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kconfig/menu.c: fix multiple references to expressions in menu_add_prop()

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menu_add_prop() applies upper menus' visibilities to actual prompts
by AND-ing the prompts visibilities with the upper menus ones.

This creates a further reference to the menu's visibilities and when
the expression reduction functions do their work, they may remove or
modify expressions that have multiple references, thus causing
unpredictable side-effects.

The following example Kconfig constructs a case where this causes
problems: a menu and a prompt which's visibilities depend on the same
symbol.  When invoking mconf with this Kconfig and pressing "Z" we
see a problem caused by a free'd expression still referenced by the
menu's visibility:

------------------------------------------------------------------------
mainmenu "Kconfig Testing Configuration"

config VISIBLE
	def_bool n

config Placeholder
	bool "Place holder"

menu "Invisible"
	visible if VISIBLE

config TEST_VAR
	bool "Test option" if VISIBLE

endmenu
------------------------------------------------------------------------

This patch fixes this problem by creating copies of the menu's
visibility expressions before AND-ing them with the prompt's one.

Signed-off-by: Dirk Gouders <dirk@gouders.net>
[yann.morin.1998@free.fr: move variable into its block-scope,
                          keep lines <80 chars, typo]
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
This commit is contained in:
Dirk Gouders 2013-05-21 10:54:11 +02:00 committed by Yann E. MORIN
parent 063f4661fd
commit e983b7b17a
1 changed files with 14 additions and 1 deletions
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15
scripts/kconfig/menu.c
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@ -146,11 +146,24 @@ struct property *menu_add_prop(enum prop_type type, char *prompt, struct expr *e
struct menu *menu = current_entry;
while ((menu = menu->parent) != NULL) {
struct expr *dup_expr;
if (!menu->visibility)
continue;
/*
* Do not add a reference to the
* menu's visibility expression but
* use a copy of it. Otherwise the
* expression reduction functions
* will modify expressions that have
* multiple references which can
* cause unwanted side effects.
*/
dup_expr = expr_copy(menu->visibility);
prop->visible.expr
= expr_alloc_and(prop->visible.expr,
menu->visibility);
dup_expr);
}
}