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Add a comment explaining the st_symbols cache.

This commit is contained in:
Jeremy Hylton 2001-12-10 00:53:18 +00:00
parent 5801a2d8e3
commit 2990640d8a
1 changed files with 15 additions and 1 deletions
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16
Python/symtable.c
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@ -4,6 +4,20 @@
#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.
*/
PyObject *
PySymtableEntry_New(struct symtable *st, char *name, int type, int lineno)
{
@ -14,7 +28,7 @@ PySymtableEntry_New(struct symtable *st, char *name, int type, int lineno)
if (k == NULL)
goto fail;
v = PyDict_GetItem(st->st_symbols, k);
if (v) /* XXX could check that name, type, lineno match */ {
if (v) {
Py_DECREF(k);
Py_INCREF(v);
return v;