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bpo-32836: Remove obsolete code from symtable pass (GH-5680) 

When comprehensions switched to using a nested scope, the old
code for generating a temporary name to hold the accumulation
target became redundant, but was never actually removed.

Patch by Nitish Chandra.
This commit is contained in:
Nitish Chandra 2018-02-27 03:01:20 +05:30 committed by Nick Coghlan
parent 6b5df906af
commit 3a087beddd
3 changed files with 1 additions and 26 deletions
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1
Include/symtable.h
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@ -60,7 +60,6 @@ typedef struct _symtable_entry {
int ste_col_offset; /* offset of first line of block */
int ste_opt_lineno; /* lineno of last exec or import * */
int ste_opt_col_offset; /* offset of last exec or import * */
int ste_tmpname; /* counter for listcomp temp vars */
struct symtable *ste_table;
} PySTEntryObject;

1
Misc/NEWS.d/next/Core and Builtins/2018-02-14-12-35-47.bpo-32836.bThJnx.rst Normal file
View File

@ -0,0 +1 @@
Don't use temporary variables in cases of list/dict/set comprehensions

25
Python/symtable.c
View File

@ -69,7 +69,6 @@ ste_new(struct symtable *st, identifier name, _Py_block_ty block,
ste->ste_varkeywords = 0;
ste->ste_opt_lineno = 0;
ste->ste_opt_col_offset = 0;
ste->ste_tmpname = 0;
ste->ste_lineno = lineno;
ste->ste_col_offset = col_offset;
@ -1082,24 +1081,6 @@ error:
} \
}
static int
symtable_new_tmpname(struct symtable *st)
{
char tmpname[256];
identifier tmp;
PyOS_snprintf(tmpname, sizeof(tmpname), "_[%d]",
++st->st_cur->ste_tmpname);
tmp = PyUnicode_InternFromString(tmpname);
if (!tmp)
return 0;
if (!symtable_add_def(st, tmp, DEF_LOCAL))
return 0;
Py_DECREF(tmp);
return 1;
}
static int
symtable_record_directive(struct symtable *st, identifier name, stmt_ty s)
{
@ -1723,7 +1704,6 @@ symtable_handle_comprehension(struct symtable *st, expr_ty e,
expr_ty elt, expr_ty value)
{
int is_generator = (e->kind == GeneratorExp_kind);
int needs_tmp = !is_generator;
comprehension_ty outermost = ((comprehension_ty)
asdl_seq_GET(generators, 0));
/* Outermost iterator is evaluated in current scope */
@ -1742,11 +1722,6 @@ symtable_handle_comprehension(struct symtable *st, expr_ty e,
symtable_exit_block(st, (void *)e);
return 0;
}
/* Allocate temporary name if needed */
if (needs_tmp && !symtable_new_tmpname(st)) {
symtable_exit_block(st, (void *)e);
return 0;
}
VISIT(st, expr, outermost->target);
VISIT_SEQ(st, expr, outermost->ifs);
VISIT_SEQ_TAIL(st, comprehension, generators, 1);