This has not been used since commit e911503085ae ("Kconfig: Remove
bad inference rules expr_eliminate_dups2()").

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

This flag is set to symbols that are not intended to be written
to the .config file.

Since commit b75b0a819af9 ("kconfig: change defconfig_list option to
environment variable"), SYMBOL_NO_WRITE is only set to choices.

Therefore, (sym->flags & SYMBOL_NO_WRITE) is equivalent to
sym_is_choice(sym). This flag is no longer necessary.

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

The 'choice' statement is primarily used to exclusively select one
option, but the 'optional' property allows all entries to be disabled.

In the following example, both A and B can be disabled simultaneously:

    choice
            prompt "choose A, B, or nothing"
            optional

    config A
            bool "A"

    config B
            bool "B"

    endchoice

You can achieve the equivalent outcome by other means.

A common solution is to add another option to guard the choice block.
In the following example, you can set ENABLE_A_B_CHOICE=n to disable
the entire choice block:

    choice
            prompt "choose A or B"
            depends on ENABLE_A_B_CHOICE

    config A
            bool "A"

    config B
            bool "B"

    endchoice

Another approach is to insert one more entry:

    choice
            prompt "choose A, B, or disable both"

    config A
            bool "A"

    config B
            bool "B"

    config DISABLE_A_AND_B
            bool "choose this to disable both A and B"

    endchoice

Some real examples are DEBUG_INFO_NONE, INITRAMFS_COMPRESSION_NONE,
LTO_NONE, etc.

The 'optional' property is even more unnecessary for a tristate choice.

Without the 'optional' property, you can disable A and B; you can set
'm' in the choice prompt, and disable A and B individually:

    choice
            prompt "choose one built-in or make them modular"

    config A
            tristate "A"

    config B
            tristate "B"

    endchoice

In conclusion, the 'optional' property was unneeded.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

All symbols except choices have a name.

Previously, choices were allowed to have a name, but commit c83f020973bc
("kconfig: remove named choice support") eliminated that possibility.

Now, it is easy to distinguish choices from normal symbols; if the name
is NULL, it is a choice.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>

Currently, there is no direct link from (struct symbol) to (struct menu).

It is still possible to access associated menus through the P_SYMBOL
property, because property::menu is the relevant menu entry, but it
results in complex code, as seen in get_symbol_str().

Use a linked list for simpler traversal of relevant menus.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

Use helper macros in hashtable.h for generic hashtable implementation.

We can git rid of the hash head index of for_all_symbols().

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

The struct list_head is often embedded in other structures, while other
code is used in C functions.

By separating struct list_head into its own header, other headers are no
longer required to include the entire list.h.

This is similar to the kernel space, where struct list_head is defined
in <linux/types.h> instead of <linux/list.h>.

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

Currently, file_lookup() returns a pointer to (struct file), but the
callers use only file->name.

Make it return the ->name member directly.

This adjustment encapsulates struct file and file_list as internal
implementation.

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

Call malloc() just once to allocate needed memory.

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

struct file has two link nodes, 'next' and 'parent'.

The former is used to link files in the 'file_list' linked list,
which manages the list of Kconfig files seen so far.

The latter is used to link files in the 'current_file' linked list,
which manages the inclusion ("source") tree.

The latter should be tracked together with the lexer state.

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