Commit 5e8c5299 authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

kconfig: report recursive dependency involving 'imply' 



Currently, Kconfig does not complain about the recursive dependency
where 'imply' keywords are involved.

[Test Code]

  config A
          bool "a"

  config B
          bool "b"
          imply A
          depends on A

In the code above, Kconfig cannot calculate the symbol values correctly
due to the circular dependency.  For example, allyesconfig followed by
syncconfig results in an odd behavior because CONFIG_B becomes visible
in syncconfig.

  $ make allyesconfig
  scripts/kconfig/conf  --allyesconfig Kconfig
  #
  # configuration written to .config
  #
  $ cat .config
  #
  # Automatically generated file; DO NOT EDIT.
  # Main menu
  #
  CONFIG_A=y
  $ make syncconfig
  scripts/kconfig/conf  --syncconfig Kconfig
  *
  * Restart config...
  *
  *
  * Main menu
  *
  a (A) [Y/n/?] y
    b (B) [N/y/?] (NEW)

To detect this correctly, sym_check_expr_deps() should recurse to
not only sym->rev_dep.expr but also sym->implied.expr .

At this moment, sym_check_print_recursive() cannot distinguish
'select' and 'imply' since it does not know the precise context
where the recursive dependency has been hit.  This will be solved
by the next commit.

In fact, even the document and the unit-test are confused.  Using
'imply' does not solve recursive dependency since 'imply' addresses
the unmet direct dependency, which 'select' could cause.

Signed-off-by: default avatarMasahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: default avatarDirk Gouders <dirk@gouders.net>
parent f1575595

Documentation/kbuild/kconfig-language.txt

+1 −2
Original line number Diff line number Diff line
@@ -545,7 +545,7 @@ make KBUILD_KCONFIG=Documentation/kbuild/Kconfig.recursion-issue-02 allnoconfig 
Practical solutions to kconfig recursive issue

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



Developers who run into the recursive Kconfig issue have three options

Developers who run into the recursive Kconfig issue have two options

at their disposal. We document them below and also provide a list of

historical issues resolved through these different solutions.
@@ -553,7 +553,6 @@ historical issues resolved through these different solutions. 
  b) Match dependency semantics:

	b1) Swap all "select FOO" to "depends on FOO" or,

	b2) Swap all "depends on FOO" to "select FOO"

  c) Consider the use of "imply" instead of "select"



The resolution to a) can be tested with the sample Kconfig file

Documentation/kbuild/Kconfig.recursion-issue-01 through the removal

scripts/kconfig/symbol.c

+7 −2
Original line number Diff line number Diff line
@@ -1098,7 +1098,7 @@ static void sym_check_print_recursive(struct symbol *last_sym) 
				sym->name ? sym->name : "<choice>",

				next_sym->name ? next_sym->name : "<choice>");

		} else {

			fprintf(stderr, "%s:%d:\tsymbol %s is selected by %s\n",

			fprintf(stderr, "%s:%d:\tsymbol %s is selected or implied by %s\n",

				prop->file->name, prop->lineno,

				sym->name ? sym->name : "<choice>",

				next_sym->name ? next_sym->name : "<choice>");
@@ -1161,8 +1161,13 @@ static struct symbol *sym_check_sym_deps(struct symbol *sym) 
	if (sym2)

		goto out;



	sym2 = sym_check_expr_deps(sym->implied.expr);

	if (sym2)

		goto out;



	for (prop = sym->prop; prop; prop = prop->next) {

		if (prop->type == P_CHOICE || prop->type == P_SELECT)

		if (prop->type == P_CHOICE || prop->type == P_SELECT ||

		    prop->type == P_IMPLY)

			continue;

		stack.prop = prop;

		sym2 = sym_check_expr_deps(prop->visible.expr);

scripts/kconfig/tests/err_recursive_dep/Kconfig

+2 −1
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0



# depends on itself



config A
@@ -31,7 +33,6 @@ config D2 
	bool



# depends on and imply

# This is not recursive dependency



config E1

	bool "E1"

scripts/kconfig/tests/err_recursive_dep/expected_stderr

+23 −15
Original line number Diff line number Diff line 
Kconfig:9:error: recursive dependency detected!

Kconfig:9:	symbol B is selected by B

Kconfig:11:error: recursive dependency detected!

Kconfig:11:	symbol B is selected or implied by B

For a resolution refer to Documentation/kbuild/kconfig-language.txt

subsection "Kconfig recursive dependency limitations"



Kconfig:3:error: recursive dependency detected!

Kconfig:3:	symbol A depends on A

Kconfig:5:error: recursive dependency detected!

Kconfig:5:	symbol A depends on A

For a resolution refer to Documentation/kbuild/kconfig-language.txt

subsection "Kconfig recursive dependency limitations"



Kconfig:15:error: recursive dependency detected!

Kconfig:15:	symbol C1 depends on C2

Kconfig:19:	symbol C2 depends on C1

Kconfig:17:error: recursive dependency detected!

Kconfig:17:	symbol C1 depends on C2

Kconfig:21:	symbol C2 depends on C1

For a resolution refer to Documentation/kbuild/kconfig-language.txt

subsection "Kconfig recursive dependency limitations"



Kconfig:30:error: recursive dependency detected!

Kconfig:30:	symbol D2 is selected by D1

Kconfig:25:	symbol D1 depends on D2

Kconfig:32:error: recursive dependency detected!

Kconfig:32:	symbol D2 is selected or implied by D1

Kconfig:27:	symbol D1 depends on D2

For a resolution refer to Documentation/kbuild/kconfig-language.txt

subsection "Kconfig recursive dependency limitations"



Kconfig:59:error: recursive dependency detected!

Kconfig:59:	symbol G depends on G

Kconfig:37:error: recursive dependency detected!

Kconfig:37:	symbol E1 depends on E2

Kconfig:42:	symbol E2 is selected or implied by E1

For a resolution refer to Documentation/kbuild/kconfig-language.txt

subsection "Kconfig recursive dependency limitations"



Kconfig:50:error: recursive dependency detected!

Kconfig:50:	symbol F2 depends on F1

Kconfig:48:	symbol F1 default value contains F2
 
Kconfig:60:error: recursive dependency detected!

Kconfig:60:	symbol G depends on G

For a resolution refer to Documentation/kbuild/kconfig-language.txt

subsection "Kconfig recursive dependency limitations"



Kconfig:51:error: recursive dependency detected!

Kconfig:51:	symbol F2 depends on F1

Kconfig:49:	symbol F1 default value contains F2

For a resolution refer to Documentation/kbuild/kconfig-language.txt

subsection "Kconfig recursive dependency limitations"

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