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From:   Ulf Magnusson <ulfalizer@gmail.com>
Date:   Sun, 1 Apr 2018 04:27:27 +0200
Message-ID: <CAFkk2KTpTXPzNpe6L33_a4YJ=DD0pwz+iEjvm-c1gVeCJGn_6w@mail.gmail.com>
Subject: Re: [PATCH v2 04/21] kconfig: reference environments directly and
 remove 'option env=' syntax
To:     Masahiro Yamada <yamada.masahiro@socionext.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Kees Cook <keescook@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Luis R . Rodriguez" <mcgrof@kernel.org>,
        Nicolas Pitre <nico@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Here's a more in-depth review:

On Tue, Mar 27, 2018 at 7:29 AM, Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> To get an environment value, Kconfig needs to define a symbol using
> "option env=" syntax.  It is tedious to add a config entry for each
> environment given that we need more environments such as 'CC', 'AS',

"Environment variables" would be clearer. I've never seen them called
"environments".

> 'srctree' etc. to evaluate the compiler capability in Kconfig.
>
> Adding '$' to symbols is weird.  Kconfig can reference symbols directly
> like this:
>
>   config FOO
>           string
>           default BAR
>
> So, I want to use the following syntax to get environment 'BAR' from
> the system:
>
>   config FOO
>           string
>           default $BAR
>
> Looking at the code, the symbols prefixed with 'S' are expanded by:
>  - conf_expand_value()
>    This is used to expand 'arch/$ARCH/defconfig' and 'defconfig_list'
>  - expand_string_value()
>    This is used to expand strings in 'source' and 'mainmenu'
>
> All of them are fixed values independent of user configuration.  So,
> this kind of syntax should be moved to simply take the environment.
>
> This change makes the code much cleaner.  The bounce symbols 'SRCARCH',
> 'ARCH', 'SUBARCH', 'KERNELVERSION' are gone.
>
> sym_init() hard-coding 'UNAME_RELEASE' is also gone.  'UNAME_RELEASE'
> should be be given from the environment.
>
> ARCH_DEFCONFIG is a normal symbol, so it should be simply referenced
> by 'default ARCH_DEFCONFIG'.
>
> The environments are expanding in the lexer; when '$' is encountered,

s/environments/environment variables/

> it is expanded, and resulted strings are pushed back to the input
> stream.  This makes the implementation simpler.
>
> For example, the following code works.
>
> [Example code]
>
>   config TOOLCHAIN_LIST
>           string
>           default "My tools: CC=$CC, AS=$AS, CPP=$CPP"
>
> [Result]
>
>   $ make -s alldefconfig && tail -n 1 .config
>   CONFIG_TOOLCHAIN_LIST="My tools: CC=gcc, AS=as, CPP=gcc -E"
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
>
> I tested all 'make *config' for arch architectures.
> I confirmed this commit still produced the same result
> (by my kconfig test tool).
>
>
> Changes in v2:
>   - Move the string expansion to the lexer phase.
>   - Split environment helpers to env.c
>
>  Documentation/kbuild/kconfig-language.txt |  8 ---
>  Kconfig                                   |  4 --
>  Makefile                                  |  3 +-
>  arch/sh/Kconfig                           |  4 +-
>  arch/sparc/Kconfig                        |  4 +-
>  arch/tile/Kconfig                         |  2 +-
>  arch/um/Kconfig.common                    |  4 --
>  arch/x86/Kconfig                          |  4 +-
>  arch/x86/um/Kconfig                       |  4 +-
>  init/Kconfig                              | 10 +---
>  scripts/kconfig/confdata.c                | 31 +---------
>  scripts/kconfig/env.c                     | 95 +++++++++++++++++++++++++++++++
>  scripts/kconfig/kconf_id.c                |  1 -
>  scripts/kconfig/lkc.h                     |  8 +--
>  scripts/kconfig/menu.c                    |  3 -
>  scripts/kconfig/symbol.c                  | 56 ------------------
>  scripts/kconfig/util.c                    | 75 ++++++++----------------
>  scripts/kconfig/zconf.l                   | 20 ++++++-
>  scripts/kconfig/zconf.y                   |  2 +-
>  19 files changed, 158 insertions(+), 180 deletions(-)
>  create mode 100644 scripts/kconfig/env.c
>
> diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
> index f5b9493..0e966e8 100644
> --- a/Documentation/kbuild/kconfig-language.txt
> +++ b/Documentation/kbuild/kconfig-language.txt
> @@ -198,14 +198,6 @@ applicable everywhere (see syntax).
>      enables the third modular state for all config symbols.
>      At most one symbol may have the "modules" option set.
>
> -  - "env"=<value>
> -    This imports the environment variable into Kconfig. It behaves like
> -    a default, except that the value comes from the environment, this
> -    also means that the behaviour when mixing it with normal defaults is
> -    undefined at this point. The symbol is currently not exported back
> -    to the build environment (if this is desired, it can be done via
> -    another symbol).
> -

The new behavior needs to be documented later as well (but iirc you
already mentioned that somewhere else).

>    - "allnoconfig_y"
>      This declares the symbol as one that should have the value y when
>      using "allnoconfig". Used for symbols that hide other symbols.
> diff --git a/Kconfig b/Kconfig
> index 8c4c1cb..e6ece5b 100644
> --- a/Kconfig
> +++ b/Kconfig
> @@ -5,8 +5,4 @@
>  #
>  mainmenu "Linux/$ARCH $KERNELVERSION Kernel Configuration"
>
> -config SRCARCH
> -       string
> -       option env="SRCARCH"
> -
>  source "arch/$SRCARCH/Kconfig"
> diff --git a/Makefile b/Makefile
> index 5c395ed..4ae1486 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -284,7 +284,8 @@ include scripts/Kbuild.include
>  # Read KERNELRELEASE from include/config/kernel.release (if it exists)
>  KERNELRELEASE = $(shell cat include/config/kernel.release 2> /dev/null)
>  KERNELVERSION = $(VERSION)$(if $(PATCHLEVEL),.$(PATCHLEVEL)$(if $(SUBLEVEL),.$(SUBLEVEL)))$(EXTRAVERSION)
> -export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION
> +UNAME_RELEASE := $(shell uname --release)
> +export VERSION PATCHLEVEL SUBLEVEL KERNELRELEASE KERNELVERSION UNAME_RELEASE
>
>  # SUBARCH tells the usermode build what the underlying arch is.  That is set
>  # first, and if a usermode build is happening, the "ARCH=um" on the command
> diff --git a/arch/sh/Kconfig b/arch/sh/Kconfig
> index 97fe293..14f3ef1 100644
> --- a/arch/sh/Kconfig
> +++ b/arch/sh/Kconfig
> @@ -57,7 +57,7 @@ config SUPERH
>           <http://www.linux-sh.org/>.
>
>  config SUPERH32
> -       def_bool ARCH = "sh"
> +       def_bool "$ARCH" = "sh"
>         select HAVE_KPROBES
>         select HAVE_KRETPROBES
>         select HAVE_IOREMAP_PROT if MMU && !X2TLB
> @@ -76,7 +76,7 @@ config SUPERH32
>         select HAVE_CC_STACKPROTECTOR
>
>  config SUPERH64
> -       def_bool ARCH = "sh64"
> +       def_bool "$ARCH" = "sh64"
>         select HAVE_EXIT_THREAD
>         select KALLSYMS
>
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 8767e45..86b852e 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -1,6 +1,6 @@
>  config 64BIT
> -       bool "64-bit kernel" if ARCH = "sparc"
> -       default ARCH = "sparc64"
> +       bool "64-bit kernel" if "$ARCH" = "sparc"
> +       default "$ARCH" = "sparc64"
>         help
>           SPARC is a family of RISC microprocessors designed and marketed by
>           Sun Microsystems, incorporated.  They are very widely found in Sun
> diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
> index ef9d403..acc2182 100644
> --- a/arch/tile/Kconfig
> +++ b/arch/tile/Kconfig
> @@ -119,7 +119,7 @@ config HVC_TILE
>  # Building with ARCH=tilegx (or ARCH=tile) implies using the
>  # 64-bit TILE-Gx toolchain, so force CONFIG_TILEGX on.
>  config TILEGX
> -       def_bool ARCH != "tilepro"
> +       def_bool "$ARCH" != "tilepro"
>         select ARCH_SUPPORTS_ATOMIC_RMW
>         select GENERIC_IRQ_LEGACY_ALLOC_HWIRQ
>         select HAVE_ARCH_JUMP_LABEL
> diff --git a/arch/um/Kconfig.common b/arch/um/Kconfig.common
> index c68add8..07f84c8 100644
> --- a/arch/um/Kconfig.common
> +++ b/arch/um/Kconfig.common
> @@ -54,10 +54,6 @@ config HZ
>         int
>         default 100
>
> -config SUBARCH
> -       string
> -       option env="SUBARCH"
> -
>  config NR_CPUS
>         int
>         range 1 1
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 0fa71a7..986fb0a 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1,8 +1,8 @@
>  # SPDX-License-Identifier: GPL-2.0
>  # Select 32 or 64 bit
>  config 64BIT
> -       bool "64-bit kernel" if ARCH = "x86"
> -       default ARCH != "i386"
> +       bool "64-bit kernel" if "$ARCH" = "x86"
> +       default "$ARCH" != "i386"
>         ---help---
>           Say yes to build a 64-bit kernel - formerly known as x86_64
>           Say no to build a 32-bit kernel - formerly known as i386
> diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig
> index 13ed827..d355413 100644
> --- a/arch/x86/um/Kconfig
> +++ b/arch/x86/um/Kconfig
> @@ -16,8 +16,8 @@ config UML_X86
>         select GENERIC_FIND_FIRST_BIT
>
>  config 64BIT
> -       bool "64-bit kernel" if SUBARCH = "x86"
> -       default SUBARCH != "i386"
> +       bool "64-bit kernel" if $SUBARCH = "x86"
> +       default $SUBARCH != "i386"
>
>  config X86_32
>         def_bool !64BIT
> diff --git a/init/Kconfig b/init/Kconfig
> index df18492..b4814e6 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1,11 +1,3 @@
> -config ARCH
> -       string
> -       option env="ARCH"
> -
> -config KERNELVERSION
> -       string
> -       option env="KERNELVERSION"
> -
>  config DEFCONFIG_LIST
>         string
>         depends on !UML
> @@ -13,7 +5,7 @@ config DEFCONFIG_LIST
>         default "/lib/modules/$UNAME_RELEASE/.config"
>         default "/etc/kernel-config"
>         default "/boot/config-$UNAME_RELEASE"
> -       default "$ARCH_DEFCONFIG"
> +       default ARCH_DEFCONFIG
>         default "arch/$ARCH/defconfig"
>
>  config CONSTRUCTORS
> diff --git a/scripts/kconfig/confdata.c b/scripts/kconfig/confdata.c
> index df26c7b..98c2014 100644
> --- a/scripts/kconfig/confdata.c
> +++ b/scripts/kconfig/confdata.c
> @@ -81,39 +81,13 @@ const char *conf_get_autoconfig_name(void)
>         return name ? name : "include/config/auto.conf";
>  }
>
> -static char *conf_expand_value(const char *in)
> -{
> -       struct symbol *sym;
> -       const char *src;
> -       static char res_value[SYMBOL_MAXLENGTH];
> -       char *dst, name[SYMBOL_MAXLENGTH];
> -
> -       res_value[0] = 0;
> -       dst = name;
> -       while ((src = strchr(in, '$'))) {
> -               strncat(res_value, in, src - in);
> -               src++;
> -               dst = name;
> -               while (isalnum(*src) || *src == '_')
> -                       *dst++ = *src++;
> -               *dst = 0;
> -               sym = sym_lookup(name, 0);
> -               sym_calc_value(sym);
> -               strcat(res_value, sym_get_string_value(sym));
> -               in = src;
> -       }
> -       strcat(res_value, in);
> -
> -       return res_value;
> -}
> -
>  char *conf_get_default_confname(void)
>  {
>         struct stat buf;
>         static char fullname[PATH_MAX+1];
>         char *env, *name;
>
> -       name = conf_expand_value(conf_defname);
> +       name = expand_string_value(conf_defname);
>         env = getenv(SRCTREE);
>         if (env) {
>                 sprintf(fullname, "%s/%s", env, name);
> @@ -274,7 +248,8 @@ int conf_read_simple(const char *name, int def)
>                         if (expr_calc_value(prop->visible.expr) == no ||
>                             prop->expr->type != E_SYMBOL)
>                                 continue;
> -                       name = conf_expand_value(prop->expr->left.sym->name);
> +                       sym_calc_value(prop->expr->left.sym);
> +                       name = sym_get_string_value(prop->expr->left.sym);
>                         in = zconf_fopen(name);
>                         if (in) {
>                                 conf_message(_("using defaults found in %s"),
> diff --git a/scripts/kconfig/env.c b/scripts/kconfig/env.c
> new file mode 100644
> index 0000000..9702f5c
> --- /dev/null
> +++ b/scripts/kconfig/env.c
> @@ -0,0 +1,95 @@
> +// SPDX-License-Identifier: GPL-2.0
> +//
> +// Copyright (C) 2018 Masahiro Yamada <yamada.masahiro@socionext.com>
> +
> +static LIST_HEAD(env_list);
> +
> +struct env {
> +       char *name;
> +       char *value;
> +       struct list_head node;
> +};
> +
> +static struct env *env_list_lookup(const char *name)
> +{
> +       struct env *e;
> +
> +       list_for_each_entry(e, &env_list, node) {
> +               if (!strcmp(name, e->name))
> +                       return e;
> +       }
> +
> +       return NULL;
> +}

This function might be unnecessary -- see below.

> +
> +static void env_list_add(const char *name, const char *value)
> +{
> +       struct env *e;
> +
> +       e = xmalloc(sizeof(*e));
> +       e->name = xstrdup(name);
> +       e->value = xstrdup(value);
> +
> +       list_add_tail(&e->node, &env_list);
> +}
> +
> +static void env_list_del(struct env *e)
> +{
> +       list_del(&e->node);
> +       free(e->name);
> +       free(e->value);
> +       free(e);
> +}
> +
> +/* the returned pointer must be freed when done */
> +static char *env_expand(const char *name)

This function is basically just getenv() with some dependency
housekeeping added. A name like env_get() or env_lookup() would be
clearer I think.

> +{
> +       struct env *e;
> +       const char *value;
> +

> +       e = env_list_lookup(name);
> +       if (e)
> +               return xstrdup(e->value);

Not sure this bit is needed. It is always safe to get the value from
getenv(). See below.

> +
> +       value = getenv(name);
> +       if (!value) {
> +               fprintf(stderr, "environment variable \"%s\" undefined\n", name);
> +               value = "";
> +       }
> +
> +       /*
> +        * we need to remember all referenced environments.

s/environments/environment variables/

> +        * They will be written out to include/config/auto.conf.cmd
> +        */
> +       env_list_add(name, value);

AFAICS, we only need the following functionality:

    1. Record referenced environment variables along with their value

    2. Go through all the recorded environment variables and write
dependency information

For (1), I think it would be better to simply have env_list_add() (or
some other suitable name) add the variable to the list if it isn't
already there (like a kind of set). It is always safe to get the value
of the environment variable from getenv(), and that seems less
confusing.

> +
> +       return xstrdup(value);

The returned string is never modified, and the result from getenv()
never gets stale, so I think the strdup() is unnecessary. The function
could return a const char * to avoid accidental modification.

> +}
> +
> +/* works like env_expand, but 'name' does not need to be null-terminated */
> +char *env_expand_n(const char *name, size_t n)

Could be renamed to something like env_get_n(), and could return a
const char * if the above modification is made.

> +{
> +       char *tmp, *res;
> +
> +       tmp = xmalloc(n + 1);
> +       memcpy(tmp, name, n);
> +       *(tmp + n) = '\0';
> +
> +       res = env_expand(tmp);
> +
> +       free(tmp);
> +
> +       return res;
> +}
> +
> +void env_write_dep(FILE *f, const char *autoconfig_name)
> +{
> +       struct env *env, *tmp;
> +
> +       list_for_each_entry_safe(env, tmp, &env_list, node) {
> +               fprintf(f, "ifneq \"$(%s)\" \"%s\"\n", env->name, env->value);
> +               fprintf(f, "%s: FORCE\n", autoconfig_name);
> +               fprintf(f, "endif\n");
> +               env_list_del(env);
> +       }
> +}
> diff --git a/scripts/kconfig/kconf_id.c b/scripts/kconfig/kconf_id.c
> index 3ea9c5f..b3e0ea0 100644
> --- a/scripts/kconfig/kconf_id.c
> +++ b/scripts/kconfig/kconf_id.c
> @@ -32,7 +32,6 @@ static struct kconf_id kconf_id_array[] = {
>         { "on",                 T_ON,                   TF_PARAM },
>         { "modules",            T_OPT_MODULES,          TF_OPTION },
>         { "defconfig_list",     T_OPT_DEFCONFIG_LIST,   TF_OPTION },
> -       { "env",                T_OPT_ENV,              TF_OPTION },
>         { "allnoconfig_y",      T_OPT_ALLNOCONFIG_Y,    TF_OPTION },
>  };
>
> diff --git a/scripts/kconfig/lkc.h b/scripts/kconfig/lkc.h
> index c8d9e55..03d007f 100644
> --- a/scripts/kconfig/lkc.h
> +++ b/scripts/kconfig/lkc.h
> @@ -58,7 +58,6 @@ enum conf_def_mode {
>
>  #define T_OPT_MODULES          1
>  #define T_OPT_DEFCONFIG_LIST   2
> -#define T_OPT_ENV              3
>  #define T_OPT_ALLNOCONFIG_Y    4

Renumber to 3? Looks like a bitmask to me otherwise.

>
>  struct kconf_id {
> @@ -95,6 +94,10 @@ static inline void xfwrite(const void *str, size_t len, size_t count, FILE *out)
>                 fprintf(stderr, "Error in writing or end of file.\n");
>  }
>
> +/* env.c */
> +char *env_expand_n(const char *name, size_t n);
> +void env_write_dep(FILE *f, const char *auto_conf_name);
> +
>  /* menu.c */
>  void _menu_init(void);
>  void menu_warn(struct menu *menu, const char *fmt, ...);
> @@ -135,9 +138,6 @@ void str_printf(struct gstr *gs, const char *fmt, ...);
>  const char *str_get(struct gstr *gs);
>
>  /* symbol.c */
> -extern struct expr *sym_env_list;
> -
> -void sym_init(void);
>  void sym_clear_all_valid(void);
>  struct symbol *sym_choice_default(struct symbol *sym);
>  const char *sym_get_string_default(struct symbol *sym);
> diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
> index 5c5c137..8148305 100644
> --- a/scripts/kconfig/menu.c
> +++ b/scripts/kconfig/menu.c
> @@ -214,9 +214,6 @@ void menu_add_option(int token, char *arg)
>                         zconf_error("trying to redefine defconfig symbol");
>                 sym_defconfig_list->flags |= SYMBOL_AUTO;
>                 break;
> -       case T_OPT_ENV:
> -               prop_add_env(arg);
> -               break;
>         case T_OPT_ALLNOCONFIG_Y:
>                 current_entry->sym->flags |= SYMBOL_ALLNOCONFIG_Y;
>                 break;
> diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
> index 03143b2..7c9a88e 100644
> --- a/scripts/kconfig/symbol.c
> +++ b/scripts/kconfig/symbol.c
> @@ -33,33 +33,6 @@ struct symbol *sym_defconfig_list;
>  struct symbol *modules_sym;
>  tristate modules_val;
>
> -struct expr *sym_env_list;
> -
> -static void sym_add_default(struct symbol *sym, const char *def)
> -{
> -       struct property *prop = prop_alloc(P_DEFAULT, sym);
> -
> -       prop->expr = expr_alloc_symbol(sym_lookup(def, SYMBOL_CONST));
> -}
> -
> -void sym_init(void)
> -{
> -       struct symbol *sym;
> -       struct utsname uts;
> -       static bool inited = false;
> -
> -       if (inited)
> -               return;
> -       inited = true;
> -
> -       uname(&uts);
> -
> -       sym = sym_lookup("UNAME_RELEASE", 0);
> -       sym->type = S_STRING;
> -       sym->flags |= SYMBOL_AUTO;
> -       sym_add_default(sym, uts.release);
> -}
> -
>  enum symbol_type sym_get_type(struct symbol *sym)
>  {
>         enum symbol_type type = sym->type;
> @@ -1348,32 +1321,3 @@ const char *prop_get_type_name(enum prop_type type)
>         }
>         return "unknown";
>  }
> -
> -static void prop_add_env(const char *env)
> -{
> -       struct symbol *sym, *sym2;
> -       struct property *prop;
> -       char *p;
> -
> -       sym = current_entry->sym;
> -       sym->flags |= SYMBOL_AUTO;
> -       for_all_properties(sym, prop, P_ENV) {
> -               sym2 = prop_get_symbol(prop);
> -               if (strcmp(sym2->name, env))
> -                       menu_warn(current_entry, "redefining environment symbol from %s",
> -                                 sym2->name);
> -               return;
> -       }
> -
> -       prop = prop_alloc(P_ENV, sym);
> -       prop->expr = expr_alloc_symbol(sym_lookup(env, SYMBOL_CONST));
> -
> -       sym_env_list = expr_alloc_one(E_LIST, sym_env_list);
> -       sym_env_list->right.sym = sym;
> -
> -       p = getenv(env);
> -       if (p)
> -               sym_add_default(sym, p);
> -       else
> -               menu_warn(current_entry, "environment variable %s undefined", env);
> -}
> diff --git a/scripts/kconfig/util.c b/scripts/kconfig/util.c
> index 22201a4..136e497 100644
> --- a/scripts/kconfig/util.c
> +++ b/scripts/kconfig/util.c
> @@ -8,16 +8,18 @@
>  #include <stdarg.h>
>  #include <stdlib.h>
>  #include <string.h>
> +
> +#include "list.h"
>  #include "lkc.h"
>
>  /*
> - * Expand symbol's names embedded in the string given in argument. Symbols'
> - * name to be expanded shall be prefixed by a '$'. Unknown symbol expands to
> + * Expand environments embedded in the string given in argument. Environments

s/environments/environment variables/

> + * to be expanded shall be prefixed by a '$'. Unknown environment expands to
>   * the empty string.
>   */
>  char *expand_string_value(const char *in)
>  {
> -       const char *src;
> +       const char *p, *q;
>         char *res;
>         size_t reslen;
>
> @@ -25,39 +27,28 @@ char *expand_string_value(const char *in)
>          * Note: 'in' might come from a token that's about to be
>          * freed, so make sure to always allocate a new string
>          */
> -       reslen = strlen(in) + 1;
> -       res = xmalloc(reslen);
> -       res[0] = '\0';
> -
> -       while ((src = strchr(in, '$'))) {
> -               char *p, name[SYMBOL_MAXLENGTH];
> -               const char *symval = "";
> -               struct symbol *sym;
> -               size_t newlen;
> -
> -               strncat(res, in, src - in);
> -               src++;
> -
> -               p = name;
> -               while (isalnum(*src) || *src == '_')
> -                       *p++ = *src++;
> -               *p = '\0';
> -
> -               sym = sym_find(name);
> -               if (sym != NULL) {
> -                       sym_calc_value(sym);
> -                       symval = sym_get_string_value(sym);
> -               }
> +       res = xmalloc(1);
> +       *res = '\0';
>
> -               newlen = strlen(res) + strlen(symval) + strlen(src) + 1;
> -               if (newlen > reslen) {
> -                       reslen = newlen;
> -                       res = xrealloc(res, reslen);
> -               }
> +       while ((p = strchr(in, '$'))) {
> +               char *new;
> +
> +               q = p + 1;
> +               while (isalnum(*q) || *q == '_')
> +                       q++;
>
> -               strcat(res, symval);
> -               in = src;
> +               new = env_expand_n(p + 1, q - p - 1);

'value' might be a clearer name than 'new'.

> +
> +               reslen = strlen(res) + (p - in) + strlen(new) + 1;
> +               res = xrealloc(res, reslen);
> +               strncat(res, in, p - in);
> +               strcat(res, new);
> +               free(new);

Not needed it env_expand_n() (env_get_n()) is modified to return the
value from getenv() directly. 'new' is never modified either.

> +               in = q;
>         }
> +
> +       reslen = strlen(res) + strlen(in) + 1;
> +       res = xrealloc(res, reslen);
>         strcat(res, in);
>
>         return res;
> @@ -87,8 +78,6 @@ struct file *file_lookup(const char *name)
>  /* write a dependency file as used by kbuild to track dependencies */
>  int file_write_dep(const char *name)
>  {
> -       struct symbol *sym, *env_sym;
> -       struct expr *e;
>         struct file *file;
>         FILE *out;
>
> @@ -107,21 +96,7 @@ int file_write_dep(const char *name)
>         fprintf(out, "\n%s: \\\n"
>                      "\t$(deps_config)\n\n", conf_get_autoconfig_name());
>
> -       expr_list_for_each_sym(sym_env_list, e, sym) {
> -               struct property *prop;
> -               const char *value;
> -
> -               prop = sym_get_env_prop(sym);
> -               env_sym = prop_get_symbol(prop);
> -               if (!env_sym)
> -                       continue;
> -               value = getenv(env_sym->name);
> -               if (!value)
> -                       value = "";
> -               fprintf(out, "ifneq \"$(%s)\" \"%s\"\n", env_sym->name, value);
> -               fprintf(out, "%s: FORCE\n", conf_get_autoconfig_name());
> -               fprintf(out, "endif\n");
> -       }
> +       env_write_dep(out, conf_get_autoconfig_name());
>
>         fprintf(out, "\n$(deps_config): ;\n");
>         fclose(out);
> diff --git a/scripts/kconfig/zconf.l b/scripts/kconfig/zconf.l
> index 045093d..551ca47 100644
> --- a/scripts/kconfig/zconf.l
> +++ b/scripts/kconfig/zconf.l
> @@ -35,6 +35,7 @@ struct buffer *current_buf;
>
>  static int last_ts, first_ts;
>
> +static void expand_string(const char *in);
>  static void zconf_endhelp(void);
>  static void zconf_endfile(void);
>
> @@ -120,6 +121,7 @@ n   [A-Za-z0-9_-]
>  }
>
>  <PARAM>{
> +       "$".*   expand_string(yytext);
>         "&&"    return T_AND;
>         "||"    return T_OR;
>         "("     return T_OPEN_PAREN;
> @@ -157,12 +159,13 @@ n [A-Za-z0-9_-]
>  }
>
>  <STRING>{
> -       [^'"\\\n]+/\n   {
> +       "$".*   expand_string(yytext);
> +       [^$'"\\\n]+/\n  {
>                 append_string(yytext, yyleng);
>                 yylval.string = text;
>                 return T_WORD_QUOTE;
>         }
> -       [^'"\\\n]+      {
> +       [^$'"\\\n]+     {
>                 append_string(yytext, yyleng);
>         }
>         \\.?/\n {
> @@ -249,6 +252,19 @@ n  [A-Za-z0-9_-]
>  }
>
>  %%
> +static void expand_string(const char *in)
> +{
> +       char *p, *q;
> +
> +       p = expand_string_value(in);
> +
> +       q = p + strlen(p);
> +       while (q > p)
> +               unput(*--q);
> +
> +       free(p);
> +}

(In case any other reviewers jump in -- see earlier messages in this
thread for some gotchas related to this.)

> +
>  void zconf_starthelp(void)
>  {
>         new_string();
> diff --git a/scripts/kconfig/zconf.y b/scripts/kconfig/zconf.y
> index 262c464..4ff4ac9 100644
> --- a/scripts/kconfig/zconf.y
> +++ b/scripts/kconfig/zconf.y
> @@ -534,7 +534,6 @@ void conf_parse(const char *name)
>
>         zconf_initscan(name);
>
> -       sym_init();
>         _menu_init();
>
>         if (getenv("ZCONF_DEBUG"))
> @@ -775,6 +774,7 @@ void zconfdump(FILE *out)
>  }
>
>  #include "zconf.lex.c"
> +#include "env.c"
>  #include "util.c"
>  #include "confdata.c"
>  #include "expr.c"
> --
> 2.7.4
>

Cheers,
Ulf