Improved __future__ parser; still more to do

Makefile.pre.in: add target future.o

Include/compile.h: define PyFutureFeaters and PyNode_Future()
                   add c_future slot to struct compiling

Include/symtable.h: add st_future slot to struct symtable

Python/future.c: implementation of PyNode_Future()

Python/compile.c: use PyNode_Future() for nested_scopes support

Python/symtable.c: include compile.h to pick up PyFutureFeatures decl

1 files changed, 146 insertions, 0 deletions

diff --git a/Python/future.c b/Python/future.c
new file mode 100644
index 0000000..f67abc9
--- /dev/null
+++ b/Python/future.c
@@ -0,0 +1,146 @@
+#include "Python.h"
+#include "node.h"
+#include "token.h"
+#include "graminit.h"
+#include "compile.h"
+#include "symtable.h"
+
+#define UNDEFINED_FUTURE_FEATURE "future feature %.100s is not defined"
+
+static int
+future_check_features(PyFutureFeatures *ff, node *n)
+{
+	int i;
+	char *feature;
+
+	REQ(n, import_stmt); /* must by from __future__ import ... */
+
+	for (i = 3; i < NCH(n); ++i) {
+		feature = STR(CHILD(CHILD(n, i), 0));
+		if (strcmp(feature, FUTURE_NESTED_SCOPES) == 0) {
+			ff->ff_nested_scopes = 1;
+		} else {
+			PyErr_Format(PyExc_SyntaxError,
+				     UNDEFINED_FUTURE_FEATURE, feature);
+			return -1;
+		}
+	}
+	return 0;
+}
+
+/* Relevant portions of the grammar:
+
+single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
+file_input: (NEWLINE | stmt)* ENDMARKER
+stmt: simple_stmt | compound_stmt
+simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE
+small_stmt: expr_stmt | print_stmt  | del_stmt | pass_stmt | flow_stmt | import_stmt | global_stmt | exec_stmt | assert_stmt
+import_stmt: 'import' dotted_as_name (',' dotted_as_name)* | 'from' dotted_name 'import' ('*' | import_as_name (',' import_as_name)*)
+import_as_name: NAME [NAME NAME]
+dotted_as_name: dotted_name [NAME NAME]
+dotted_name: NAME ('.' NAME)*
+*/
+
+/* future_parse() return values:
+   -1 indicates an error occurred, e.g. unknown feature name
+   0 indicates no feature was found
+   1 indicates a feature was found
+*/
+
+static int
+future_parse(PyFutureFeatures *ff, node *n)
+{
+	int i, r, found;
+ loop:
+
+/*	fprintf(stderr, "future_parse(%d, %d, %s)\n",
+		TYPE(n), NCH(n), (n == NULL) ? "NULL" : STR(n));
+*/
+	switch (TYPE(n)) {
+
+	case file_input:
+		for (i = 0; i < NCH(n); i++) {
+			node *ch = CHILD(n, i);
+			if (TYPE(ch) == stmt) {
+				n = ch;
+				goto loop;
+			}
+		}
+		return 0;
+
+	case simple_stmt:
+		if (NCH(n) == 1) {
+			REQ(CHILD(n, 0), small_stmt);
+			n = CHILD(n, 0);
+			goto loop;
+		}
+		found = 0;
+		for (i = 0; i < NCH(n); ++i)
+			if (TYPE(CHILD(n, i)) == small_stmt) {
+				r = future_parse(ff, CHILD(n, i));
+				if (r < 1) {
+					ff->ff_last_lineno = n->n_lineno;
+					ff->ff_n_simple_stmt = i;
+					return r;
+				} else
+					found++;
+			}
+		if (found)
+			return 1;
+		else
+			return 0;
+	
+	case stmt:
+		if (TYPE(CHILD(n, 0)) == simple_stmt) {
+			n = CHILD(n, 0);
+			goto loop;
+		} else {
+			REQ(CHILD(n, 0), compound_stmt);
+			ff->ff_last_lineno = n->n_lineno;
+			return 0;
+		}
+
+	case small_stmt:
+		n = CHILD(n, 0);
+		goto loop;
+
+	case import_stmt: {
+		node *name;
+
+		if (STR(CHILD(n, 0))[0] != 'f') { /* from */
+			ff->ff_last_lineno = n->n_lineno;
+			return 0;
+		}
+		name = CHILD(n, 1);
+		if (strcmp(STR(CHILD(name, 0)), "__future__") != 0)
+			return 0;
+		if (future_check_features(ff, n) < 0)
+			return -1;
+		return 1;
+	}
+
+	default:
+		ff->ff_last_lineno = n->n_lineno;
+		return 0;
+	}
+}
+
+PyFutureFeatures *
+PyNode_Future(node *n, char *filename)
+{
+	PyFutureFeatures *ff;
+
+	ff = (PyFutureFeatures *)PyMem_Malloc(sizeof(PyFutureFeatures));
+	if (ff == NULL)
+		return NULL;
+	ff->ff_last_lineno = 0;
+	ff->ff_n_simple_stmt = -1;
+	ff->ff_nested_scopes = 0;
+
+	if (future_parse(ff, n) < 0) {
+		PyMem_Free((void *)ff);
+		return NULL;
+	}
+	return ff;
+}
+