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Added support for ``if __debug__:'' -- if -O is given, this form is

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recognized by the code generator and code generation for the test and
the subsequent suite is suppressed.

One must write *exactly* ``if __debug__:'' or ``elif __debug__:'' --
no parentheses or operators must be present, or the optimization is
not carried through.  Whitespace doesn't matter.  Other uses of
__debug__ will find __debug__ defined as 0 or 1 in the __builtin__
module.
This commit is contained in:
Guido van Rossum 1997-03-11 18:42:21 +00:00
parent 0824f63cfc
commit 7c53111d5b
1 changed files with 90 additions and 2 deletions
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90
Python/compile.c
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@ -1891,6 +1891,7 @@ com_assign(c, n, assigning)
}
}
}
/* Forward */ static node *get_rawdocstring PROTO((node *));
static void
@ -2170,6 +2171,90 @@ com_exec_stmt(c, n)
com_pop(c, 3);
}
static int
is_constant_false(c, n)
struct compiling *c;
node *n;
{
object *v;
int i;
/* Label to avoid tail recursion */
next:
switch (TYPE(n)) {
case suite:
if (NCH(n) == 1) {
n = CHILD(n, 0);
goto next;
}
/* Fall through */
case file_input:
for (i = 0; i < NCH(n); i++) {
node *ch = CHILD(n, i);
if (TYPE(ch) == stmt) {
n = ch;
goto next;
}
}
break;
case stmt:
case simple_stmt:
case small_stmt:
n = CHILD(n, 0);
goto next;
case expr_stmt:
case testlist:
case test:
case and_test:
case not_test:
case comparison:
case expr:
case xor_expr:
case and_expr:
case shift_expr:
case arith_expr:
case term:
case factor:
case power:
case atom:
if (NCH(n) == 1) {
n = CHILD(n, 0);
goto next;
}
break;
case NAME:
if (Py_OptimizeFlag && strcmp(STR(n), "__debug__") == 0)
return 1;
break;
case NUMBER:
v = parsenumber(c, STR(n));
if (v == NULL) {
err_clear();
break;
}
i = testbool(v);
DECREF(v);
return i == 0;
case STRING:
v = parsestrplus(n);
if (v == NULL) {
err_clear();
break;
}
i = testbool(v);
DECREF(v);
return i == 0;
}
return 0;
}
static void
com_if_stmt(c, n)
struct compiling *c;
@ -2182,9 +2267,11 @@ com_if_stmt(c, n)
for (i = 0; i+3 < NCH(n); i+=4) {
int a = 0;
node *ch = CHILD(n, i+1);
if (is_constant_false(c, ch))
continue;
if (i > 0)
com_addoparg(c, SET_LINENO, ch->n_lineno);
com_node(c, CHILD(n, i+1));
com_node(c, ch);
com_addfwref(c, JUMP_IF_FALSE, &a);
com_addbyte(c, POP_TOP);
com_pop(c, 1);
@ -2196,6 +2283,7 @@ com_if_stmt(c, n)
}
if (i+2 < NCH(n))
com_node(c, CHILD(n, i+2));
if (anchor)
com_backpatch(c, anchor);
}