Commit 8bfd6f09 authored Jul 08, 2024 by Masahiro Yamada

kconfig: call expr_eliminate_yn() at least once in expr_eliminate_dups()



Kconfig simplifies expressions, but redundant '&&' and '||' operators
involving constant symbols 'y' and 'n' are sometimes trimmed and
sometimes not.

[Test Code]

    config DEP
            def_bool y

    config A
            bool "A"
            depends on DEP && y

    config B
            bool "B"
            depends on DEP && y && y

[Result]

    $ make helpnewconfig
      [ snip ]
    -----

    There is no help available for this option.
    Symbol: A [=n]
    Type  : bool
    Defined at Kconfig:4
      Prompt: A
      Depends on: DEP [=y] && y [=y]
      Location:
        -> A (A [=n])

    -----
    -----

    There is no help available for this option.
    Symbol: B [=n]
    Type  : bool
    Defined at Kconfig:8
      Prompt: B
      Depends on: DEP [=y]
      Location:
        -> B (B [=n])

    -----

The dependency for A, 'DEP && y', remains as-is, while that for B,
'DEP && y && y', has been reduced to 'DEP'.

Currently, expr_eliminate_dups() calls expr_eliminate_yn() only when
trans_count != 0, in other words, only when expr_eliminate_dups1() has
trimmed at least one leaf. It fails to trim a single '&& y', etc.

To fix this inconsistent behavior, expr_eliminate_yn() should be called
at least once even if no leaf has been trimmed.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

parent d67015ee

scripts/kconfig/expr.c

+2 −5

Original line number	Diff line number	Diff line
		@@ -637,7 +637,7 @@ struct expr expr_eliminate_dups(struct expr e)
		return e;

		oldcount = trans_count;
		while (1) {
		do {
		trans_count = 0;
		switch (e->type) {
		case E_OR: case E_AND:
		@@ -645,11 +645,8 @@ struct expr expr_eliminate_dups(struct expr e)
		default:
		;
		}
		if (!trans_count)
		/* No simplifications done in this pass. We're done */
		break;
		e = expr_eliminate_yn(e);
		}
		} while (trans_count); /* repeat until we get no more simplifications */
		trans_count = oldcount;
		return e;
		}