Currently, comparisons to 'm' or 'n' result in incorrect output.
[Test Code]
config MODULES
def_bool y
modules
config A
def_tristate m
config B
def_bool A > n
CONFIG_B is actually unset, while the expectation is CONFIG_B=y.
The reason for the issue is because Kconfig compares the tristate values
as strings.
Currently, the .type fields of the constant symbols, 'y', 'm', and 'n'
are unspecified, i.e., S_UNKNOWN.
When expr_calc_value() evaluates 'A > n', it checks the types of 'A' and
'n' to determine how to compare them.
The left-hand side, 'A', is a tristate symbol with a value of 'm', which
corresponds to a numeric value of 1. (Internally, 'y', 'm', and 'n' are
represented as 2, 1, and 0, respectively.)
The right-hand side, 'n', has an unknown type, so it is treated as the
string "n" during the comparison.
expr_calc_value() compares two values numerically only when both can
have numeric values. Otherwise, they are compared as strings.
symbol numeric value ASCII code
-------------------------------------
y 2 0x79
m 1 0x6d
n 0 0x6e
'm' is greater than 'n' if compared numerically (since 1 is greater
than 0), but small than 'n' if compared as strings (since the ASCII
code 0x6d is smaller than 0x6e).
Specifying .type=S_TRISTATE for symbol_{yes,mod,no} fixes the above
test code.
However, this would cause a regression to the following test code.
[Test Code 2]
config MODULES
def_bool n
modules
config A
def_tristate n
config B
def_bool A = m
You would get CONFIG_B=y, while CONFIG_B should not be set.
The reason is because sym_get_string_value() turns 'm' into 'n' when
the module feature is disabled. Consequently, expr_calc_value() returns
the result of 'A = n' instead of 'A = m'. This oddity has been hidden
because the type of 'm' was previously S_UNKNOWN instead of S_TRISTATE.
sym_get_string_value() should not tweak the string because the tristate
value has already been correctly calculated. There is no reason to
return the string "n" where its tristate value is mod.
Signed-off-by: Masahiro Yamada <[email protected]>
---
scripts/kconfig/symbol.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index aa0e25ee5119..0e439d3d48d1 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -14,6 +14,7 @@
struct symbol symbol_yes = {
.name = "y",
+ .type = S_TRISTATE,
.curr = { "y", yes },
.menus = LIST_HEAD_INIT(symbol_yes.menus),
.flags = SYMBOL_CONST|SYMBOL_VALID,
@@ -21,6 +22,7 @@ struct symbol symbol_yes = {
struct symbol symbol_mod = {
.name = "m",
+ .type = S_TRISTATE,
.curr = { "m", mod },
.menus = LIST_HEAD_INIT(symbol_mod.menus),
.flags = SYMBOL_CONST|SYMBOL_VALID,
@@ -28,6 +30,7 @@ struct symbol symbol_mod = {
struct symbol symbol_no = {
.name = "n",
+ .type = S_TRISTATE,
.curr = { "n", no },
.menus = LIST_HEAD_INIT(symbol_no.menus),
.flags = SYMBOL_CONST|SYMBOL_VALID,
@@ -820,8 +823,7 @@ const char *sym_get_string_value(struct symbol *sym)
case no:
return "n";
case mod:
- sym_calc_value(modules_sym);
- return (modules_sym->curr.tri == no) ? "n" : "m";
+ return "m";
case yes:
return "y";
}
--
2.40.1
On Sun, May 19, 2024 at 6:22 PM Masahiro Yamada <[email protected]> wrote:
>
> Currently, comparisons to 'm' or 'n' result in incorrect output.
>
> [Test Code]
>
> config MODULES
> def_bool y
> modules
>
> config A
> def_tristate m
>
> config B
> def_bool A > n
>
> CONFIG_B is actually unset, while the expectation is CONFIG_B=y.
>
> The reason for the issue is because Kconfig compares the tristate values
> as strings.
>
> Currently, the .type fields of the constant symbols, 'y', 'm', and 'n'
> are unspecified, i.e., S_UNKNOWN.
>
> When expr_calc_value() evaluates 'A > n', it checks the types of 'A' and
> 'n' to determine how to compare them.
>
> The left-hand side, 'A', is a tristate symbol with a value of 'm', which
> corresponds to a numeric value of 1. (Internally, 'y', 'm', and 'n' are
> represented as 2, 1, and 0, respectively.)
>
> The right-hand side, 'n', has an unknown type, so it is treated as the
> string "n" during the comparison.
>
> expr_calc_value() compares two values numerically only when both can
> have numeric values. Otherwise, they are compared as strings.
>
> symbol numeric value ASCII code
> -------------------------------------
> y 2 0x79
> m 1 0x6d
> n 0 0x6e
>
> 'm' is greater than 'n' if compared numerically (since 1 is greater
> than 0), but small than 'n' if compared as strings (since the ASCII
> code 0x6d is smaller than 0x6e).
>
> Specifying .type=S_TRISTATE for symbol_{yes,mod,no} fixes the above
> test code.
>
> However, this would cause a regression to the following test code.
>
> [Test Code 2]
>
> config MODULES
> def_bool n
> modules
>
> config A
> def_tristate n
>
> config B
> def_bool A = m
>
> You would get CONFIG_B=y, while CONFIG_B should not be set.
>
> The reason is because sym_get_string_value() turns 'm' into 'n' when
> the module feature is disabled. Consequently, expr_calc_value() returns
> the result of 'A = n' instead of 'A = m'. This oddity has been hidden
> because the type of 'm' was previously S_UNKNOWN instead of S_TRISTATE.
>
> sym_get_string_value() should not tweak the string because the tristate
> value has already been correctly calculated. There is no reason to
> return the string "n" where its tristate value is mod.
>
> Signed-off-by: Masahiro Yamada <[email protected]>
> ---
Fixes: 31847b67bec0 ("kconfig: allow use of relations other than (in)equality")
--
Best Regards
Masahiro Yamada
On Sun, May 19, 2024 at 6:22 PM Masahiro Yamada <[email protected]> wrote:
>
> Currently, comparisons to 'm' or 'n' result in incorrect output.
>
> [Test Code]
>
> config MODULES
> def_bool y
> modules
>
> config A
> def_tristate m
>
> config B
> def_bool A > n
>
> CONFIG_B is actually unset, while the expectation is CONFIG_B=y.
>
> The reason for the issue is because Kconfig compares the tristate values
> as strings.
>
> Currently, the .type fields of the constant symbols, 'y', 'm', and 'n'
> are unspecified, i.e., S_UNKNOWN.
>
> When expr_calc_value() evaluates 'A > n', it checks the types of 'A' and
> 'n' to determine how to compare them.
>
> The left-hand side, 'A', is a tristate symbol with a value of 'm', which
> corresponds to a numeric value of 1. (Internally, 'y', 'm', and 'n' are
> represented as 2, 1, and 0, respectively.)
>
> The right-hand side, 'n', has an unknown type, so it is treated as the
> string "n" during the comparison.
>
> expr_calc_value() compares two values numerically only when both can
> have numeric values. Otherwise, they are compared as strings.
>
> symbol numeric value ASCII code
> -------------------------------------
> y 2 0x79
> m 1 0x6d
> n 0 0x6e
>
> 'm' is greater than 'n' if compared numerically (since 1 is greater
> than 0), but small than 'n' if compared as strings (since the ASCII
small than -> smaller than
--
Best Regards
Masahiro Yamada