Merge ast-branch to head

This change implements a new bytecode compiler, based on a
transformation of the parse tree to an abstract syntax defined in
Parser/Python.asdl.

The compiler implementation is not complete, but it is in stable
enough shape to run the entire test suite excepting two disabled
tests.

1 files changed, 1178 insertions, 63 deletions

diff --git a/Python/symtable.c b/Python/symtable.c
index 5ca2041..bd41202 100644
--- a/Python/symtable.c
+++ b/Python/symtable.c
@@ -1,48 +1,35 @@
 #include "Python.h"
+#include "Python-ast.h"
+#include "code.h"
 #include "compile.h"
 #include "symtable.h"
-#include "graminit.h"
 #include "structmember.h"
 
-/* The compiler uses this function to load a PySymtableEntry object
-   for a code block.  Each block is loaded twice, once during the
-   symbol table pass and once during the code gen pass.  Entries
-   created during the first pass are cached for the second pass, using
-   the st_symbols dictionary.  
-
-   The cache is keyed by st_nscopes.  Each code block node in a
-   module's parse tree can be assigned a unique id based on the order
-   in which the nodes are visited by the compiler.  This strategy
-   works so long as the symbol table and codegen passes visit the same
-   nodes in the same order.
-*/
+/* two error strings used for warnings */
+#define GLOBAL_AFTER_ASSIGN \
+"name '%.400s' is assigned to before global declaration"
 
+#define GLOBAL_AFTER_USE \
+"name '%.400s' is used prior to global declaration"
 
-PyObject *
-PySymtableEntry_New(struct symtable *st, char *name, int type, int lineno)
+PySTEntryObject *
+PySTEntry_New(struct symtable *st, identifier name, block_ty block,
+	      void *key, int lineno)
 {
-	PySymtableEntryObject *ste = NULL;
+	PySTEntryObject *ste = NULL;
 	PyObject *k, *v;
 
-	k = PyInt_FromLong(st->st_nscopes++);
+	k = PyLong_FromVoidPtr(key);
 	if (k == NULL)
 		goto fail;
-	v = PyDict_GetItem(st->st_symbols, k);
-	if (v) {
-		Py_DECREF(k);
-		Py_INCREF(v);
-		return v;
-	}
-	
-	ste = (PySymtableEntryObject *)PyObject_New(PySymtableEntryObject,
-						    &PySymtableEntry_Type);
+	ste = (PySTEntryObject *)PyObject_New(PySTEntryObject,
+					      &PySTEntry_Type);
 	ste->ste_table = st;
 	ste->ste_id = k;
+	ste->ste_tmpname = 0;
 
-	v = PyString_FromString(name);
-	if (v == NULL)
-		goto fail;
-	ste->ste_name = v;
+	ste->ste_name = name;
+	Py_INCREF(name);
 	
 	v = PyDict_New();
 	if (v == NULL)
@@ -59,61 +46,46 @@ PySymtableEntry_New(struct symtable *st, char *name, int type, int lineno)
 	    goto fail;
 	ste->ste_children = v;
 
-	ste->ste_optimized = 0;
+	ste->ste_type = block;
+	ste->ste_unoptimized = 0;
+	ste->ste_nested = 0;
+	ste->ste_free = 0;
+	ste->ste_varargs = 0;
+	ste->ste_varkeywords = 0;
 	ste->ste_opt_lineno = 0;
 	ste->ste_tmpname = 0;
 	ste->ste_lineno = lineno;
-	switch (type) {
-	case funcdef:
-	case lambdef:
-	case testlist_gexp: /* generator expression */
-	case argument:      /* generator expression */
-		ste->ste_type = TYPE_FUNCTION;
-		break;
-	case classdef:
-		ste->ste_type = TYPE_CLASS;
-		break;
-	case single_input:
-	case eval_input:
-	case file_input:
-		ste->ste_type = TYPE_MODULE;
-		break;
-	}
 
-	if (st->st_cur == NULL)
-		ste->ste_nested = 0;
-	else if (st->st_cur->ste_nested 
-		 || st->st_cur->ste_type == TYPE_FUNCTION)
+	if (st->st_cur != NULL &&
+	    (st->st_cur->ste_nested ||
+	     st->st_cur->ste_type == FunctionBlock))
 		ste->ste_nested = 1;
-	else
-		ste->ste_nested = 0;
 	ste->ste_child_free = 0;
 	ste->ste_generator = 0;
 
 	if (PyDict_SetItem(st->st_symbols, ste->ste_id, (PyObject *)ste) < 0)
 	    goto fail;
 	
-	return (PyObject *)ste;
+	return ste;
  fail:
 	Py_XDECREF(ste);
 	return NULL;
 }
 
 static PyObject *
-ste_repr(PySymtableEntryObject *ste)
+ste_repr(PySTEntryObject *ste)
 {
 	char buf[256];
 
 	PyOS_snprintf(buf, sizeof(buf),
 		      "<symtable entry %.100s(%ld), line %d>",
 		      PyString_AS_STRING(ste->ste_name),
-		      PyInt_AS_LONG(ste->ste_id),
-		      ste->ste_lineno);
+		      PyInt_AS_LONG(ste->ste_id), ste->ste_lineno);
 	return PyString_FromString(buf);
 }
 
 static void
-ste_dealloc(PySymtableEntryObject *ste)
+ste_dealloc(PySTEntryObject *ste)
 {
 	ste->ste_table = NULL;
 	Py_XDECREF(ste->ste_id);
@@ -124,7 +96,7 @@ ste_dealloc(PySymtableEntryObject *ste)
 	PyObject_Del(ste);
 }
 
-#define OFF(x) offsetof(PySymtableEntryObject, x)
+#define OFF(x) offsetof(PySTEntryObject, x)
 
 static PyMemberDef ste_memberlist[] = {
 	{"id",       T_OBJECT, OFF(ste_id), READONLY},
@@ -134,16 +106,14 @@ static PyMemberDef ste_memberlist[] = {
 	{"children", T_OBJECT, OFF(ste_children), READONLY},
 	{"type",     T_INT,    OFF(ste_type), READONLY},
 	{"lineno",   T_INT,    OFF(ste_lineno), READONLY},
-	{"optimized",T_INT,    OFF(ste_optimized), READONLY},
-	{"nested",   T_INT,    OFF(ste_nested), READONLY},
 	{NULL}
 };
 
-PyTypeObject PySymtableEntry_Type = {
+PyTypeObject PySTEntry_Type = {
 	PyObject_HEAD_INIT(&PyType_Type)
 	0,
 	"symtable entry",
-	sizeof(PySymtableEntryObject),
+	sizeof(PySTEntryObject),
 	0,
 	(destructor)ste_dealloc,                /* tp_dealloc */
 	0,                                      /* tp_print */
@@ -180,3 +150,1148 @@ PyTypeObject PySymtableEntry_Type = {
 	0,					/* tp_alloc */
 	0,					/* tp_new */
 };
+
+static int symtable_analyze(struct symtable *st);
+static int symtable_warn(struct symtable *st, char *msg);
+static int symtable_enter_block(struct symtable *st, identifier name, 
+				block_ty block, void *ast, int lineno);
+static int symtable_exit_block(struct symtable *st, void *ast);
+static int symtable_visit_stmt(struct symtable *st, stmt_ty s);
+static int symtable_visit_expr(struct symtable *st, expr_ty s);
+static int symtable_visit_genexp(struct symtable *st, expr_ty s);
+static int symtable_visit_arguments(struct symtable *st, arguments_ty);
+static int symtable_visit_excepthandler(struct symtable *st, excepthandler_ty);
+static int symtable_visit_alias(struct symtable *st, alias_ty);
+static int symtable_visit_comprehension(struct symtable *st, comprehension_ty);
+static int symtable_visit_keyword(struct symtable *st, keyword_ty);
+static int symtable_visit_slice(struct symtable *st, slice_ty);
+static int symtable_visit_params(struct symtable *st, asdl_seq *args, int top);
+static int symtable_visit_params_nested(struct symtable *st, asdl_seq *args);
+static int symtable_implicit_arg(struct symtable *st, int pos);
+
+
+static identifier top = NULL, lambda = NULL;
+
+#define GET_IDENTIFIER(VAR) \
+	((VAR) ? (VAR) : ((VAR) = PyString_InternFromString(# VAR)))
+
+#define DUPLICATE_ARGUMENT \
+"duplicate argument '%s' in function definition"
+
+static struct symtable *
+symtable_new(void)
+{
+	struct symtable *st;
+
+	st = (struct symtable *)PyMem_Malloc(sizeof(struct symtable));
+	if (st == NULL)
+		return NULL;
+
+	st->st_filename = NULL;
+	if ((st->st_stack = PyList_New(0)) == NULL)
+		goto fail;
+	if ((st->st_symbols = PyDict_New()) == NULL)
+		goto fail; 
+	st->st_cur = NULL;
+	st->st_tmpname = 0;
+	st->st_private = NULL;
+	return st;
+ fail:
+	PySymtable_Free(st);
+	return NULL;
+}
+
+struct symtable *
+PySymtable_Build(mod_ty mod, const char *filename, PyFutureFeatures *future)
+{
+	struct symtable *st = symtable_new();
+	asdl_seq *seq;
+	int i;
+
+	if (st == NULL)
+		return st;
+	st->st_filename = filename;
+	st->st_future = future;
+	symtable_enter_block(st, GET_IDENTIFIER(top), ModuleBlock, 
+			     (void *)mod, 0);
+	st->st_top = st->st_cur;
+	st->st_cur->ste_unoptimized = OPT_TOPLEVEL;
+	/* Any other top-level initialization? */
+	switch (mod->kind) {
+	case Module_kind:
+		seq = mod->v.Module.body;
+		for (i = 0; i < asdl_seq_LEN(seq); i++)
+			if (!symtable_visit_stmt(st, asdl_seq_GET(seq, i)))
+				goto error;
+		break;
+	case Expression_kind:
+		if (!symtable_visit_expr(st, mod->v.Expression.body))
+			goto error;
+		break;
+	case Interactive_kind:
+		seq = mod->v.Interactive.body;
+		for (i = 0; i < asdl_seq_LEN(seq); i++)
+			if (!symtable_visit_stmt(st, asdl_seq_GET(seq, i)))
+				goto error;
+		break;
+	case Suite_kind:
+		PyErr_SetString(PyExc_RuntimeError,
+				"this compiler does not handle Suites");
+		return NULL;
+	}
+	if (!symtable_exit_block(st, (void *)mod))
+		return NULL;
+	if (symtable_analyze(st))
+		return st;
+ error:
+	PySymtable_Free(st);
+	return NULL;
+}
+
+void
+PySymtable_Free(struct symtable *st)
+{
+	Py_XDECREF(st->st_symbols);
+	Py_XDECREF(st->st_stack);
+	PyMem_Free((void *)st);
+}
+
+PySTEntryObject *
+PySymtable_Lookup(struct symtable *st, void *key)
+{
+	PyObject *k, *v;
+
+	k = PyLong_FromVoidPtr(key);
+	if (k == NULL)
+		return NULL;
+	v = PyDict_GetItem(st->st_symbols, k);
+	if (v) {
+		assert(PySTEntry_Check(v));
+		Py_DECREF(k);
+		Py_INCREF(v);
+		return (PySTEntryObject *)v;
+	}
+	else {
+		PyErr_SetString(PyExc_KeyError,
+				"unknown symbol table entry");
+		return NULL;
+	}
+}
+
+int 
+PyST_GetScope(PySTEntryObject *ste, PyObject *name)
+{
+	PyObject *v = PyDict_GetItem(ste->ste_symbols, name);
+	if (!v)
+		return 0;
+	assert(PyInt_Check(v));
+	return (PyInt_AS_LONG(v) >> SCOPE_OFF) & SCOPE_MASK;
+}
+
+
+/* Analyze raw symbol information to determine scope of each name.
+
+   The next several functions are helpers for PySymtable_Analyze(),
+   which determines whether a name is local, global, or free.  In addition, 
+   it determines which local variables are cell variables; they provide
+   bindings that are used for free variables in enclosed blocks.  
+
+   There are also two kinds of free variables, implicit and explicit.  An 
+   explicit global is declared with the global statement.  An implicit
+   global is a free variable for which the compiler has found no binding
+   in an enclosing function scope.  The implicit global is either a global
+   or a builtin.  Python's module and class blocks use the xxx_NAME opcodes
+   to handle these names to implement slightly odd semantics.  In such a
+   block, the name is treated as global until it is assigned to; then it
+   is treated as a local.
+
+   The symbol table requires two passes to determine the scope of each name.
+   The first pass collects raw facts from the AST: the name is a parameter 
+   here, the name is used by not defined here, etc.  The second pass analyzes
+   these facts during a pass over the PySTEntryObjects created during pass 1.
+
+   When a function is entered during the second pass, the parent passes
+   the set of all name bindings visible to its children.  These bindings 
+   are used to determine if the variable is free or an implicit global.
+   After doing the local analysis, it analyzes each of its child blocks
+   using an updated set of name bindings.  
+
+   The children update the free variable set.  If a local variable is free 
+   in a child, the variable is marked as a cell.  The current function must 
+   provide runtime storage for the variable that may outlive the function's 
+   frame.  Cell variables are removed from the free set before the analyze
+   function returns to its parent.
+   
+   The sets of bound and free variables are implemented as dictionaries
+   mapping strings to None.
+*/
+
+#define SET_SCOPE(DICT, NAME, I) { \
+	PyObject *o = PyInt_FromLong(I); \
+	if (!o) \
+		return 0; \
+	if (PyDict_SetItem((DICT), (NAME), o) < 0) \
+		return 0; \
+}
+
+/* Decide on scope of name, given flags.
+
+   The dicts passed in as arguments are modified as necessary.
+   ste is passed so that flags can be updated.
+*/
+
+static int 
+analyze_name(PySTEntryObject *ste, PyObject *dict, PyObject *name, int flags,
+	     PyObject *bound, PyObject *local, PyObject *free, 
+	     PyObject *global)
+{
+	if (flags & DEF_GLOBAL) {
+		if (flags & DEF_PARAM) {
+			PyErr_Format(PyExc_SyntaxError,
+				     "name '%s' is local and global",
+				     PyString_AS_STRING(name));
+			return 0;
+		}
+		SET_SCOPE(dict, name, GLOBAL_EXPLICIT);
+		if (PyDict_SetItem(global, name, Py_None) < 0)
+			return 0;
+		if (bound && PyDict_GetItem(bound, name)) {
+			if (PyDict_DelItem(bound, name) < 0)
+				return 0;
+		}
+		return 1;
+	}
+	if (flags & DEF_BOUND) {
+		SET_SCOPE(dict, name, LOCAL);
+		if (PyDict_SetItem(local, name, Py_None) < 0)
+			return 0;
+		if (PyDict_GetItem(global, name)) {
+			if (PyDict_DelItem(global, name) < 0)
+				return 0;
+		}
+		return 1;
+	}
+	/* If an enclosing block has a binding for this name, it
+	   is a free variable rather than a global variable.
+	   Note that having a non-NULL bound implies that the block
+	   is nested.
+	*/
+	if (bound && PyDict_GetItem(bound, name)) {
+		SET_SCOPE(dict, name, FREE);
+		ste->ste_free = 1;
+		if (PyDict_SetItem(free, name, Py_None) < 0)
+			return 0;
+		return 1;
+	}
+	/* If a parent has a global statement, then call it global
+	   explicit?  It could also be global implicit.
+	 */
+	else if (global && PyDict_GetItem(global, name)) {
+		SET_SCOPE(dict, name, GLOBAL_EXPLICIT);
+		return 1;
+	}
+	else {
+		if (ste->ste_nested)
+			ste->ste_free = 1;
+		SET_SCOPE(dict, name, GLOBAL_IMPLICIT);
+		return 1;
+	}
+	return 0; /* Can't get here */
+}
+
+#undef SET_SCOPE
+
+/* If a name is defined in free and also in locals, then this block
+   provides the binding for the free variable.  The name should be
+   marked CELL in this block and removed from the free list.
+
+   Note that the current block's free variables are included in free.
+   That's safe because no name can be free and local in the same scope.
+*/
+
+static int
+analyze_cells(PyObject *scope, PyObject *free)
+{
+        PyObject *name, *v, *w;
+	int flags, pos = 0, success = 0;
+
+	w = PyInt_FromLong(CELL);
+	if (!w)
+		return 0;
+	while (PyDict_Next(scope, &pos, &name, &v)) {
+		assert(PyInt_Check(v));
+		flags = PyInt_AS_LONG(v);
+		if (flags != LOCAL)
+			continue;
+		if (!PyDict_GetItem(free, name))
+			continue;
+		/* Replace LOCAL with CELL for this name, and remove
+		   from free. It is safe to replace the value of name 
+		   in the dict, because it will not cause a resize.
+		 */
+		if (PyDict_SetItem(scope, name, w) < 0)
+			goto error;
+		if (!PyDict_DelItem(free, name) < 0)
+			goto error;
+	}
+	success = 1;
+ error:
+	Py_DECREF(w);
+	return success;
+}
+
+/* Check for illegal statements in unoptimized namespaces */
+static int
+check_unoptimized(const PySTEntryObject* ste) {
+	char buf[300];
+
+	if (ste->ste_type == ModuleBlock || !ste->ste_unoptimized
+	    || !(ste->ste_free || ste->ste_child_free))
+		return 1;
+
+	const char* trailer = (ste->ste_child_free ? 
+		       "contains a nested function with free variables" :
+			       "is a nested function");
+
+	switch (ste->ste_unoptimized) {
+	case OPT_TOPLEVEL: /* exec / import * at top-level is fine */
+	case OPT_EXEC: /* qualified exec is fine */
+		return 1;
+	case OPT_IMPORT_STAR:
+		PyOS_snprintf(buf, sizeof(buf), 
+			      "import * is not allowed in function '%.100s' "
+			      "because it is %s",
+			      PyString_AS_STRING(ste->ste_name), trailer);
+		break;
+	case OPT_BARE_EXEC:
+		PyOS_snprintf(buf, sizeof(buf),
+			      "unqualified exec is not allowed in function "
+			      "'%.100s' it %s",
+			      PyString_AS_STRING(ste->ste_name), trailer);
+		break;
+	default:
+		PyOS_snprintf(buf, sizeof(buf), 
+			      "function '%.100s' uses import * and bare exec, "
+			      "which are illegal because it %s",
+			      PyString_AS_STRING(ste->ste_name), trailer);
+		break;
+	}
+
+	PyErr_SetString(PyExc_SyntaxError, buf);
+	PyErr_SyntaxLocation(ste->ste_table->st_filename, 
+			     ste->ste_opt_lineno);
+	return 0;
+}
+
+/* Enter the final scope information into the st_symbols dict. 
+ * 
+ * All arguments are dicts.  Modifies symbols, others are read-only.
+*/
+static int
+update_symbols(PyObject *symbols, PyObject *scope, 
+               PyObject *bound, PyObject *free, int class)
+{
+	PyObject *name, *v, *u, *w, *free_value = NULL;
+	int i, flags, pos = 0;
+
+	while (PyDict_Next(symbols, &pos, &name, &v)) {
+		assert(PyInt_Check(v));
+		flags = PyInt_AS_LONG(v);
+		w = PyDict_GetItem(scope, name);
+		assert(w && PyInt_Check(w));
+		i = PyInt_AS_LONG(w);
+		flags |= (i << SCOPE_OFF);
+		u = PyInt_FromLong(flags);
+		if (PyDict_SetItem(symbols, name, u) < 0) {
+			Py_DECREF(u);
+			return 0;
+		}
+		Py_DECREF(u);
+	}
+
+        free_value = PyInt_FromLong(FREE << SCOPE_OFF);
+        if (!free_value)
+		return 0;
+
+        /* add a free variable when it's only use is for creating a closure */
+        pos = 0;
+	while (PyDict_Next(free, &pos, &name, &v)) {
+		PyObject *o = PyDict_GetItem(symbols, name);
+
+		if (o) {
+			/* It could be a free variable in a method of
+			   the class that has the same name as a local
+			   or global in the class scope.
+			*/
+			if  (class && 
+			     PyInt_AS_LONG(o) & (DEF_BOUND | DEF_GLOBAL)) {
+				int i = PyInt_AS_LONG(o) | DEF_FREE_CLASS;
+				o = PyInt_FromLong(i);
+				if (!o) {
+					Py_DECREF(free_value);
+					return 0;
+				}
+				if (PyDict_SetItem(symbols, name, o) < 0) {
+					Py_DECREF(o);
+					Py_DECREF(free_value);
+					return 0;
+				}
+			}
+			/* else it's not free, probably a cell */
+			continue;
+		}
+		if (!PyDict_GetItem(bound, name))
+			continue;       /* it's a global */
+
+		if (PyDict_SetItem(symbols, name, free_value) < 0) {
+			Py_DECREF(free_value);
+			return 0;
+		}
+        }
+        Py_DECREF(free_value);
+	return 1;
+}   
+
+/* Make final symbol table decisions for block of ste.
+   Arguments:
+   ste -- current symtable entry (input/output)
+   bound -- set of variables bound in enclosing scopes (input)
+   free -- set of free variables in enclosed scopes (output)
+   globals -- set of declared global variables in enclosing scopes (input)
+*/
+
+static int
+analyze_block(PySTEntryObject *ste, PyObject *bound, PyObject *free, 
+	      PyObject *global)
+{
+	PyObject *name, *v, *local = NULL, *scope = NULL, *newbound = NULL;
+	PyObject *newglobal = NULL, *newfree = NULL;
+	int i, flags, pos = 0, success = 0;
+
+	local = PyDict_New();
+	if (!local)
+		goto error;
+	scope = PyDict_New();
+	if (!scope)
+		goto error;
+	newglobal = PyDict_New();
+	if (!newglobal)
+		goto error;
+	newfree = PyDict_New();
+	if (!newfree)
+		goto error;
+	newbound = PyDict_New();
+	if (!newbound)
+		goto error;
+
+	if (ste->ste_type == ClassBlock) {
+		/* make a copy of globals before calling analyze_name(),
+		   because global statements in the class have no effect
+		   on nested functions.
+		*/
+		if (PyDict_Update(newglobal, global) < 0)
+			goto error;
+		if (bound)
+			if (PyDict_Update(newbound, bound) < 0)
+				goto error;
+	}
+
+	assert(PySTEntry_Check(ste));
+	assert(PyDict_Check(ste->ste_symbols));
+	while (PyDict_Next(ste->ste_symbols, &pos, &name, &v)) {
+		flags = PyInt_AS_LONG(v);
+		if (!analyze_name(ste, scope, name, flags, bound, local, free,
+				  global))
+			goto error;
+	}
+
+	if (ste->ste_type != ClassBlock) {
+		if (ste->ste_type == FunctionBlock) {
+			if (PyDict_Update(newbound, local) < 0)
+				goto error;
+		}
+		if (bound) {
+			if (PyDict_Update(newbound, bound) < 0)
+				goto error;
+		}
+		if (PyDict_Update(newglobal, global) < 0)
+			goto error;
+	}
+
+	/* Recursively call analyze_block() on each child block */
+	for (i = 0; i < PyList_GET_SIZE(ste->ste_children); ++i) {
+		PyObject *c = PyList_GET_ITEM(ste->ste_children, i);
+		assert(c && PySTEntry_Check(c));
+		PySTEntryObject* entry = (PySTEntryObject*)c;
+		if (!analyze_block(entry, newbound, newfree, newglobal))
+			goto error;
+		if (entry->ste_free || entry->ste_child_free)
+			ste->ste_child_free = 1;
+	}
+
+	if (ste->ste_type == FunctionBlock && !analyze_cells(scope, newfree))
+		goto error;
+	if (!update_symbols(ste->ste_symbols, scope, bound, newfree,
+			    ste->ste_type == ClassBlock))
+		goto error;
+	if (!check_unoptimized(ste))
+		goto error;
+
+	if (PyDict_Update(free, newfree) < 0)
+		goto error;
+	success = 1;
+ error:
+	Py_XDECREF(local);
+	Py_XDECREF(scope);
+	Py_XDECREF(newbound);
+	Py_XDECREF(newglobal);
+	Py_XDECREF(newfree);
+	if (!success)
+		assert(PyErr_Occurred());
+	return success;
+}
+
+static int
+symtable_analyze(struct symtable *st)
+{
+	PyObject *free, *global;
+	int r;
+
+	free = PyDict_New();
+	if (!free)
+	    return 0;
+	global = PyDict_New();
+	if (!global) {
+	    Py_DECREF(global);
+	    return 0;
+	}
+	r = analyze_block(st->st_top, NULL, free, global);
+	Py_DECREF(free);
+	Py_DECREF(global);
+	return r;
+}
+
+
+static int
+symtable_warn(struct symtable *st, char *msg)
+{
+	if (PyErr_WarnExplicit(PyExc_SyntaxWarning, msg, st->st_filename,
+			       st->st_cur->ste_lineno, NULL, NULL) < 0)	{
+		if (PyErr_ExceptionMatches(PyExc_SyntaxWarning)) {
+			PyErr_SetString(PyExc_SyntaxError, msg);
+			PyErr_SyntaxLocation(st->st_filename, 
+					     st->st_cur->ste_lineno);
+		}
+		return 0;
+	}
+	return 1;
+}
+
+/* symtable_enter_block() gets a reference via PySTEntry_New().
+   This reference is released when the block is exited, via the DECREF
+   in symtable_exit_block().
+*/
+
+static int
+symtable_exit_block(struct symtable *st, void *ast)
+{
+	int end;
+
+	Py_DECREF(st->st_cur);
+	end = PyList_GET_SIZE(st->st_stack) - 1;
+	if (end >= 0) {
+		st->st_cur = (PySTEntryObject *)PyList_GET_ITEM(st->st_stack, 
+								end);
+		Py_INCREF(st->st_cur);
+		if (PySequence_DelItem(st->st_stack, end) < 0)
+			return 0;
+	}
+	return 1;
+}
+
+static int
+symtable_enter_block(struct symtable *st, identifier name, block_ty block, 
+		     void *ast, int lineno)
+{
+	PySTEntryObject *prev = NULL;
+
+	if (st->st_cur) {
+		prev = st->st_cur;
+		if (PyList_Append(st->st_stack, (PyObject *)st->st_cur) < 0) {
+			Py_DECREF(st->st_cur);
+			return 0;
+		}
+		Py_DECREF(st->st_cur);
+	}
+	st->st_cur = PySTEntry_New(st, name, block, ast, lineno);
+	if (name == GET_IDENTIFIER(top))
+		st->st_global = st->st_cur->ste_symbols;
+	if (prev) {
+		if (PyList_Append(prev->ste_children, 
+				  (PyObject *)st->st_cur) < 0) {
+			return 0;
+		}
+	}
+	return 1;
+}
+
+static int
+symtable_lookup(struct symtable *st, PyObject *name)
+{
+	PyObject *o;
+
+	o = PyDict_GetItem(st->st_cur->ste_symbols, name);
+	if (!o)
+		return 0;
+	return PyInt_AsLong(o);
+}
+
+static int
+symtable_add_def(struct symtable *st, PyObject *name, int flag) 
+{
+	PyObject *o;
+	PyObject *dict;
+	int val;
+
+	dict = st->st_cur->ste_symbols;
+	if ((o = PyDict_GetItem(dict, name))) {
+	    val = PyInt_AS_LONG(o);
+	    if ((flag & DEF_PARAM) && (val & DEF_PARAM)) {
+		    PyErr_Format(PyExc_SyntaxError, DUPLICATE_ARGUMENT,
+				 PyString_AsString(name));
+		    PyErr_SyntaxLocation(st->st_filename,
+				       st->st_cur->ste_lineno);
+		    return 0;
+	    }
+	    val |= flag;
+	} else
+	    val = flag;
+	o = PyInt_FromLong(val);
+        if (o == NULL)
+            return 0;
+	if (PyDict_SetItem(dict, name, o) < 0) {
+		Py_DECREF(o);
+		return 0;
+	}
+	Py_DECREF(o);
+
+	if (flag & DEF_PARAM) {
+		if (PyList_Append(st->st_cur->ste_varnames, name) < 0) 
+			return 0;
+	} else	if (flag & DEF_GLOBAL) {
+		/* XXX need to update DEF_GLOBAL for other flags too;
+		   perhaps only DEF_FREE_GLOBAL */
+		val = flag;
+		if ((o = PyDict_GetItem(st->st_global, name))) {
+			val |= PyInt_AS_LONG(o);
+		}
+		o = PyInt_FromLong(val);
+		if (o == NULL)
+			return 0;
+		if (PyDict_SetItem(st->st_global, name, o) < 0) {
+			Py_DECREF(o);
+			return 0;
+		}
+		Py_DECREF(o);
+	}
+	return 1;
+}
+
+/* VISIT, VISIT_SEQ and VIST_SEQ_TAIL take an ASDL type as their second argument.
+   They use the ASDL name to synthesize the name of the C type and the visit
+   function. 
+   
+   VISIT_SEQ_TAIL permits the start of an ASDL sequence to be skipped, which is
+   useful if the first node in the sequence requires special treatment.
+*/
+
+#define VISIT(ST, TYPE, V) \
+	if (!symtable_visit_ ## TYPE((ST), (V))) \
+		return 0; 
+						    
+#define VISIT_SEQ(ST, TYPE, SEQ) { \
+	int i; \
+	asdl_seq *seq = (SEQ); /* avoid variable capture */ \
+	for (i = 0; i < asdl_seq_LEN(seq); i++) { \
+		TYPE ## _ty elt = asdl_seq_GET(seq, i); \
+		if (!symtable_visit_ ## TYPE((ST), elt)) \
+			return 0; \
+	} \
+}
+						    
+#define VISIT_SEQ_TAIL(ST, TYPE, SEQ, START) { \
+	int i; \
+	asdl_seq *seq = (SEQ); /* avoid variable capture */ \
+	for (i = (START); i < asdl_seq_LEN(seq); i++) { \
+		TYPE ## _ty elt = asdl_seq_GET(seq, i); \
+		if (!symtable_visit_ ## TYPE((ST), elt)) \
+			return 0; \
+	} \
+}
+						    
+static int
+symtable_visit_stmt(struct symtable *st, stmt_ty s)
+{
+	switch (s->kind) {
+        case FunctionDef_kind:
+		if (!symtable_add_def(st, s->v.FunctionDef.name, DEF_LOCAL))
+			return 0;
+		if (s->v.FunctionDef.args->defaults)
+			VISIT_SEQ(st, expr, s->v.FunctionDef.args->defaults);
+		if (s->v.FunctionDef.decorators)
+			VISIT_SEQ(st, expr, s->v.FunctionDef.decorators);
+		if (!symtable_enter_block(st, s->v.FunctionDef.name, 
+					  FunctionBlock, (void *)s, s->lineno))
+			return 0;
+		VISIT(st, arguments, s->v.FunctionDef.args);
+		VISIT_SEQ(st, stmt, s->v.FunctionDef.body);
+		if (!symtable_exit_block(st, s))
+			return 0;
+		break;
+        case ClassDef_kind:
+		if (!symtable_add_def(st, s->v.ClassDef.name, DEF_LOCAL))
+			return 0;
+		VISIT_SEQ(st, expr, s->v.ClassDef.bases);
+		if (!symtable_enter_block(st, s->v.ClassDef.name, ClassBlock, 
+					  (void *)s, s->lineno))
+			return 0;
+		VISIT_SEQ(st, stmt, s->v.ClassDef.body);
+		if (!symtable_exit_block(st, s))
+			return 0;
+		break;
+        case Return_kind:
+		if (s->v.Return.value)
+			VISIT(st, expr, s->v.Return.value);
+		break;
+        case Delete_kind:
+		VISIT_SEQ(st, expr, s->v.Delete.targets);
+		break;
+        case Assign_kind:
+		VISIT_SEQ(st, expr, s->v.Assign.targets);
+		VISIT(st, expr, s->v.Assign.value);
+		break;
+        case AugAssign_kind:
+		VISIT(st, expr, s->v.AugAssign.target);
+		VISIT(st, expr, s->v.AugAssign.value);
+		break;
+        case Print_kind:
+		if (s->v.Print.dest)
+			VISIT(st, expr, s->v.Print.dest);
+		VISIT_SEQ(st, expr, s->v.Print.values);
+		break;
+        case For_kind:
+		VISIT(st, expr, s->v.For.target);
+		VISIT(st, expr, s->v.For.iter);
+		VISIT_SEQ(st, stmt, s->v.For.body);
+		if (s->v.For.orelse)
+			VISIT_SEQ(st, stmt, s->v.For.orelse);
+		break;
+        case While_kind:
+		VISIT(st, expr, s->v.While.test);
+		VISIT_SEQ(st, stmt, s->v.While.body);
+		if (s->v.While.orelse)
+			VISIT_SEQ(st, stmt, s->v.While.orelse);
+		break;
+        case If_kind:
+		/* XXX if 0: and lookup_yield() hacks */
+		VISIT(st, expr, s->v.If.test);
+		VISIT_SEQ(st, stmt, s->v.If.body);
+		if (s->v.If.orelse)
+			VISIT_SEQ(st, stmt, s->v.If.orelse);
+		break;
+        case Raise_kind:
+		if (s->v.Raise.type) {
+			VISIT(st, expr, s->v.Raise.type);
+			if (s->v.Raise.inst) {
+				VISIT(st, expr, s->v.Raise.inst);
+				if (s->v.Raise.tback)
+					VISIT(st, expr, s->v.Raise.tback);
+			}
+		}
+		break;
+        case TryExcept_kind:
+		VISIT_SEQ(st, stmt, s->v.TryExcept.body);
+		VISIT_SEQ(st, stmt, s->v.TryExcept.orelse);
+		VISIT_SEQ(st, excepthandler, s->v.TryExcept.handlers);
+		break;
+        case TryFinally_kind:
+		VISIT_SEQ(st, stmt, s->v.TryFinally.body);
+		VISIT_SEQ(st, stmt, s->v.TryFinally.finalbody);
+		break;
+        case Assert_kind:
+		VISIT(st, expr, s->v.Assert.test);
+		if (s->v.Assert.msg)
+			VISIT(st, expr, s->v.Assert.msg);
+		break;
+        case Import_kind:
+		VISIT_SEQ(st, alias, s->v.Import.names);
+		/* XXX Don't have the lineno available inside
+		   visit_alias */
+		if (st->st_cur->ste_unoptimized && !st->st_cur->ste_opt_lineno)
+			st->st_cur->ste_opt_lineno = s->lineno;
+		break;
+        case ImportFrom_kind:
+		VISIT_SEQ(st, alias, s->v.ImportFrom.names);
+		/* XXX Don't have the lineno available inside
+		   visit_alias */
+		if (st->st_cur->ste_unoptimized && !st->st_cur->ste_opt_lineno)
+			st->st_cur->ste_opt_lineno = s->lineno;
+		break;
+        case Exec_kind:
+		VISIT(st, expr, s->v.Exec.body);
+		if (!st->st_cur->ste_opt_lineno)
+			st->st_cur->ste_opt_lineno = s->lineno;
+		if (s->v.Exec.globals) {
+			st->st_cur->ste_unoptimized |= OPT_EXEC;
+			VISIT(st, expr, s->v.Exec.globals);
+			if (s->v.Exec.locals) 
+				VISIT(st, expr, s->v.Exec.locals);
+		} else {
+			st->st_cur->ste_unoptimized |= OPT_BARE_EXEC;
+		}
+		break;
+        case Global_kind: {
+		int i;
+		asdl_seq *seq = s->v.Global.names;
+		for (i = 0; i < asdl_seq_LEN(seq); i++) {
+			identifier name = asdl_seq_GET(seq, i);
+			char *c_name = PyString_AS_STRING(name);
+			int cur = symtable_lookup(st, name);
+			if (cur < 0)
+				return 0;
+			if (cur & (DEF_LOCAL | USE)) {
+				char buf[1000];
+				if (cur & DEF_LOCAL) 
+					PyOS_snprintf(buf, sizeof(buf),
+						      GLOBAL_AFTER_ASSIGN,
+						      c_name);
+				else
+					PyOS_snprintf(buf, sizeof(buf),
+						      GLOBAL_AFTER_USE,
+						      c_name);
+				if (!symtable_warn(st, buf))
+                                    return 0;
+			}
+			if (!symtable_add_def(st, name, DEF_GLOBAL))
+				return 0;
+			
+		}
+		
+		break;
+	}
+        case Expr_kind:
+		VISIT(st, expr, s->v.Expr.value);
+		break;
+        case Pass_kind:
+        case Break_kind:
+        case Continue_kind:
+		/* nothing to do here */
+		break;
+	}
+	return 1;
+}
+
+static int 
+symtable_visit_expr(struct symtable *st, expr_ty e)
+{
+	switch (e->kind) {
+        case BoolOp_kind:
+		VISIT_SEQ(st, expr, e->v.BoolOp.values);
+		break;
+        case BinOp_kind:
+		VISIT(st, expr, e->v.BinOp.left);
+		VISIT(st, expr, e->v.BinOp.right);
+		break;
+        case UnaryOp_kind:
+		VISIT(st, expr, e->v.UnaryOp.operand);
+		break;
+        case Lambda_kind: {
+		if (!symtable_add_def(st, GET_IDENTIFIER(lambda), DEF_LOCAL))
+			return 0;
+		if (e->v.Lambda.args->defaults)
+			VISIT_SEQ(st, expr, e->v.Lambda.args->defaults);
+		/* XXX how to get line numbers for expressions */
+		if (!symtable_enter_block(st, GET_IDENTIFIER(lambda),
+                                          FunctionBlock, (void *)e, 0))
+			return 0;
+		VISIT(st, arguments, e->v.Lambda.args);
+		VISIT(st, expr, e->v.Lambda.body);
+		if (!symtable_exit_block(st, (void *)e))
+			return 0;
+		break;
+	}
+        case Dict_kind:
+		VISIT_SEQ(st, expr, e->v.Dict.keys);
+		VISIT_SEQ(st, expr, e->v.Dict.values);
+		break;
+        case ListComp_kind: {
+		char tmpname[256];
+		identifier tmp;
+
+		PyOS_snprintf(tmpname, sizeof(tmpname), "_[%d]",
+			      ++st->st_cur->ste_tmpname);
+		tmp = PyString_FromString(tmpname);
+		if (!symtable_add_def(st, tmp, DEF_LOCAL))
+			return 0;
+		VISIT(st, expr, e->v.ListComp.elt);
+		VISIT_SEQ(st, comprehension, e->v.ListComp.generators);
+		break;
+	}
+        case GeneratorExp_kind: {
+		if (!symtable_visit_genexp(st, e)) {
+			return 0;
+		}
+		break;
+	}
+        case Yield_kind:
+		if (e->v.Yield.value)
+			VISIT(st, expr, e->v.Yield.value);
+                st->st_cur->ste_generator = 1;
+		break;
+        case Compare_kind:
+		VISIT(st, expr, e->v.Compare.left);
+		VISIT_SEQ(st, expr, e->v.Compare.comparators);
+		break;
+        case Call_kind:
+		VISIT(st, expr, e->v.Call.func);
+		VISIT_SEQ(st, expr, e->v.Call.args);
+		VISIT_SEQ(st, keyword, e->v.Call.keywords);
+		if (e->v.Call.starargs)
+			VISIT(st, expr, e->v.Call.starargs);
+		if (e->v.Call.kwargs)
+			VISIT(st, expr, e->v.Call.kwargs);
+		break;
+        case Repr_kind:
+		VISIT(st, expr, e->v.Repr.value);
+		break;
+        case Num_kind:
+        case Str_kind:
+		/* Nothing to do here. */
+		break;
+	/* The following exprs can be assignment targets. */
+        case Attribute_kind:
+		VISIT(st, expr, e->v.Attribute.value);
+		break;
+        case Subscript_kind:
+		VISIT(st, expr, e->v.Subscript.value);
+		VISIT(st, slice, e->v.Subscript.slice);
+		break;
+        case Name_kind:
+		if (!symtable_add_def(st, e->v.Name.id, 
+				      e->v.Name.ctx == Load ? USE : DEF_LOCAL))
+			return 0;
+		break;
+	/* child nodes of List and Tuple will have expr_context set */
+        case List_kind:
+		VISIT_SEQ(st, expr, e->v.List.elts);
+		break;
+        case Tuple_kind:
+		VISIT_SEQ(st, expr, e->v.Tuple.elts);
+		break;
+	}
+	return 1;
+}
+
+static int
+symtable_implicit_arg(struct symtable *st, int pos)
+{
+	PyObject *id = PyString_FromFormat(".%d", pos);
+	if (id == NULL)
+		return 0;
+	if (!symtable_add_def(st, id, DEF_PARAM)) {
+		Py_DECREF(id);
+		return 0;
+	}
+	Py_DECREF(id);
+	return 1;
+}
+
+static int 
+symtable_visit_params(struct symtable *st, asdl_seq *args, int toplevel)
+{
+	int i, complex = 0;
+	
+        /* go through all the toplevel arguments first */
+	for (i = 0; i < asdl_seq_LEN(args); i++) {
+		expr_ty arg = asdl_seq_GET(args, i);
+		if (arg->kind == Name_kind) {
+			assert(arg->v.Name.ctx == Param ||
+                               (arg->v.Name.ctx == Store && !toplevel));
+			if (!symtable_add_def(st, arg->v.Name.id, DEF_PARAM))
+				return 0;
+		}
+		else if (arg->kind == Tuple_kind) {
+			assert(arg->v.Tuple.ctx == Store);
+                        complex = 1;
+			if (toplevel) {
+				if (!symtable_implicit_arg(st, i))
+					return 0;
+			}
+		}
+		else {
+			/* syntax error */
+			fprintf(stderr, "unexpected expr in parameter list\n");
+			return 0;
+		}
+	}
+
+	if (!toplevel) {
+		if (!symtable_visit_params_nested(st, args))
+			return 0;
+	}
+
+	return 1;
+}
+
+static int
+symtable_visit_params_nested(struct symtable *st, asdl_seq *args)
+{
+	int i;
+	for (i = 0; i < asdl_seq_LEN(args); i++) {
+		expr_ty arg = asdl_seq_GET(args, i);
+		if (arg->kind == Tuple_kind &&
+		    !symtable_visit_params(st, arg->v.Tuple.elts, 0))
+			return 0;
+	}
+	
+	return 1;
+}
+
+static int 
+symtable_visit_arguments(struct symtable *st, arguments_ty a)
+{
+	/* skip default arguments inside function block
+	   XXX should ast be different?
+	*/
+	if (a->args && !symtable_visit_params(st, a->args, 1))
+		return 0;
+	if (a->vararg) {
+		if (!symtable_add_def(st, a->vararg, DEF_PARAM))
+			return 0;
+		st->st_cur->ste_varargs = 1;
+	}
+	if (a->kwarg) {
+		if (!symtable_add_def(st, a->kwarg, DEF_PARAM))
+			return 0;
+		st->st_cur->ste_varkeywords = 1;
+	}
+	if (a->args && !symtable_visit_params_nested(st, a->args))
+		return 0;
+	return 1;
+}
+
+
+static int 
+symtable_visit_excepthandler(struct symtable *st, excepthandler_ty eh)
+{
+	if (eh->type)
+		VISIT(st, expr, eh->type);
+	if (eh->name)
+		VISIT(st, expr, eh->name);
+	VISIT_SEQ(st, stmt, eh->body);
+	return 1;
+}
+
+
+static int 
+symtable_visit_alias(struct symtable *st, alias_ty a)
+{
+	/* Compute store_name, the name actually bound by the import
+	   operation.  It is diferent than a->name when a->name is a
+	   dotted package name (e.g. spam.eggs) 
+	*/
+	PyObject *store_name;
+	PyObject *name = (a->asname == NULL) ? a->name : a->asname;
+	const char *base = PyString_AS_STRING(name);
+	char *dot = strchr(base, '.');
+	if (dot)
+		store_name = PyString_FromStringAndSize(base, dot - base);
+	else {
+		store_name = name;
+		Py_INCREF(store_name);
+	}
+	if (strcmp(PyString_AS_STRING(name), "*")) {
+		int r = symtable_add_def(st, store_name, DEF_IMPORT); 
+		Py_DECREF(store_name);
+		return r;
+	}
+	else {
+            if (st->st_cur->ste_type != ModuleBlock) {
+                if (!symtable_warn(st,
+                                   "import * only allowed at module level"))
+                    return 0;
+            }
+	    st->st_cur->ste_unoptimized |= OPT_IMPORT_STAR;
+	    return 1;
+	}
+}
+
+
+static int 
+symtable_visit_comprehension(struct symtable *st, comprehension_ty lc)
+{
+	VISIT(st, expr, lc->target);
+	VISIT(st, expr, lc->iter);
+	VISIT_SEQ(st, expr, lc->ifs);
+	return 1;
+}
+
+
+static int 
+symtable_visit_keyword(struct symtable *st, keyword_ty k)
+{
+	VISIT(st, expr, k->value);
+	return 1;
+}
+
+
+static int 
+symtable_visit_slice(struct symtable *st, slice_ty s)
+{
+	switch (s->kind) {
+	case Slice_kind:
+		if (s->v.Slice.lower)
+			VISIT(st, expr, s->v.Slice.lower)
+		if (s->v.Slice.upper)
+			VISIT(st, expr, s->v.Slice.upper)
+		if (s->v.Slice.step)
+			VISIT(st, expr, s->v.Slice.step)
+		break;
+	case ExtSlice_kind:
+		VISIT_SEQ(st, slice, s->v.ExtSlice.dims)
+		break;
+	case Index_kind:
+		VISIT(st, expr, s->v.Index.value)
+		break;
+	case Ellipsis_kind:
+		break;
+	}
+	return 1;
+}
+
+static int 
+symtable_visit_genexp(struct symtable *st, expr_ty e)
+{
+	identifier tmp;
+	comprehension_ty outermost = ((comprehension_ty)
+			 (asdl_seq_GET(e->v.GeneratorExp.generators, 0)));
+	/* Outermost iterator is evaluated in current scope */
+	VISIT(st, expr, outermost->iter);
+	/* Create generator scope for the rest */
+	tmp = PyString_FromString("<genexpr>");
+	if (!symtable_enter_block(st, tmp, FunctionBlock, (void *)e, 0)) {
+		return 0;
+	}
+	st->st_cur->ste_generator = 1;
+	/* Outermost iter is received as an argument */
+	if (!symtable_implicit_arg(st, 0)) {
+		return 0;
+	}
+	VISIT(st, expr, outermost->target);
+	VISIT_SEQ(st, expr, outermost->ifs);
+	VISIT_SEQ_TAIL(st, comprehension, e->v.GeneratorExp.generators, 1);
+	VISIT(st, expr, e->v.GeneratorExp.elt);
+	if (!symtable_exit_block(st, (void *)e))
+		return 0;
+	return 1;
+}