kconfig: print more info when we see a recursive dependency

Consider following kconfig file:

config TEST1
	bool "test 1"
	depends on TEST2

config TEST2
	bool "test 2"
	depends on TEST1

Previously kconfig would report:

foo:6:error: found recursive dependency: TEST2 -> TEST1 -> TEST2

With the following patch kconfig reports:
foo:5:error: recursive dependency detected!
foo:5:  symbol TEST2 depends on TEST1
foo:1:  symbol TEST1 depends on TEST2

Note that we now report where the offending symbols are defined.
This can be a great help for complex situations involving
several files.

Patch is originally from Roman Zippel with a few adjustments by Sam.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

1 files changed, 127 insertions, 15 deletions

diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 9f180ab7698d..bc1e1584e2da 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -783,6 +783,110 @@ struct symbol **sym_re_search(const char *pattern)
         return sym_arr;
 }
 
+/*
+ * When we check for recursive dependencies we use a stack to save
+ * current state so we can print out relevant info to user.
+ * The entries are located on the call stack so no need to free memory.
+ * Note inser() remove() must always match to properly clear the stack.
+ */
+static struct dep_stack {
+        struct dep_stack *prev, *next;
+        struct symbol *sym;
+        struct property *prop;
+        struct expr *expr;
+} *check_top;
+
+static void dep_stack_insert(struct dep_stack *stack, struct symbol *sym)
+{
+        memset(stack, 0, sizeof(*stack));
+        if (check_top)
+                check_top->next = stack;
+        stack->prev = check_top;
+        stack->sym = sym;
+        check_top = stack;
+}
+
+static void dep_stack_remove(void)
+{
+        check_top = check_top->prev;
+        if (check_top)
+                check_top->next = NULL;
+}
+
+/*
+ * Called when we have detected a recursive dependency.
+ * check_top point to the top of the stact so we use
+ * the ->prev pointer to locate the bottom of the stack.
+ */
+static void sym_check_print_recursive(struct symbol *last_sym)
+{
+        struct dep_stack *stack;
+        struct symbol *sym, *next_sym;
+        struct menu *menu = NULL;
+        struct property *prop;
+        struct dep_stack cv_stack;
+
+        if (sym_is_choice_value(last_sym)) {
+                dep_stack_insert(&cv_stack, last_sym);
+                last_sym = prop_get_symbol(sym_get_choice_prop(last_sym));
+        }
+
+        for (stack = check_top; stack != NULL; stack = stack->prev)
+                if (stack->sym == last_sym)
+                        break;
+        if (!stack) {
+                fprintf(stderr, "unexpected recursive dependency error\n");
+                return;
+        }
+
+        for (; stack; stack = stack->next) {
+                sym = stack->sym;
+                next_sym = stack->next ? stack->next->sym : last_sym;
+                prop = stack->prop;
+
+                /* for choice values find the menu entry (used below) */
+                if (sym_is_choice(sym) || sym_is_choice_value(sym)) {
+                        for (prop = sym->prop; prop; prop = prop->next) {
+                                menu = prop->menu;
+                                if (prop->menu)
+                                        break;
+                        }
+                }
+                if (stack->sym == last_sym)
+                        fprintf(stderr, "%s:%d:error: recursive dependency detected!\n",
+                                prop->file->name, prop->lineno);
+                if (stack->expr) {
+                        fprintf(stderr, "%s:%d:\tsymbol %s %s value contains %s\n",
+                                prop->file->name, prop->lineno,
+                                sym->name ? sym->name : "<choice>",
+                                prop_get_type_name(prop->type),
+                                next_sym->name ? next_sym->name : "<choice>");
+                } else if (stack->prop) {
+                        fprintf(stderr, "%s:%d:\tsymbol %s depends on %s\n",
+                                prop->file->name, prop->lineno,
+                                sym->name ? sym->name : "<choice>",
+                                next_sym->name ? next_sym->name : "<choice>");
+                } else if (sym_is_choice(sym)) {
+                        fprintf(stderr, "%s:%d:\tchoice %s contains symbol %s\n",
+                                menu->file->name, menu->lineno,
+                                sym->name ? sym->name : "<choice>",
+                                next_sym->name ? next_sym->name : "<choice>");
+                } else if (sym_is_choice_value(sym)) {
+                        fprintf(stderr, "%s:%d:\tsymbol %s is part of choice %s\n",
+                                menu->file->name, menu->lineno,
+                                sym->name ? sym->name : "<choice>",
+                                next_sym->name ? next_sym->name : "<choice>");
+                } else {
+                        fprintf(stderr, "%s:%d:\tsymbol %s is selected by %s\n",
+                                prop->file->name, prop->lineno,
+                                sym->name ? sym->name : "<choice>",
+                                next_sym->name ? next_sym->name : "<choice>");
+                }
+        }
+
+        if (check_top == &cv_stack)
+                dep_stack_remove();
+}
 
 static struct symbol *sym_check_expr_deps(struct expr *e)
 {
@@ -819,24 +923,33 @@ static struct symbol *sym_check_sym_deps(struct symbol *sym)
 {
         struct symbol *sym2;
         struct property *prop;
+        struct dep_stack stack;
+
+        dep_stack_insert(&stack, sym);
 
         sym2 = sym_check_expr_deps(sym->rev_dep.expr);
         if (sym2)
-                return sym2;
+                goto out;
 
         for (prop = sym->prop; prop; prop = prop->next) {
                 if (prop->type == P_CHOICE || prop->type == P_SELECT)
                         continue;
+                stack.prop = prop;
                 sym2 = sym_check_expr_deps(prop->visible.expr);
                 if (sym2)
                         break;
                 if (prop->type != P_DEFAULT || sym_is_choice(sym))
                         continue;
+                stack.expr = prop->expr;
                 sym2 = sym_check_expr_deps(prop->expr);
                 if (sym2)
                         break;
+                stack.expr = NULL;
         }
 
+out:
+        dep_stack_remove();
+
         return sym2;
 }
 
@@ -845,6 +958,9 @@ static struct symbol *sym_check_choice_deps(struct symbol *choice)
         struct symbol *sym, *sym2;
         struct property *prop;
         struct expr *e;
+        struct dep_stack stack;
+
+        dep_stack_insert(&stack, choice);
 
         prop = sym_get_choice_prop(choice);
         expr_list_for_each_sym(prop->expr, e, sym)
@@ -858,10 +974,8 @@ static struct symbol *sym_check_choice_deps(struct symbol *choice)
 
         expr_list_for_each_sym(prop->expr, e, sym) {
                 sym2 = sym_check_sym_deps(sym);
-                if (sym2) {
-                        fprintf(stderr, " -> %s", sym->name);
+                if (sym2)
                         break;
-                }
         }
 out:
         expr_list_for_each_sym(prop->expr, e, sym)
@@ -871,6 +985,8 @@ out:
             prop_get_symbol(sym_get_choice_prop(sym2)) == choice)
                 sym2 = choice;
 
+        dep_stack_remove();
+
         return sym2;
 }
 
@@ -880,18 +996,20 @@ struct symbol *sym_check_deps(struct symbol *sym)
         struct property *prop;
 
         if (sym->flags & SYMBOL_CHECK) {
-                fprintf(stderr, "%s:%d:error: found recursive dependency: %s",
-                        sym->prop->file->name, sym->prop->lineno,
-                        sym->name ? sym->name : "<choice>");
+                sym_check_print_recursive(sym);
                 return sym;
         }
         if (sym->flags & SYMBOL_CHECKED)
                 return NULL;
 
         if (sym_is_choice_value(sym)) {
+                struct dep_stack stack;
+
                 /* for choice groups start the check with main choice symbol */
+                dep_stack_insert(&stack, sym);
                 prop = sym_get_choice_prop(sym);
                 sym2 = sym_check_deps(prop_get_symbol(prop));
+                dep_stack_remove();
         } else if (sym_is_choice(sym)) {
                 sym2 = sym_check_choice_deps(sym);
         } else {
@@ -900,14 +1018,8 @@ struct symbol *sym_check_deps(struct symbol *sym)
                 sym->flags &= ~SYMBOL_CHECK;
         }
 
-        if (sym2) {
-                fprintf(stderr, " -> %s", sym->name ? sym->name : "<choice>");
-                if (sym2 == sym) {
-                        fprintf(stderr, "\n");
-                        zconfnerrs++;
-                        sym2 = NULL;
-                }
-        }
+        if (sym2 && sym2 == sym)
+                sym2 = NULL;
 
         return sym2;
 }