[PATCH] kconfig: fix extra output from savedefconfig on out-of-range defaults

[Julian Braha <julianbraha@gmail.com>]

The Kconfig interpreter currently allows defaults that are outside of the
range bounds.

In these cases, the 'sym_validate_range' function will adjust the default
value to the nearest range bound. For example, see this example:

  config A
    int
    range 1 2
    default 16

Here, since the default value of 16 is greater than the bounds, the
effective default value gets adjusted down to the upper bound, 2.

However, 'savedefconfig' writes non-default values, and without being
aware of the automatic adjustment to the range bound, it would write: A=2

This limitation is also documented in a comment: "The following fails to
handle the situation where a default value is further limited by the valid
range."

To resolve this, let's factor out the default-range adjustment logic from
the existing 'sym_validate_range' function into its own
'sym_get_near_range_bound' function for 'savedefconfig' to use too, so
that it compares against the effective value.

Adds tests, accordingly.

Fixes: 7cf3d73b4360 ("kconfig: add savedefconfig")
Assisted-by: Codex:gpt-5.6-sol
Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Closes: https://lore.kernel.org/lkml/CAMuHMdVyUAA3L4mUkSjmnuE3cvj-+N8z-Bhxsh1wa-FQWc=fjw@mail.gmail.com/
Signed-off-by: Julian Braha <julianbraha@gmail.com>
---
 scripts/kconfig/symbol.c                      | 39 ++++++++----
 .../kconfig/tests/savedefconfig_range/Kconfig | 60 +++++++++++++++++++
 .../tests/savedefconfig_range/__init__.py     |  8 +++
 .../kconfig/tests/savedefconfig_range/config  |  7 +++
 .../savedefconfig_range/expected_defconfig    |  0
 5 files changed, 102 insertions(+), 12 deletions(-)
 create mode 100644 scripts/kconfig/tests/savedefconfig_range/Kconfig
 create mode 100644 scripts/kconfig/tests/savedefconfig_range/__init__.py
 create mode 100644 scripts/kconfig/tests/savedefconfig_range/config
 create mode 100644 scripts/kconfig/tests/savedefconfig_range/expected_defconfig

diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 2d1c021fa395..72aaae9da4b1 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -158,7 +158,12 @@ static long long sym_get_range_val(struct symbol *sym, int base)
 	return strtoll(sym->curr.val, NULL, base);
 }
 
-static void sym_validate_range(struct symbol *sym)
+/*
+ * Return the nearest range bound for an out-of-range default value.
+ * Return NULL if the value is valid or the symbol has no active range.
+ */
+static struct symbol *sym_get_near_range_bound(struct symbol *sym,
+					  const char *value)
 {
 	struct property *prop;
 	struct symbol *range_sym;
@@ -173,21 +178,31 @@ static void sym_validate_range(struct symbol *sym)
 		base = 16;
 		break;
 	default:
-		return;
+		return NULL;
 	}
 	prop = sym_get_range_prop(sym);
 	if (!prop)
-		return;
-	val = strtoll(sym->curr.val, NULL, base);
+		return NULL;
+	val = strtoll(value, NULL, base);
 	range_sym = prop->expr->left.sym;
 	val2 = sym_get_range_val(range_sym, base);
 	if (val >= val2) {
 		range_sym = prop->expr->right.sym;
 		val2 = sym_get_range_val(range_sym, base);
 		if (val <= val2)
-			return;
+			return NULL;
 	}
-	sym->curr.val = range_sym->curr.val;
+
+	return range_sym;
+}
+
+static void sym_validate_range(struct symbol *sym)
+{
+	struct symbol *range_sym;
+
+	range_sym = sym_get_near_range_bound(sym, sym->curr.val);
+	if (range_sym)
+		sym->curr.val = range_sym->curr.val;
 }
 
 static void sym_set_changed(struct symbol *sym)
@@ -832,7 +847,7 @@ bool sym_set_string_value(struct symbol *sym, const char *newval)
 const char *sym_get_string_default(struct symbol *sym)
 {
 	struct property *prop;
-	struct symbol *ds;
+	struct symbol *ds, *range_sym;
 	const char *str = "";
 	tristate val;
 
@@ -850,11 +865,6 @@ const char *sym_get_string_default(struct symbol *sym)
 			val = EXPR_AND(expr_calc_value(prop->expr), prop->visible.tri);
 			break;
 		default:
-			/*
-			 * The following fails to handle the situation
-			 * where a default value is further limited by
-			 * the valid range.
-			 */
 			ds = prop_get_symbol(prop);
 			if (ds != NULL) {
 				sym_calc_value(ds);
@@ -898,6 +908,11 @@ const char *sym_get_string_default(struct symbol *sym)
 	default:
 		break;
 	}
+
+	range_sym = sym_get_near_range_bound(sym, str);
+	if (range_sym)
+		str = range_sym->curr.val;
+
 	return str;
 }
 
diff --git a/scripts/kconfig/tests/savedefconfig_range/Kconfig b/scripts/kconfig/tests/savedefconfig_range/Kconfig
new file mode 100644
index 000000000000..fd59d9082ed5
--- /dev/null
+++ b/scripts/kconfig/tests/savedefconfig_range/Kconfig
@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# Static default and range values
+
+config INT_DEFAULT_ABOVE_RANGE
+	int
+	range 1 1
+	default 16
+
+config INT_DEFAULT_BELOW_RANGE
+	int
+	range 4 8
+	default 2
+
+# Default and range values determined by other options
+
+config RANGE_UPPER_BOUND
+	int
+	default 3
+
+config INT_DYNAMIC_RANGE
+	int
+	range 0 RANGE_UPPER_BOUND
+	default 4
+
+# Hex
+
+config HEX_DEFAULT_ABOVE_RANGE
+	hex
+	range 0x10 0x20
+	default 0x40
+
+# Implicit default value of 0
+
+config INT_IMPLICIT_DEFAULT_ZERO
+	int
+	range 1 4
+
+# Conditional range
+
+config USE_FIRST_RANGE
+	bool
+	default y
+
+config INT_CONDITIONAL_RANGE
+	int
+	range 1 2 if USE_FIRST_RANGE
+	range 3 4 if !USE_FIRST_RANGE
+	default 3
+
+# Conditional default
+
+config USE_DEFAULT
+	bool
+	default y
+
+config INT_CONDITIONAL_DEFAULT
+	int
+	range 1 2
+	default 3 if USE_DEFAULT
diff --git a/scripts/kconfig/tests/savedefconfig_range/__init__.py b/scripts/kconfig/tests/savedefconfig_range/__init__.py
new file mode 100644
index 000000000000..961454be732c
--- /dev/null
+++ b/scripts/kconfig/tests/savedefconfig_range/__init__.py
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+"""Test savedefconfig with numerical defaults outside of ranges."""
+
+
+def test(conf):
+    assert conf._run_conf('--savedefconfig=defconfig', dot_config='config',
+                          out_file='defconfig') == 0
+    assert conf.config_matches('expected_defconfig')
diff --git a/scripts/kconfig/tests/savedefconfig_range/config b/scripts/kconfig/tests/savedefconfig_range/config
new file mode 100644
index 000000000000..d939cfe5fd34
--- /dev/null
+++ b/scripts/kconfig/tests/savedefconfig_range/config
@@ -0,0 +1,7 @@
+CONFIG_INT_DEFAULT_ABOVE_RANGE=1
+CONFIG_INT_DEFAULT_BELOW_RANGE=4
+CONFIG_INT_DYNAMIC_RANGE=3
+CONFIG_HEX_DEFAULT_ABOVE_RANGE=0x20
+CONFIG_INT_IMPLICIT_DEFAULT_ZERO=1
+CONFIG_INT_CONDITIONAL_RANGE=2
+CONFIG_INT_CONDITIONAL_DEFAULT=2
diff --git a/scripts/kconfig/tests/savedefconfig_range/expected_defconfig b/scripts/kconfig/tests/savedefconfig_range/expected_defconfig
new file mode 100644
index 000000000000..e69de29bb2d1
-- 
2.55.0