kconfig: error out if a recursive variable references itself (915f6490) · Commits · e / devices / android_kernel_oneplus_sm7250

When using a recursively expanded variable, it is a common mistake to make circular reference. For example, Make terminates the following code: X = $(X) Y := $(X) Let's detect the circular expansion in Kconfig, too. On the other hand, a function that recurses itself is a commonly-used programming technique. So, Make does not check recursion in the reference with 'call'. For example, the following code continues running eternally: X = $(call X) Y := $(X) Kconfig allows circular expansion if one or more arguments are given, but terminates when the same function is recursively invoked 1000 times, assuming it is a programming mistake. Signed-off-by:

Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/kconfig/preprocess.c

+13 −0

Original line number	Diff line number	Diff line
		@@ -229,6 +229,7 @@ struct variable {
		char *name;
		char *value;
		enum variable_flavor flavor;
		int exp_count;
		struct list_head node;
		};

		@@ -253,11 +254,22 @@ static char variable_expand(const char name, int argc, char *argv[])
		if (!v)
		return NULL;

		if (argc == 0 && v->exp_count)
		pperror("Recursive variable '%s' references itself (eventually)",
		name);

		if (v->exp_count > 1000)
		pperror("Too deep recursive expansion");

		v->exp_count++;

		if (v->flavor == VAR_RECURSIVE)
		res = expand_string_with_args(v->value, argc, argv);
		else
		res = xstrdup(v->value);

		v->exp_count--;

		return res;
		}

		@@ -284,6 +296,7 @@ void variable_add(const char name, const char value,

		v = xmalloc(sizeof(*v));
		v->name = xstrdup(name);
		v->exp_count = 0;
		list_add_tail(&v->node, &variable_list);
		}