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com_print_stmt(): Guido rightly points out that the stream expression 

in extended prints should only be evaluated once.  This patch plays
stack games (documented!) to fix this.
This commit is contained in:
Barry Warsaw 2000-08-21 17:07:20 +00:00
parent 62c53ddabe
commit 24703a02e7
1 changed files with 22 additions and 5 deletions
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27
Python/compile.c
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@ -2055,6 +2055,9 @@ com_print_stmt(struct compiling *c, node *n)
/* are we using the extended print form? */
if (NCH(n) >= 2 && TYPE(CHILD(n, 1)) == RIGHTSHIFT) {
stream = CHILD(n, 2);
com_node(c, stream);
/* stack: [...] => [... stream] */
com_push(c, 1);
if (NCH(n) > 3 && TYPE(CHILD(n, 3)) == COMMA)
i = 4;
else
@ -2062,24 +2065,38 @@ com_print_stmt(struct compiling *c, node *n)
}
for (; i < NCH(n); i += 2) {
if (stream != NULL) {
/* stack: [...] => [... obj stream] */
com_addbyte(c, DUP_TOP);
/* stack: [stream] => [stream stream] */
com_push(c, 1);
com_node(c, CHILD(n, i));
com_node(c, stream);
/* stack: [stream stream] => [stream stream obj] */
com_addbyte(c, ROT_TWO);
/* stack: [stream stream obj] => [stream obj stream] */
com_addbyte(c, PRINT_ITEM_TO);
/* stack: [stream obj stream] => [stream] */
com_pop(c, 2);
}
else {
/* stack: [...] => [... obj] */
com_node(c, CHILD(n, i));
/* stack: [...] => [... obj] */
com_addbyte(c, PRINT_ITEM);
com_pop(c, 1);
}
}
/* XXX Alternatively, LOAD_CONST '\n' and then PRINT_ITEM */
if (TYPE(CHILD(n, NCH(n)-1)) != COMMA) {
if (TYPE(CHILD(n, NCH(n)-1)) == COMMA) {
if (stream != NULL) {
com_node(c, stream);
/* must pop the extra stream object off the stack */
com_addbyte(c, POP_TOP);
/* stack: [... stream] => [...] */
com_pop(c, 1);
}
}
else {
if (stream != NULL) {
/* this consumes the last stream object on stack */
com_addbyte(c, PRINT_NEWLINE_TO);
/* stack: [... stream] => [...] */
com_pop(c, 1);
}
else