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 <[email protected]> --- Changes in v4: - Newly added Changes in v3: None Changes in v2: None scripts/kconfig/preprocess.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c index c39e30e..246f879 100644 --- a/scripts/kconfig/preprocess.c +++ b/scripts/kconfig/preprocess.c @@ -276,6 +276,7 @@ struct variable { char *name; char *value; enum variable_flavor flavor; + int exp_count; struct list_head node; }; @@ -306,8 +307,19 @@ static char *variable_expand(const char *name, int argc, char *argv[], expanded_argv[i] = expand_string_with_args(argv[i], old_argc, old_argv); + 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++; + res = expand_string_with_args(v->value, argc, expanded_argv); + v->exp_count--; + for (i = 0; i < argc; i++) free(expanded_argv[i]); @@ -337,6 +349,7 @@ 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); } -- 2.7.4
