Kconfig updates for v4.16

A pretty big batch of Kconfig updates. I have to mention the lexer
 and parser of Kconfig are now built from real .l and .y sources.
 So, flex and bison are the requirement for building the kernel.
 Both of them (unlike gperf) have been stable for a long time. This
 change has been tested several weeks in linux-next, and I did not
 receive any problem report about this.
 
 Summary:
 
 - Add checks for mistakes, like the choice default is not in
   choice, help is doubled
 
 - Document data structure and complex code
 
 - Fix various memory leaks
 
 - Change Makefile to build lexer and parser instead of using
   pre-generated C files
 
 - Drop 'boolean' keyword, which is equivalent to 'bool'
 
 - Use default 'yy' prefix and remove unneeded Make variables
 
 - Fix gettext() check for xconfig
 
 - Announce that oldnoconfig will be finally removed
 
 - Make 'Selected by:' and 'Implied by' readable in help and
   search result
 
 - Hide silentoldconfig from 'make help' to stop confusing people
 
 - Fix misc things and cleanups
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Merge tag 'kconfig-v4.16' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kconfig updates from Masahiro Yamada:
 "A pretty big batch of Kconfig updates.

  I have to mention the lexer and parser of Kconfig are now built from
  real .l and .y sources. So, flex and bison are the requirement for
  building the kernel. Both of them (unlike gperf) have been stable for
  a long time. This change has been tested several weeks in linux-next,
  and I did not receive any problem report about this.

  Summary:

   - add checks for mistakes, like the choice default is not in choice,
     help is doubled

   - document data structure and complex code

   - fix various memory leaks

   - change Makefile to build lexer and parser instead of using
     pre-generated C files

   - drop 'boolean' keyword, which is equivalent to 'bool'

   - use default 'yy' prefix and remove unneeded Make variables

   - fix gettext() check for xconfig

   - announce that oldnoconfig will be finally removed

   - make 'Selected by:' and 'Implied by' readable in help and search
     result

   - hide silentoldconfig from 'make help' to stop confusing people

   - fix misc things and cleanups"

* tag 'kconfig-v4.16' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (37 commits)
  kconfig: Remove silentoldconfig from help and docs; fix kconfig/conf's help
  kconfig: make "Selected by:" and "Implied by:" readable
  kconfig: announce removal of oldnoconfig if used
  kconfig: fix make xconfig when gettext is missing
  kconfig: Clarify menu and 'if' dependency propagation
  kconfig: Document 'if' flattening logic
  kconfig: Clarify choice dependency propagation
  kconfig: Document SYMBOL_OPTIONAL logic
  kbuild: remove unnecessary LEX_PREFIX and YACC_PREFIX
  kconfig: use default 'yy' prefix for lexer and parser
  kconfig: make conf_unsaved a local variable of conf_read()
  kconfig: make xfgets() really static
  kconfig: make input_mode static
  kconfig: Warn if there is more than one help text
  kconfig: drop 'boolean' keyword
  kconfig: use bool instead of boolean for type definition attributes, again
  kconfig: Remove menu_end_entry()
  kconfig: Document important expression functions
  kconfig: Document automatic submenu creation code
  kconfig: Fix choice symbol expression leak
  ...

Documentation/admin-guide/README.rst

@@ -170,11 +170,6 @@ Configuring the kernel
                         your existing ./.config file and asking about
                         new config symbols.
 
-     "make silentoldconfig"
-                        Like above, but avoids cluttering the screen
-                        with questions already answered.
-                        Additionally updates the dependencies.
-
      "make olddefconfig"
                         Like above, but sets new symbols to their default
                         values without prompting.

Documentation/process/changes.rst

@@ -32,6 +32,8 @@ you probably needn't concern yourself with isdn4k-utils.
 GNU C                  3.2              gcc --version
 GNU make               3.81             make --version
 binutils               2.20             ld -v
+flex                   2.5.35           flex --version
+bison                  2.0              bison --version
 util-linux             2.10o            fdformat --version
 module-init-tools      0.9.10           depmod -V
 e2fsprogs              1.41.4           e2fsck -V
@@ -79,6 +81,19 @@ The build system has, as of 4.13, switched to using thin archives (`ar T`)
 rather than incremental linking (`ld -r`) for built-in.o intermediate steps.
 This requires binutils 2.20 or newer.
 
+Flex
+----
+
+Since Linux 4.16, the build system generates lexical analyzers
+during build.  This requires flex 2.5.35 or later.
+
+
+Bison
+-----
+
+Since Linux 4.16, the build system generates parsers
+during build.  This requires bison 2.0 or later.
+
 Perl
 ----
 
@@ -333,6 +348,16 @@ Binutils
 
 - <https://www.kernel.org/pub/linux/devel/binutils/>
 
+Flex
+----
+
+- <https://github.com/westes/flex/releases>
+
+Bison
+-----
+
+- <ftp://ftp.gnu.org/gnu/bison/>
+
 OpenSSL
 -------
 

Makefile

@@ -377,6 +377,8 @@ NM		= $(CROSS_COMPILE)nm
 STRIP		= $(CROSS_COMPILE)strip
 OBJCOPY		= $(CROSS_COMPILE)objcopy
 OBJDUMP		= $(CROSS_COMPILE)objdump
+LEX		= flex
+YACC		= bison
 AWK		= awk
 GENKSYMS	= scripts/genksyms/genksyms
 INSTALLKERNEL  := installkernel
@@ -428,7 +430,7 @@ GCC_PLUGINS_CFLAGS :=
 
 export ARCH SRCARCH CONFIG_SHELL HOSTCC HOSTCFLAGS CROSS_COMPILE AS LD CC
 export CPP AR NM STRIP OBJCOPY OBJDUMP HOSTLDFLAGS HOST_LOADLIBES
-export MAKE AWK GENKSYMS INSTALLKERNEL PERL PYTHON UTS_MACHINE
+export MAKE LEX YACC AWK GENKSYMS INSTALLKERNEL PERL PYTHON UTS_MACHINE
 export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS

drivers/firmware/efi/Kconfig

@@ -113,7 +113,7 @@ config EFI_CAPSULE_LOADER
 	  Most users should say N.
 
 config EFI_CAPSULE_QUIRK_QUARK_CSH
-	boolean "Add support for Quark capsules with non-standard headers"
+	bool "Add support for Quark capsules with non-standard headers"
 	depends on X86 && !64BIT
 	select EFI_CAPSULE_LOADER
 	default y

drivers/staging/rtlwifi/Kconfig

@@ -7,6 +7,6 @@ config R8822BE
 	wireless network adapters.
 
 config RTLWIFI_DEBUG_ST
-	boolean
+	bool
 	depends on R8822BE
 	default y

scripts/Makefile.lib

@@ -186,39 +186,49 @@ $(foreach m, $(notdir $1), \
 	$(addprefix $(obj)/, $(foreach s, $3, $($(m:%$(strip $2)=%$(s)))))))
 endef
 
-ifdef REGENERATE_PARSERS
-
 # LEX
 # ---------------------------------------------------------------------------
-LEX_PREFIX = $(if $(LEX_PREFIX_${baseprereq}),$(LEX_PREFIX_${baseprereq}),yy)
-
 quiet_cmd_flex = LEX     $@
-      cmd_flex = flex -o$@ -L -P $(LEX_PREFIX) $<
+      cmd_flex = $(LEX) -o$@ -L $<
 
+ifdef REGENERATE_PARSERS
 .PRECIOUS: $(src)/%.lex.c_shipped
 $(src)/%.lex.c_shipped: $(src)/%.l
 	$(call cmd,flex)
+endif
+
+.PRECIOUS: $(obj)/%.lex.c
+$(filter %.lex.c,$(targets)): $(obj)/%.lex.c: $(src)/%.l FORCE
+	$(call if_changed,flex)
 
 # YACC
 # ---------------------------------------------------------------------------
-YACC_PREFIX = $(if $(YACC_PREFIX_${baseprereq}),$(YACC_PREFIX_${baseprereq}),yy)
-
 quiet_cmd_bison = YACC    $@
-      cmd_bison = bison -o$@ -t -l -p $(YACC_PREFIX) $<
+      cmd_bison = $(YACC) -o$@ -t -l $<
 
+ifdef REGENERATE_PARSERS
 .PRECIOUS: $(src)/%.tab.c_shipped
 $(src)/%.tab.c_shipped: $(src)/%.y
 	$(call cmd,bison)
+endif
+
+.PRECIOUS: $(obj)/%.tab.c
+$(filter %.tab.c,$(targets)): $(obj)/%.tab.c: $(src)/%.y FORCE
+	$(call if_changed,bison)
 
 quiet_cmd_bison_h = YACC    $@
       cmd_bison_h = bison -o/dev/null --defines=$@ -t -l -p $(YACC_PREFIX) $<
 
+ifdef REGENERATE_PARSERS
 .PRECIOUS: $(src)/%.tab.h_shipped
 $(src)/%.tab.h_shipped: $(src)/%.y
 	$(call cmd,bison_h)
-
 endif
 
+.PRECIOUS: $(obj)/%.tab.h
+$(filter %.tab.h,$(targets)): $(obj)/%.tab.h: $(src)/%.y FORCE
+	$(call if_changed,bison_h)
+
 # Shipped files
 # ===========================================================================
 

scripts/kconfig/Makefile

@@ -34,6 +34,8 @@ config: $(obj)/conf
 nconfig: $(obj)/nconf
 	$< $(silent) $(Kconfig)
 
+# This has become an internal implementation detail and is now deprecated
+# for external use.
 silentoldconfig: $(obj)/conf
 	$(Q)mkdir -p include/config include/generated
 	$(Q)test -e include/generated/autoksyms.h || \
@@ -92,6 +94,8 @@ PHONY += oldnoconfig savedefconfig defconfig
 # on its behavior (sets new symbols to their default value but not 'n') with the
 # counter-intuitive name.
 oldnoconfig: olddefconfig
+	@echo "  WARNING: \"oldnoconfig\" target will be removed after Linux 4.19"
+	@echo "            Please use \"olddefconfig\" instead, which is an alias."
 
 savedefconfig: $(obj)/conf
 	$< $(silent) --$@=defconfig $(Kconfig)
@@ -142,7 +146,6 @@ help:
 	@echo  '  oldconfig	  - Update current config utilising a provided .config as base'
 	@echo  '  localmodconfig  - Update current config disabling modules not loaded'
 	@echo  '  localyesconfig  - Update current config converting local mods to core'
-	@echo  '  silentoldconfig - Same as oldconfig, but quietly, additionally update deps'
 	@echo  '  defconfig	  - New config with default from ARCH supplied defconfig'
 	@echo  '  savedefconfig   - Save current config as ./defconfig (minimal config)'
 	@echo  '  allnoconfig	  - New config where all options are answered with no'
@@ -151,8 +154,8 @@ help:
 	@echo  '  alldefconfig    - New config with all symbols set to default'
 	@echo  '  randconfig	  - New config with random answer to all options'
 	@echo  '  listnewconfig   - List new options'
-	@echo  '  olddefconfig	  - Same as silentoldconfig but sets new symbols to their'
+	@echo  '  olddefconfig	  - Same as oldconfig but sets new symbols to their'
-	@echo  '                    default value'
+	@echo  '                    default value without prompting'
 	@echo  '  kvmconfig	  - Enable additional options for kvm guest kernel support'
 	@echo  '  xenconfig       - Enable additional options for xen dom0 and guest kernel support'
 	@echo  '  tinyconfig	  - Configure the tiniest possible kernel'
@@ -191,6 +194,7 @@ gconf-objs	:= gconf.o zconf.tab.o
 
 hostprogs-y := conf nconf mconf kxgettext qconf gconf
 
+targets		+= zconf.tab.c zconf.lex.c
 clean-files	:= qconf.moc .tmp_qtcheck .tmp_gtkcheck
 clean-files	+= zconf.tab.c zconf.lex.c gconf.glade.h
 clean-files     += config.pot linux.pot
@@ -205,14 +209,12 @@ always := dochecklxdialog
 
 # Add environment specific flags
 HOST_EXTRACFLAGS += $(shell $(CONFIG_SHELL) $(srctree)/$(src)/check.sh $(HOSTCC) $(HOSTCFLAGS))
+HOST_EXTRACXXFLAGS += $(shell $(CONFIG_SHELL) $(srctree)/$(src)/check.sh $(HOSTCXX) $(HOSTCXXFLAGS))
 
 # generated files seem to need this to find local include files
 HOSTCFLAGS_zconf.lex.o	:= -I$(src)
 HOSTCFLAGS_zconf.tab.o	:= -I$(src)
 
-LEX_PREFIX_zconf	:= zconf
-YACC_PREFIX_zconf	:= zconf
-
 HOSTLOADLIBES_qconf	= $(KC_QT_LIBS)
 HOSTCXXFLAGS_qconf.o	= $(KC_QT_CFLAGS)
 

scripts/kconfig/conf.c

@@ -20,7 +20,6 @@
 
 static void conf(struct menu *menu);
 static void check_conf(struct menu *menu);
-static void xfgets(char *str, int size, FILE *in);
 
 enum input_mode {
 	oldaskconfig,
@@ -35,7 +34,8 @@ enum input_mode {
 	savedefconfig,
 	listnewconfig,
 	olddefconfig,
-} input_mode = oldaskconfig;
+};
+static enum input_mode input_mode = oldaskconfig;
 
 static int indent = 1;
 static int tty_stdio;
@@ -82,6 +82,13 @@ static void check_stdin(void)
 	}
 }
 
+/* Helper function to facilitate fgets() by Jean Sacren. */
+static void xfgets(char *str, int size, FILE *in)
+{
+	if (!fgets(str, size, in))
+		fprintf(stderr, "\nError in reading or end of file.\n");
+}
+
 static int conf_askvalue(struct symbol *sym, const char *def)
 {
 	enum symbol_type type = sym_get_type(sym);
@@ -477,8 +484,9 @@ static void conf_usage(const char *progname)
 	printf("  --listnewconfig         List new options\n");
 	printf("  --oldaskconfig          Start a new configuration using a line-oriented program\n");
 	printf("  --oldconfig             Update a configuration using a provided .config as base\n");
-	printf("  --silentoldconfig       Same as oldconfig, but quietly, additionally update deps\n");
+	printf("  --silentoldconfig       Similar to oldconfig but generates configuration in\n"
-	printf("  --olddefconfig          Same as silentoldconfig but sets new symbols to their default value\n");
+	       "                          include/{generated/,config/} (oldconfig used to be more verbose)\n");
+	printf("  --olddefconfig          Same as oldconfig but sets new symbols to their default value\n");
 	printf("  --oldnoconfig           An alias of olddefconfig\n");
 	printf("  --defconfig <file>      New config with default defined in <file>\n");
 	printf("  --savedefconfig <file>  Save the minimal current configuration to <file>\n");
@@ -712,12 +720,3 @@ int main(int ac, char **av)
 	}
 	return 0;
 }
-
-/*
- * Helper function to facilitate fgets() by Jean Sacren.
- */
-void xfgets(char *str, int size, FILE *in)
-{
-	if (fgets(str, size, in) == NULL)
-		fprintf(stderr, "\nError in reading or end of file.\n");
-}

scripts/kconfig/confdata.c

@@ -28,7 +28,7 @@ static void conf_message(const char *fmt, ...)
 	__attribute__ ((format (printf, 1, 2)));
 
 static const char *conf_filename;
-static int conf_lineno, conf_warnings, conf_unsaved;
+static int conf_lineno, conf_warnings;
 
 const char conf_defname[] = "arch/$ARCH/defconfig";
 
@@ -290,7 +290,6 @@ load:
 	conf_filename = name;
 	conf_lineno = 0;
 	conf_warnings = 0;
-	conf_unsaved = 0;
 
 	def_flags = SYMBOL_DEF << def;
 	for_all_symbols(i, sym) {
@@ -409,6 +408,7 @@ setsym:
 int conf_read(const char *name)
 {
 	struct symbol *sym;
+	int conf_unsaved = 0;
 	int i;
 
 	sym_set_change_count(0);
@@ -1123,7 +1123,7 @@ void set_all_choice_values(struct symbol *csym)
 bool conf_set_all_new_symbols(enum conf_def_mode mode)
 {
 	struct symbol *sym, *csym;
-	int i, cnt, pby, pty, ptm;	/* pby: probability of boolean  = y
+	int i, cnt, pby, pty, ptm;	/* pby: probability of bool     = y
 					 * pty: probability of tristate = y
 					 * ptm: probability of tristate = m
 					 */

scripts/kconfig/expr.c

@@ -113,7 +113,7 @@ void expr_free(struct expr *e)
 		break;
 	case E_NOT:
 		expr_free(e->left.expr);
-		return;
+		break;
 	case E_EQUAL:
 	case E_GEQ:
 	case E_GTH:
@@ -138,8 +138,18 @@ static int trans_count;
 #define e1 (*ep1)
 #define e2 (*ep2)
 
+/*
+ * expr_eliminate_eq() helper.
+ *
+ * Walks the two expression trees given in 'ep1' and 'ep2'. Any node that does
+ * not have type 'type' (E_OR/E_AND) is considered a leaf, and is compared
+ * against all other leaves. Two equal leaves are both replaced with either 'y'
+ * or 'n' as appropriate for 'type', to be eliminated later.
+ */
 static void __expr_eliminate_eq(enum expr_type type, struct expr **ep1, struct expr **ep2)
 {
+	/* Recurse down to leaves */
+
 	if (e1->type == type) {
 		__expr_eliminate_eq(type, &e1->left.expr, &e2);
 		__expr_eliminate_eq(type, &e1->right.expr, &e2);
@@ -150,12 +160,18 @@ static void __expr_eliminate_eq(enum expr_type type, struct expr **ep1, struct e
 		__expr_eliminate_eq(type, &e1, &e2->right.expr);
 		return;
 	}
+
+	/* e1 and e2 are leaves. Compare them. */
+
 	if (e1->type == E_SYMBOL && e2->type == E_SYMBOL &&
 	    e1->left.sym == e2->left.sym &&
 	    (e1->left.sym == &symbol_yes || e1->left.sym == &symbol_no))
 		return;
 	if (!expr_eq(e1, e2))
 		return;
+
+	/* e1 and e2 are equal leaves. Prepare them for elimination. */
+
 	trans_count++;
 	expr_free(e1); expr_free(e2);
 	switch (type) {
@@ -172,6 +188,35 @@ static void __expr_eliminate_eq(enum expr_type type, struct expr **ep1, struct e
 	}
 }
 
+/*
+ * Rewrites the expressions 'ep1' and 'ep2' to remove operands common to both.
+ * Example reductions:
+ *
+ *	ep1: A && B           ->  ep1: y
+ *	ep2: A && B && C      ->  ep2: C
+ *
+ *	ep1: A || B           ->  ep1: n
+ *	ep2: A || B || C      ->  ep2: C
+ *
+ *	ep1: A && (B && FOO)  ->  ep1: FOO
+ *	ep2: (BAR && B) && A  ->  ep2: BAR
+ *
+ *	ep1: A && (B || C)    ->  ep1: y
+ *	ep2: (C || B) && A    ->  ep2: y
+ *
+ * Comparisons are done between all operands at the same "level" of && or ||.
+ * For example, in the expression 'e1 && (e2 || e3) && (e4 || e5)', the
+ * following operands will be compared:
+ *
+ *	- 'e1', 'e2 || e3', and 'e4 || e5', against each other
+ *	- e2 against e3
+ *	- e4 against e5
+ *
+ * Parentheses are irrelevant within a single level. 'e1 && (e2 && e3)' and
+ * '(e1 && e2) && e3' are both a single level.
+ *
+ * See __expr_eliminate_eq() as well.
+ */
 void expr_eliminate_eq(struct expr **ep1, struct expr **ep2)
 {
 	if (!e1 || !e2)
@@ -197,6 +242,12 @@ void expr_eliminate_eq(struct expr **ep1, struct expr **ep2)
 #undef e1
 #undef e2
 
+/*
+ * Returns true if 'e1' and 'e2' are equal, after minor simplification. Two
+ * &&/|| expressions are considered equal if every operand in one expression
+ * equals some operand in the other (operands do not need to appear in the same
+ * order), recursively.
+ */
 static int expr_eq(struct expr *e1, struct expr *e2)
 {
 	int res, old_count;
@@ -243,6 +294,17 @@ static int expr_eq(struct expr *e1, struct expr *e2)
 	return 0;
 }
 
+/*
+ * Recursively performs the following simplifications in-place (as well as the
+ * corresponding simplifications with swapped operands):
+ *
+ *	expr && n  ->  n
+ *	expr && y  ->  expr
+ *	expr || n  ->  expr
+ *	expr || y  ->  y
+ *
+ * Returns the optimized expression.
+ */
 static struct expr *expr_eliminate_yn(struct expr *e)
 {
 	struct expr *tmp;
@@ -516,12 +578,21 @@ static struct expr *expr_join_and(struct expr *e1, struct expr *e2)
 	return NULL;
 }
 
+/*
+ * expr_eliminate_dups() helper.
+ *
+ * Walks the two expression trees given in 'ep1' and 'ep2'. Any node that does
+ * not have type 'type' (E_OR/E_AND) is considered a leaf, and is compared
+ * against all other leaves to look for simplifications.
+ */
 static void expr_eliminate_dups1(enum expr_type type, struct expr **ep1, struct expr **ep2)
 {
 #define e1 (*ep1)
 #define e2 (*ep2)
 	struct expr *tmp;
 
+	/* Recurse down to leaves */
+
 	if (e1->type == type) {
 		expr_eliminate_dups1(type, &e1->left.expr, &e2);
 		expr_eliminate_dups1(type, &e1->right.expr, &e2);
@@ -532,6 +603,9 @@ static void expr_eliminate_dups1(enum expr_type type, struct expr **ep1, struct
 		expr_eliminate_dups1(type, &e1, &e2->right.expr);
 		return;
 	}
+
+	/* e1 and e2 are leaves. Compare and process them. */
+
 	if (e1 == e2)
 		return;
 
@@ -568,6 +642,17 @@ static void expr_eliminate_dups1(enum expr_type type, struct expr **ep1, struct
 #undef e2
 }
 
+/*
+ * Rewrites 'e' in-place to remove ("join") duplicate and other redundant
+ * operands.
+ *
+ * Example simplifications:
+ *
+ *	A || B || A    ->  A || B
+ *	A && B && A=y  ->  A=y && B
+ *
+ * Returns the deduplicated expression.
+ */
 struct expr *expr_eliminate_dups(struct expr *e)
 {
 	int oldcount;
@@ -584,6 +669,7 @@ struct expr *expr_eliminate_dups(struct expr *e)
 			;
 		}
 		if (!trans_count)
+			/* No simplifications done in this pass. We're done */
 			break;
 		e = expr_eliminate_yn(e);
 	}
@@ -591,6 +677,12 @@ struct expr *expr_eliminate_dups(struct expr *e)
 	return e;
 }
 
+/*
+ * Performs various simplifications involving logical operators and
+ * comparisons.
+ *
+ * Allocates and returns a new expression.
+ */
 struct expr *expr_transform(struct expr *e)
 {
 	struct expr *tmp;
@@ -805,6 +897,20 @@ bool expr_depends_symbol(struct expr *dep, struct symbol *sym)
  	return false;
 }
 
+/*
+ * Inserts explicit comparisons of type 'type' to symbol 'sym' into the
+ * expression 'e'.
+ *
+ * Examples transformations for type == E_UNEQUAL, sym == &symbol_no:
+ *
+ *	A              ->  A!=n
+ *	!A             ->  A=n
+ *	A && B         ->  !(A=n || B=n)
+ *	A || B         ->  !(A=n && B=n)
+ *	A && (B || C)  ->  !(A=n || (B=n && C=n))
+ *
+ * Allocates and returns a new expression.
+ */
 struct expr *expr_trans_compare(struct expr *e, enum expr_type type, struct symbol *sym)
 {
 	struct expr *e1, *e2;
@@ -1073,7 +1179,7 @@ struct expr *expr_simplify_unmet_dep(struct expr *e1, struct expr *e2)
 	return expr_get_leftmost_symbol(ret);
 }
 
-void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken)
+static void __expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken, bool revdep)
 {
 	if (!e) {
 		fn(data, NULL, "y");
@@ -1128,9 +1234,14 @@ void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *
 		fn(data, e->right.sym, e->right.sym->name);
 		break;
 	case E_OR:
-		expr_print(e->left.expr, fn, data, E_OR);
+		if (revdep && e->left.expr->type != E_OR)
-		fn(data, NULL, " || ");
+			fn(data, NULL, "\n  - ");
-		expr_print(e->right.expr, fn, data, E_OR);
+		__expr_print(e->left.expr, fn, data, E_OR, revdep);
+		if (revdep)
+			fn(data, NULL, "\n  - ");
+		else
+			fn(data, NULL, " || ");
+		__expr_print(e->right.expr, fn, data, E_OR, revdep);
 		break;
 	case E_AND:
 		expr_print(e->left.expr, fn, data, E_AND);
@@ -1163,6 +1274,11 @@ void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *
 		fn(data, NULL, ")");
 }
 
+void expr_print(struct expr *e, void (*fn)(void *, struct symbol *, const char *), void *data, int prevtoken)
+{
+	__expr_print(e, fn, data, prevtoken, false);
+}
+
 static void expr_print_file_helper(void *data, struct symbol *sym, const char *str)
 {
 	xfwrite(str, strlen(str), 1, data);
@@ -1207,3 +1323,13 @@ void expr_gstr_print(struct expr *e, struct gstr *gs)
 {
 	expr_print(e, expr_print_gstr_helper, gs, E_NONE);
 }
+
+/*
+ * Transform the top level "||" tokens into newlines and prepend each
+ * line with a minus. This makes expressions much easier to read.
+ * Suitable for reverse dependency expressions.
+ */
+void expr_gstr_print_revdep(struct expr *e, struct gstr *gs)
+{
+	__expr_print(e, expr_print_gstr_helper, gs, E_NONE, true);
+}

scripts/kconfig/expr.h

@@ -74,17 +74,60 @@ enum {
 	S_DEF_COUNT
 };
 
+/*
+ * Represents a configuration symbol.
+ *
+ * Choices are represented as a special kind of symbol and have the
+ * SYMBOL_CHOICE bit set in 'flags'.
+ */
 struct symbol {
+	/* The next symbol in the same bucket in the symbol hash table */
 	struct symbol *next;
+
+	/* The name of the symbol, e.g. "FOO" for 'config FOO' */
 	char *name;
+
+	/* S_BOOLEAN, S_TRISTATE, ... */
 	enum symbol_type type;
+
+	/*
+	 * The calculated value of the symbol. The SYMBOL_VALID bit is set in
+	 * 'flags' when this is up to date. Note that this value might differ
+	 * from the user value set in e.g. a .config file, due to visibility.
+	 */
 	struct symbol_value curr;
+
+	/*
+	 * Values for the symbol provided from outside. def[S_DEF_USER] holds
+	 * the .config value.
+	 */
 	struct symbol_value def[S_DEF_COUNT];
+
+	/*
+	 * An upper bound on the tristate value the user can set for the symbol
+	 * if it is a boolean or tristate. Calculated from prompt dependencies,
+	 * which also inherit dependencies from enclosing menus, choices, and
+	 * ifs. If 'n', the user value will be ignored.
+	 *
+	 * Symbols lacking prompts always have visibility 'n'.
+	 */
 	tristate visible;
+
+	/* SYMBOL_* flags */
 	int flags;
+
+	/* List of properties. See prop_type. */
 	struct property *prop;
+
+	/* Dependencies from enclosing menus, choices, and ifs */
 	struct expr_value dir_dep;
+
+	/* Reverse dependencies through being selected by other symbols */
 	struct expr_value rev_dep;
+
+	/*
+	 * "Weak" reverse dependencies through being implied by other symbols
+	 */
 	struct expr_value implied;
 };
 
@@ -133,7 +176,7 @@ enum prop_type {
 	P_UNKNOWN,
 	P_PROMPT,   /* prompt "foo prompt" or "BAZ Value" */
 	P_COMMENT,  /* text associated with a comment */
-	P_MENU,     /* prompt associated with a menuconfig option */
+	P_MENU,     /* prompt associated with a menu or menuconfig symbol */
 	P_DEFAULT,  /* default y */
 	P_CHOICE,   /* choice value */
 	P_SELECT,   /* select BAR */
@@ -166,22 +209,67 @@ struct property {
 	for (st = sym->prop; st; st = st->next) \
 		if (st->text)
 
+/*
+ * Represents a node in the menu tree, as seen in e.g. menuconfig (though used
+ * for all front ends). Each symbol, menu, etc. defined in the Kconfig files
+ * gets a node. A symbol defined in multiple locations gets one node at each
+ * location.
+ */
 struct menu {
+	/* The next menu node at the same level */
 	struct menu *next;
+
+	/* The parent menu node, corresponding to e.g. a menu or choice */
 	struct menu *parent;
+
+	/* The first child menu node, for e.g. menus and choices */
 	struct menu *list;
+
+	/*
+	 * The symbol associated with the menu node. Choices are implemented as
+	 * a special kind of symbol. NULL for menus, comments, and ifs.
+	 */
 	struct symbol *sym;
+
+	/*
+	 * The prompt associated with the node. This holds the prompt for a
+	 * symbol as well as the text for a menu or comment, along with the
+	 * type (P_PROMPT, P_MENU, etc.)
+	 */
 	struct property *prompt;
+
+	/*
+	 * 'visible if' dependencies. If more than one is given, they will be
+	 * ANDed together.
+	 */
 	struct expr *visibility;
+
+	/*
+	 * Ordinary dependencies from e.g. 'depends on' and 'if', ANDed
+	 * together
+	 */
 	struct expr *dep;
+
+	/* MENU_* flags */
 	unsigned int flags;
+
+	/* Any help text associated with the node */
 	char *help;
+
+	/* The location where the menu node appears in the Kconfig files */
 	struct file *file;
 	int lineno;
+
+	/* For use by front ends that need to store auxiliary data */
 	void *data;
 };
 
+/*
+ * Set on a menu node when the corresponding symbol changes state in some way.
+ * Can be checked by front ends.
+ */
 #define MENU_CHANGED		0x0001
+
 #define MENU_ROOT		0x0002
 
 struct jump_key {
@@ -222,6 +310,7 @@ struct expr *expr_simplify_unmet_dep(struct expr *e1, struct expr *e2);
 void expr_fprint(struct expr *e, FILE *out);
 struct gstr; /* forward */
 void expr_gstr_print(struct expr *e, struct gstr *gs);
+void expr_gstr_print_revdep(struct expr *e, struct gstr *gs);
 
 static inline int expr_is_yes(struct expr *e)
 {

scripts/kconfig/kconf_id.c

@@ -20,7 +20,6 @@ static struct kconf_id kconf_id_array[] = {
 	{ "tristate",		T_TYPE,			TF_COMMAND, S_TRISTATE },
 	{ "def_tristate",	T_DEFAULT,		TF_COMMAND, S_TRISTATE },
 	{ "bool",		T_TYPE,			TF_COMMAND, S_BOOLEAN },
-	{ "boolean",		T_TYPE,			TF_COMMAND, S_BOOLEAN },
 	{ "def_bool",		T_DEFAULT,		TF_COMMAND, S_BOOLEAN },
 	{ "int",		T_TYPE,			TF_COMMAND, S_INT },
 	{ "hex",		T_TYPE,			TF_COMMAND, S_HEX },

scripts/kconfig/lkc.h

@@ -100,7 +100,6 @@ void menu_warn(struct menu *menu, const char *fmt, ...);
 struct menu *menu_add_menu(void);
 void menu_end_menu(void);
 void menu_add_entry(struct symbol *sym);
-void menu_end_entry(void);
 void menu_add_dep(struct expr *dep);
 void menu_add_visibility(struct expr *dep);
 struct property *menu_add_prompt(enum prop_type type, char *prompt, struct expr *dep);

scripts/kconfig/mconf.c

@@ -246,7 +246,7 @@ search_help[] = N_(
 	"  Selected by: BAR [=n]\n"
 	"-----------------------------------------------------------------\n"
 	"o The line 'Type:' shows the type of the configuration option for\n"
-	"  this symbol (boolean, tristate, string, ...)\n"
+	"  this symbol (bool, tristate, string, ...)\n"
 	"o The line 'Prompt:' shows the text used in the menu structure for\n"
 	"  this symbol\n"
 	"o The 'Defined at' line tells at what file / line number the symbol\n"

scripts/kconfig/menu.c

@@ -62,13 +62,8 @@ void menu_add_entry(struct symbol *sym)
 		menu_add_symbol(P_SYMBOL, sym, NULL);
 }
 
-void menu_end_entry(void)
-{
-}
-
 struct menu *menu_add_menu(void)
 {
-	menu_end_entry();
 	last_entry_ptr = &current_entry->list;
 	return current_menu = current_entry;
 }
@@ -79,19 +74,23 @@ void menu_end_menu(void)
 	current_menu = current_menu->parent;
 }
 
-static struct expr *menu_check_dep(struct expr *e)
+/*
+ * Rewrites 'm' to 'm' && MODULES, so that it evaluates to 'n' when running
+ * without modules
+ */
+static struct expr *rewrite_m(struct expr *e)
 {
 	if (!e)
 		return e;
 
 	switch (e->type) {
 	case E_NOT:
-		e->left.expr = menu_check_dep(e->left.expr);
+		e->left.expr = rewrite_m(e->left.expr);
 		break;
 	case E_OR:
 	case E_AND:
-		e->left.expr = menu_check_dep(e->left.expr);
+		e->left.expr = rewrite_m(e->left.expr);
-		e->right.expr = menu_check_dep(e->right.expr);
+		e->right.expr = rewrite_m(e->right.expr);
 		break;
 	case E_SYMBOL:
 		/* change 'm' into 'm' && MODULES */
@@ -106,7 +105,7 @@ static struct expr *menu_check_dep(struct expr *e)
 
 void menu_add_dep(struct expr *dep)
 {
-	current_entry->dep = expr_alloc_and(current_entry->dep, menu_check_dep(dep));
+	current_entry->dep = expr_alloc_and(current_entry->dep, dep);
 }
 
 void menu_set_type(int type)
@@ -131,7 +130,7 @@ static struct property *menu_add_prop(enum prop_type type, char *prompt, struct
 
 	prop->menu = current_entry;
 	prop->expr = expr;
-	prop->visible.expr = menu_check_dep(dep);
+	prop->visible.expr = dep;
 
 	if (prompt) {
 		if (isspace(*prompt)) {
@@ -252,6 +251,16 @@ static void sym_check_prop(struct symbol *sym)
 					    "'%s': number is invalid",
 					    sym->name);
 			}
+			if (sym_is_choice(sym)) {
+				struct property *choice_prop =
+					sym_get_choice_prop(sym2);
+
+				if (!choice_prop ||
+				    prop_get_symbol(choice_prop) != sym)
+					prop_warn(prop,
+						  "choice default symbol '%s' is not contained in the choice",
+						  sym2->name);
+			}
 			break;
 		case P_SELECT:
 		case P_IMPLY:
@@ -260,13 +269,13 @@ static void sym_check_prop(struct symbol *sym)
 			if (sym->type != S_BOOLEAN && sym->type != S_TRISTATE)
 				prop_warn(prop,
 				    "config symbol '%s' uses %s, but is "
-				    "not boolean or tristate", sym->name, use);
+				    "not bool or tristate", sym->name, use);
 			else if (sym2->type != S_UNKNOWN &&
 				 sym2->type != S_BOOLEAN &&
 				 sym2->type != S_TRISTATE)
 				prop_warn(prop,
 				    "'%s' has wrong type. '%s' only "
-				    "accept arguments of boolean and "
+				    "accept arguments of bool and "
 				    "tristate type", sym2->name, use);
 			break;
 		case P_RANGE:
@@ -292,6 +301,11 @@ void menu_finalize(struct menu *parent)
 
 	sym = parent->sym;
 	if (parent->list) {
+		/*
+		 * This menu node has children. We (recursively) process them
+		 * and propagate parent dependencies before moving on.
+		 */
+
 		if (sym && sym_is_choice(sym)) {
 			if (sym->type == S_UNKNOWN) {
 				/* find the first choice value to find out choice type */
@@ -309,30 +323,83 @@ void menu_finalize(struct menu *parent)
 				if (menu->sym && menu->sym->type == S_UNKNOWN)
 					menu_set_type(sym->type);
 			}
+
+			/*
+			 * Use the choice itself as the parent dependency of
+			 * the contained items. This turns the mode of the
+			 * choice into an upper bound on the visibility of the
+			 * choice value symbols.
+			 */
 			parentdep = expr_alloc_symbol(sym);
 		} else if (parent->prompt)
+			/* Menu node for 'menu' */
 			parentdep = parent->prompt->visible.expr;
 		else
+			/* Menu node for 'if' */
 			parentdep = parent->dep;
 
+		/* For each child menu node... */
 		for (menu = parent->list; menu; menu = menu->next) {
-			basedep = expr_transform(menu->dep);
+			/*
+			 * Propagate parent dependencies to the child menu
+			 * node, also rewriting and simplifying expressions
+			 */
+			basedep = rewrite_m(menu->dep);
+			basedep = expr_transform(basedep);
 			basedep = expr_alloc_and(expr_copy(parentdep), basedep);
 			basedep = expr_eliminate_dups(basedep);
 			menu->dep = basedep;
+
 			if (menu->sym)
+				/*
+				 * Note: For symbols, all prompts are included
+				 * too in the symbol's own property list
+				 */
 				prop = menu->sym->prop;
 			else
+				/*
+				 * For non-symbol menu nodes, we just need to
+				 * handle the prompt
+				 */
 				prop = menu->prompt;
+
+			/* For each property... */
 			for (; prop; prop = prop->next) {
 				if (prop->menu != menu)
+					/*
+					 * Two possibilities:
+					 *
+					 * 1. The property lacks dependencies
+					 *    and so isn't location-specific,
+					 *    e.g. an 'option'
+					 *
+					 * 2. The property belongs to a symbol
+					 *    defined in multiple locations and
+					 *    is from some other location. It
+					 *    will be handled there in that
+					 *    case.
+					 *
+					 * Skip the property.
+					 */
 					continue;
-				dep = expr_transform(prop->visible.expr);
+
+				/*
+				 * Propagate parent dependencies to the
+				 * property's condition, rewriting and
+				 * simplifying expressions at the same time
+				 */
+				dep = rewrite_m(prop->visible.expr);
+				dep = expr_transform(dep);
 				dep = expr_alloc_and(expr_copy(basedep), dep);
 				dep = expr_eliminate_dups(dep);
 				if (menu->sym && menu->sym->type != S_TRISTATE)
 					dep = expr_trans_bool(dep);
 				prop->visible.expr = dep;
+
+				/*
+				 * Handle selects and implies, which modify the
+				 * dependencies of the selected/implied symbol
+				 */
 				if (prop->type == P_SELECT) {
 					struct symbol *es = prop_get_symbol(prop);
 					es->rev_dep.expr = expr_alloc_or(es->rev_dep.expr,
@@ -344,34 +411,81 @@ void menu_finalize(struct menu *parent)
 				}
 			}
 		}
+
+		if (sym && sym_is_choice(sym))
+			expr_free(parentdep);
+
+		/*
+		 * Recursively process children in the same fashion before
+		 * moving on
+		 */
 		for (menu = parent->list; menu; menu = menu->next)
 			menu_finalize(menu);
 	} else if (sym) {
+		/*
+		 * Automatic submenu creation. If sym is a symbol and A, B, C,
+		 * ... are consecutive items (symbols, menus, ifs, etc.) that
+		 * all depend on sym, then the following menu structure is
+		 * created:
+		 *
+		 *	sym
+		 *	 +-A
+		 *	 +-B
+		 *	 +-C
+		 *	 ...
+		 *
+		 * This also works recursively, giving the following structure
+		 * if A is a symbol and B depends on A:
+		 *
+		 *	sym
+		 *	 +-A
+		 *	 | +-B
+		 *	 +-C
+		 *	 ...
+		 */
+
 		basedep = parent->prompt ? parent->prompt->visible.expr : NULL;
 		basedep = expr_trans_compare(basedep, E_UNEQUAL, &symbol_no);
 		basedep = expr_eliminate_dups(expr_transform(basedep));
+
+		/* Examine consecutive elements after sym */
 		last_menu = NULL;
 		for (menu = parent->next; menu; menu = menu->next) {
 			dep = menu->prompt ? menu->prompt->visible.expr : menu->dep;
 			if (!expr_contains_symbol(dep, sym))
+				/* No dependency, quit */
 				break;
 			if (expr_depends_symbol(dep, sym))
+				/* Absolute dependency, put in submenu */
 				goto next;
+
+			/*
+			 * Also consider it a dependency on sym if our
+			 * dependencies contain sym and are a "superset" of
+			 * sym's dependencies, e.g. '(sym || Q) && R' when sym
+			 * depends on R.
+			 *
+			 * Note that 'R' might be from an enclosing menu or if,
+			 * making this a more common case than it might seem.
+			 */
 			dep = expr_trans_compare(dep, E_UNEQUAL, &symbol_no);
 			dep = expr_eliminate_dups(expr_transform(dep));
 			dep2 = expr_copy(basedep);
 			expr_eliminate_eq(&dep, &dep2);
 			expr_free(dep);
 			if (!expr_is_yes(dep2)) {
+				/* Not superset, quit */
 				expr_free(dep2);
 				break;
 			}
+			/* Superset, put in submenu */
 			expr_free(dep2);
 		next:
 			menu_finalize(menu);
 			menu->parent = parent;
 			last_menu = menu;
 		}
+		expr_free(basedep);
 		if (last_menu) {
 			parent->list = parent->next;
 			parent->next = last_menu->next;
@@ -420,6 +534,35 @@ void menu_finalize(struct menu *parent)
 			*ep = expr_alloc_one(E_LIST, NULL);
 			(*ep)->right.sym = menu->sym;
 		}
+
+		/*
+		 * This code serves two purposes:
+		 *
+		 * (1) Flattening 'if' blocks, which do not specify a submenu
+		 *     and only add dependencies.
+		 *
+		 *     (Automatic submenu creation might still create a submenu
+		 *     from an 'if' before this code runs.)
+		 *
+		 * (2) "Undoing" any automatic submenus created earlier below
+		 *     promptless symbols.
+		 *
+		 * Before:
+		 *
+		 *	A
+		 *	if ... (or promptless symbol)
+		 *	 +-B
+		 *	 +-C
+		 *	D
+		 *
+		 * After:
+		 *
+		 *	A
+		 *	if ... (or promptless symbol)
+		 *	B
+		 *	C
+		 *	D
+		 */
 		if (menu->list && (!menu->prompt || !menu->prompt->text)) {
 			for (last_menu = menu->list; ; last_menu = last_menu->next) {
 				last_menu->parent = parent;
@@ -444,6 +587,15 @@ void menu_finalize(struct menu *parent)
 		sym->flags |= SYMBOL_WARNED;
 	}
 
+	/*
+	 * For non-optional choices, add a reverse dependency (corresponding to
+	 * a select) of '<visibility> && m'. This prevents the user from
+	 * setting the choice mode to 'n' when the choice is visible.
+	 *
+	 * This would also work for non-choice symbols, but only non-optional
+	 * choices clear SYMBOL_OPTIONAL as of writing. Choices are implemented
+	 * as a type of symbol.
+	 */
 	if (sym && !sym_is_optional(sym) && parent->prompt) {
 		sym->rev_dep.expr = expr_alloc_or(sym->rev_dep.expr,
 				expr_alloc_and(parent->prompt->visible.expr,
@@ -676,14 +828,14 @@ static void get_symbol_str(struct gstr *r, struct symbol *sym,
 	get_symbol_props_str(r, sym, P_SELECT, _("  Selects: "));
 	if (sym->rev_dep.expr) {
 		str_append(r, _("  Selected by: "));
-		expr_gstr_print(sym->rev_dep.expr, r);
+		expr_gstr_print_revdep(sym->rev_dep.expr, r);
 		str_append(r, "\n");
 	}
 
 	get_symbol_props_str(r, sym, P_IMPLY, _("  Implies: "));
 	if (sym->implied.expr) {
 		str_append(r, _("  Implied by: "));
-		expr_gstr_print(sym->implied.expr, r);
+		expr_gstr_print_revdep(sym->implied.expr, r);
 		str_append(r, "\n");
 	}
 

scripts/kconfig/symbol.c

@@ -77,7 +77,7 @@ const char *sym_type_name(enum symbol_type type)
 {
 	switch (type) {
 	case S_BOOLEAN:
-		return "boolean";
+		return "bool";
 	case S_TRISTATE:
 		return "tristate";
 	case S_INT:
@@ -907,6 +907,10 @@ const char *sym_expand_string_value(const char *in)
 	char *res;
 	size_t reslen;
 
+	/*
+	 * 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';
@@ -1150,8 +1154,7 @@ static void sym_check_print_recursive(struct symbol *last_sym)
 		if (stack->sym == last_sym)
 			fprintf(stderr, "%s:%d:error: recursive dependency detected!\n",
 				prop->file->name, prop->lineno);
-			fprintf(stderr, "For a resolution refer to Documentation/kbuild/kconfig-language.txt\n");
+
-			fprintf(stderr, "subsection \"Kconfig recursive dependency limitations\"\n");
 		if (stack->expr) {
 			fprintf(stderr, "%s:%d:\tsymbol %s %s value contains %s\n",
 				prop->file->name, prop->lineno,
@@ -1181,6 +1184,11 @@ static void sym_check_print_recursive(struct symbol *last_sym)
 		}
 	}
 
+	fprintf(stderr,
+		"For a resolution refer to Documentation/kbuild/kconfig-language.txt\n"
+		"subsection \"Kconfig recursive dependency limitations\"\n"
+		"\n");
+
 	if (check_top == &cv_stack)
 		dep_stack_remove();
 }

scripts/kconfig/zconf.l

@@ -106,11 +106,11 @@ n	[A-Za-z0-9_-]
 		current_pos.file = current_file;
 		current_pos.lineno = current_file->lineno;
 		if (id && id->flags & TF_COMMAND) {
-			zconflval.id = id;
+			yylval.id = id;
 			return id->token;
 		}
 		alloc_string(yytext, yyleng);
-		zconflval.string = text;
+		yylval.string = text;
 		return T_WORD;
 	}
 	.	warn_ignored_character(*yytext);
@@ -142,11 +142,11 @@ n	[A-Za-z0-9_-]
 	({n}|[/.])+	{
 		const struct kconf_id *id = kconf_id_lookup(yytext, yyleng);
 		if (id && id->flags & TF_PARAM) {
-			zconflval.id = id;
+			yylval.id = id;
 			return id->token;
 		}
 		alloc_string(yytext, yyleng);
-		zconflval.string = text;
+		yylval.string = text;
 		return T_WORD;
 	}
 	#.*	/* comment */
@@ -161,7 +161,7 @@ n	[A-Za-z0-9_-]
 <STRING>{
 	[^'"\\\n]+/\n	{
 		append_string(yytext, yyleng);
-		zconflval.string = text;
+		yylval.string = text;
 		return T_WORD_QUOTE;
 	}
 	[^'"\\\n]+	{
@@ -169,7 +169,7 @@ n	[A-Za-z0-9_-]
 	}
 	\\.?/\n	{
 		append_string(yytext + 1, yyleng - 1);
-		zconflval.string = text;
+		yylval.string = text;
 		return T_WORD_QUOTE;
 	}
 	\\.?	{
@@ -178,7 +178,7 @@ n	[A-Za-z0-9_-]
 	\'|\"	{
 		if (str == yytext[0]) {
 			BEGIN(PARAM);
-			zconflval.string = text;
+			yylval.string = text;
 			return T_WORD_QUOTE;
 		} else
 			append_string(yytext, 1);
@@ -261,7 +261,7 @@ void zconf_starthelp(void)
 
 static void zconf_endhelp(void)
 {
-	zconflval.string = text;
+	yylval.string = text;
 	BEGIN(INITIAL);
 }
 

scripts/kconfig/zconf.y

@@ -20,10 +20,10 @@
 
 int cdebug = PRINTD;
 
-extern int zconflex(void);
+int yylex(void);
+static void yyerror(const char *err);
 static void zconfprint(const char *err, ...);
 static void zconf_error(const char *err, ...);
-static void zconferror(const char *err);
 static bool zconf_endtoken(const struct kconf_id *id, int starttoken, int endtoken);
 
 struct symbol *symbol_hash[SYMBOL_HASHSIZE];
@@ -85,6 +85,7 @@ static struct menu *current_menu, *current_entry;
 %nonassoc T_NOT
 
 %type <string> prompt
+%type <symbol> nonconst_symbol
 %type <symbol> symbol
 %type <expr> expr
 %type <expr> if_expr
@@ -101,14 +102,34 @@ static struct menu *current_menu, *current_entry;
 } if_entry menu_entry choice_entry
 
 %{
-/* Include zconf_id.c here so it can see the token constants. */
+/* Include kconf_id.c here so it can see the token constants. */
 #include "kconf_id.c"
 %}
 
 %%
 input: nl start | start;
 
-start: mainmenu_stmt stmt_list | stmt_list;
+start: mainmenu_stmt stmt_list | no_mainmenu_stmt stmt_list;
+
+/* mainmenu entry */
+
+mainmenu_stmt: T_MAINMENU prompt nl
+{
+	menu_add_prompt(P_MENU, $2, NULL);
+};
+
+/* Default main menu, if there's no mainmenu entry */
+
+no_mainmenu_stmt: /* empty */
+{
+	/*
+	 * Hack: Keep the main menu title on the heap so we can safely free it
+	 * later regardless of whether it comes from the 'prompt' in
+	 * mainmenu_stmt or here
+	 */
+	menu_add_prompt(P_MENU, strdup("Linux Kernel Configuration"), NULL);
+};
+
 
 stmt_list:
 	  /* empty */
@@ -145,26 +166,23 @@ option_error:
 
 /* config/menuconfig entry */
 
-config_entry_start: T_CONFIG T_WORD T_EOL
+config_entry_start: T_CONFIG nonconst_symbol T_EOL
 {
-	struct symbol *sym = sym_lookup($2, 0);
+	$2->flags |= SYMBOL_OPTIONAL;
-	sym->flags |= SYMBOL_OPTIONAL;
+	menu_add_entry($2);
-	menu_add_entry(sym);
+	printd(DEBUG_PARSE, "%s:%d:config %s\n", zconf_curname(), zconf_lineno(), $2->name);
-	printd(DEBUG_PARSE, "%s:%d:config %s\n", zconf_curname(), zconf_lineno(), $2);
 };
 
 config_stmt: config_entry_start config_option_list
 {
-	menu_end_entry();
 	printd(DEBUG_PARSE, "%s:%d:endconfig\n", zconf_curname(), zconf_lineno());
 };
 
-menuconfig_entry_start: T_MENUCONFIG T_WORD T_EOL
+menuconfig_entry_start: T_MENUCONFIG nonconst_symbol T_EOL
 {
-	struct symbol *sym = sym_lookup($2, 0);
+	$2->flags |= SYMBOL_OPTIONAL;
-	sym->flags |= SYMBOL_OPTIONAL;
+	menu_add_entry($2);
-	menu_add_entry(sym);
+	printd(DEBUG_PARSE, "%s:%d:menuconfig %s\n", zconf_curname(), zconf_lineno(), $2->name);
-	printd(DEBUG_PARSE, "%s:%d:menuconfig %s\n", zconf_curname(), zconf_lineno(), $2);
 };
 
 menuconfig_stmt: menuconfig_entry_start config_option_list
@@ -173,7 +191,6 @@ menuconfig_stmt: menuconfig_entry_start config_option_list
 		current_entry->prompt->type = P_MENU;
 	else
 		zconfprint("warning: menuconfig statement without prompt");
-	menu_end_entry();
 	printd(DEBUG_PARSE, "%s:%d:endconfig\n", zconf_curname(), zconf_lineno());
 };
 
@@ -211,15 +228,15 @@ config_option: T_DEFAULT expr if_expr T_EOL
 		$1->stype);
 };
 
-config_option: T_SELECT T_WORD if_expr T_EOL
+config_option: T_SELECT nonconst_symbol if_expr T_EOL
 {
-	menu_add_symbol(P_SELECT, sym_lookup($2, 0), $3);
+	menu_add_symbol(P_SELECT, $2, $3);
 	printd(DEBUG_PARSE, "%s:%d:select\n", zconf_curname(), zconf_lineno());
 };
 
-config_option: T_IMPLY T_WORD if_expr T_EOL
+config_option: T_IMPLY nonconst_symbol if_expr T_EOL
 {
-	menu_add_symbol(P_IMPLY, sym_lookup($2, 0), $3);
+	menu_add_symbol(P_IMPLY, $2, $3);
 	printd(DEBUG_PARSE, "%s:%d:imply\n", zconf_curname(), zconf_lineno());
 };
 
@@ -237,8 +254,10 @@ symbol_option_list:
 	| symbol_option_list T_WORD symbol_option_arg
 {
 	const struct kconf_id *id = kconf_id_lookup($2, strlen($2));
-	if (id && id->flags & TF_OPTION)
+	if (id && id->flags & TF_OPTION) {
 		menu_add_option(id->token, $3);
+		free($3);
+	}
 	else
 		zconfprint("warning: ignoring unknown option %s", $2);
 	free($2);
@@ -308,10 +327,10 @@ choice_option: T_OPTIONAL T_EOL
 	printd(DEBUG_PARSE, "%s:%d:optional\n", zconf_curname(), zconf_lineno());
 };
 
-choice_option: T_DEFAULT T_WORD if_expr T_EOL
+choice_option: T_DEFAULT nonconst_symbol if_expr T_EOL
 {
 	if ($1->stype == S_UNKNOWN) {
-		menu_add_symbol(P_DEFAULT, sym_lookup($2, 0), $3);
+		menu_add_symbol(P_DEFAULT, $2, $3);
 		printd(DEBUG_PARSE, "%s:%d:default\n",
 			zconf_curname(), zconf_lineno());
 	} else
@@ -351,13 +370,6 @@ if_block:
 	| if_block choice_stmt
 ;
 
-/* mainmenu entry */
-
-mainmenu_stmt: T_MAINMENU prompt nl
-{
-	menu_add_prompt(P_MENU, $2, NULL);
-};
-
 /* menu entry */
 
 menu: T_MENU prompt T_EOL
@@ -394,6 +406,7 @@ source_stmt: T_SOURCE prompt T_EOL
 {
 	printd(DEBUG_PARSE, "%s:%d:source %s\n", zconf_curname(), zconf_lineno(), $2);
 	zconf_nextfile($2);
+	free($2);
 };
 
 /* comment entry */
@@ -406,9 +419,7 @@ comment: T_COMMENT prompt T_EOL
 };
 
 comment_stmt: comment depends_list
-{
+;
-	menu_end_entry();
-};
 
 /* help option */
 
@@ -420,6 +431,11 @@ help_start: T_HELP T_EOL
 
 help: help_start T_HELPTEXT
 {
+	if (current_entry->help) {
+		free(current_entry->help);
+		zconfprint("warning: '%s' defined with more than one help text -- only the last one will be used",
+			   current_entry->sym->name ?: "<choice>");
+	}
 	current_entry->help = $2;
 };
 
@@ -491,7 +507,10 @@ expr:	  symbol				{ $$ = expr_alloc_symbol($1); }
 	| expr T_AND expr			{ $$ = expr_alloc_two(E_AND, $1, $3); }
 ;
 
-symbol:	  T_WORD	{ $$ = sym_lookup($1, 0); free($1); }
+/* For symbol definitions, selects, etc., where quotes are not accepted */
+nonconst_symbol: T_WORD { $$ = sym_lookup($1, 0); free($1); };
+
+symbol:	  nonconst_symbol
 	| T_WORD_QUOTE	{ $$ = sym_lookup($1, SYMBOL_CONST); free($1); }
 ;
 
@@ -502,6 +521,7 @@ word_opt: /* empty */			{ $$ = NULL; }
 
 void conf_parse(const char *name)
 {
+	const char *tmp;
 	struct symbol *sym;
 	int i;
 
@@ -509,25 +529,26 @@ void conf_parse(const char *name)
 
 	sym_init();
 	_menu_init();
-	rootmenu.prompt = menu_add_prompt(P_MENU, "Linux Kernel Configuration", NULL);
 
 	if (getenv("ZCONF_DEBUG"))
-		zconfdebug = 1;
+		yydebug = 1;
-	zconfparse();
+	yyparse();
-	if (zconfnerrs)
+	if (yynerrs)
 		exit(1);
 	if (!modules_sym)
 		modules_sym = sym_find( "n" );
 
+	tmp = rootmenu.prompt->text;
 	rootmenu.prompt->text = _(rootmenu.prompt->text);
 	rootmenu.prompt->text = sym_expand_string_value(rootmenu.prompt->text);
+	free((char*)tmp);
 
 	menu_finalize(&rootmenu);
 	for_all_symbols(i, sym) {
 		if (sym_check_deps(sym))
-			zconfnerrs++;
+			yynerrs++;
 	}
-	if (zconfnerrs)
+	if (yynerrs)
 		exit(1);
 	sym_set_change_count(1);
 }
@@ -552,7 +573,7 @@ static bool zconf_endtoken(const struct kconf_id *id, int starttoken, int endtok
 	if (id->token != endtoken) {
 		zconf_error("unexpected '%s' within %s block",
 			id->name, zconf_tokenname(starttoken));
-		zconfnerrs++;
+		yynerrs++;
 		return false;
 	}
 	if (current_menu->file != current_file) {
@@ -561,7 +582,7 @@ static bool zconf_endtoken(const struct kconf_id *id, int starttoken, int endtok
 		fprintf(stderr, "%s:%d: location of the '%s'\n",
 			current_menu->file->name, current_menu->lineno,
 			zconf_tokenname(starttoken));
-		zconfnerrs++;
+		yynerrs++;
 		return false;
 	}
 	return true;
@@ -582,7 +603,7 @@ static void zconf_error(const char *err, ...)
 {
 	va_list ap;
 
-	zconfnerrs++;
+	yynerrs++;
 	fprintf(stderr, "%s:%d: ", zconf_curname(), zconf_lineno());
 	va_start(ap, err);
 	vfprintf(stderr, err, ap);
@@ -590,7 +611,7 @@ static void zconf_error(const char *err, ...)
 	fprintf(stderr, "\n");
 }
 
-static void zconferror(const char *err)
+static void yyerror(const char *err)
 {
 	fprintf(stderr, "%s:%d: %s\n", zconf_curname(), zconf_lineno() + 1, err);
 }
@@ -623,7 +644,7 @@ static void print_symbol(FILE *out, struct menu *menu)
 		fprintf(out, "\nconfig %s\n", sym->name);
 	switch (sym->type) {
 	case S_BOOLEAN:
-		fputs("  boolean\n", out);
+		fputs("  bool\n", out);
 		break;
 	case S_TRISTATE:
 		fputs("  tristate\n", out);