+		a[1] = 1
+		for (answer_num in a)
+			print answer_num, a[answer_num]
+		break
+	case 14:
+		test_func(answer_num)
+		break
+	}
+}
+
+function test_func(val)
+{
+	val++
+	print "in test_func, val now =", val
+}
diff --git a/test/assignconst.ok b/test/assignconst.ok
new file mode 100644
index 00000000..e2bc7494
--- /dev/null
+++ b/test/assignconst.ok
@@ -0,0 +1,42 @@
+
+test: 1
+gawk: ./assignconst.awk:8: fatal: cannot assign to defined constant
+
+test: 2
+gawk: ./assignconst.awk:11: fatal: cannot assign to defined constant
+
+test: 3
+gawk: ./assignconst.awk:14: fatal: cannot assign to defined constant
+
+test: 4
+gawk: ./assignconst.awk:17: fatal: cannot assign to defined constant
+
+test: 5
+gawk: ./assignconst.awk:20: fatal: cannot assign to defined constant
+
+test: 6
+gawk: ./assignconst.awk:23: fatal: cannot assign to defined constant
+
+test: 7
+gawk: ./assignconst.awk:26: fatal: cannot assign to defined constant
+
+test: 8
+gawk: ./assignconst.awk:29: fatal: cannot assign to defined constant
+
+test: 9
+gawk: ./assignconst.awk:32: fatal: cannot assign to defined constant
+
+test: 10
+gawk: ./assignconst.awk:35: fatal: cannot assign to defined constant
+
+test: 11
+gawk: ./assignconst.awk:38: fatal: cannot assign to defined constant
+
+test: 12
+gawk: ./assignconst.awk:41: fatal: cannot assign to defined constant
+
+test: 13
+gawk: ./assignconst.awk:45: fatal: cannot assign to defined constant
+
+test: 14
+in test_func, val now = 43