kconfig: Sync with upstream v4.16

This commit introduces the following upstream changes:

5ae6fcc4bb82 kconfig: fix line number in recursive inclusion error message
1a90ce36c6ef kconfig: Update ncurses package names for menuconfig
bf0bbdcf1003 kconfig: Don't leak choice names during parsing
f4bc1eefc160 kconfig: set SYMBOL_AUTO to the symbol marked with defconfig_list
cd81fc82b93f kconfig: add xstrdup() helper
523ca58b7db2 kconfig: remove const qualifier from sym_expand_string_value()
d717f24d8c68 kconfig: add xrealloc() helper
9e3e10c72536 kconfig: send error messages to stderr
f3ff6fb5db68 kconfig: echo stdin to stdout if either is redirected
d2a04648a5db kconfig: remove check_stdin()
cd58a91def2a kconfig: remove 'config*' pattern from .gitignnore
4f208f392103 kconfig: show '?' prompt even if no help text is available
cb67ab2cd2b8 kconfig: do not write choice values when their dependency becomes n
1b9eda2e4892 kconfig: Warn if help text is blank
cedd55d49dee kconfig: Remove silentoldconfig from help and docs; fix kconfig/conf's help
1ccb27143360 kconfig: make "Selected by:" and "Implied by:" readable
312ee68752fa kconfig: announce removal of oldnoconfig if used
d0fd0428ecf0 kconfig: fix make xconfig when gettext is missing
b53688014e33 kconfig: Clarify menu and 'if' dependency propagation
9d1a9e8bc18b kconfig: Document 'if' flattening logic
d3465af60f44 kconfig: Clarify choice dependency propagation
3e41ba05b6d6 kconfig: Document SYMBOL_OPTIONAL logic
765f4cdef6f8 kconfig: use default 'yy' prefix for lexer and parser
84dd95d4f87a kconfig: make conf_unsaved a local variable of conf_read()
5a3dc717b3c7 kconfig: make xfgets() really static
52e58a3caeba kconfig: make input_mode static
6479f327dea6 kconfig: Warn if there is more than one help text
b92d804a5179 kconfig: drop 'boolean' keyword
df60f4b92d3d kconfig: Remove menu_end_entry()
0735f7e5def2 kconfig: Document important expression functions
05cccce58045 kconfig: Document automatic submenu creation code
7cf33f88e294 kconfig: Fix choice symbol expression leak
5b1374b3b3c2 kconfig: Fix expr_free() E_NOT leak
ae7440ef0c80 kconfig: Fix automatic menu creation mem leak
0724a7c32a54 kconfig: Don't leak main menus during parsing
bc28fe1d5ede kconfig: Don't leak 'option' arguments during parsing
24161a6711c9 kconfig: Don't leak 'source' filenames during parsing
26e47a3c11a2 kconfig: Don't leak symbol names during parsing
29c833061c1d kconfig: generate lexer and parser during build instead of shipping
e3b03bf29d6b kconfig: display recursive dependency resolution hint just once
f77850d3fe0c kconfig: Clean up modules handling and fix crash
fa8cedaef814 kconfig: Clarify expression rewriting
9a826842ff2f kconfig: Rename menu_check_dep() to rewrite_m()
c873443430eb kconfig: Sync zconf.y with zconf.tab.c_shipped
52aede4ba5ef kconfig: Document the 'symbol' struct
33ca1a248663 kconfig: Document the 'menu' struct
2c37e08464a8 kconfig: Warn if choice default is not in choice

Signed-off-by: Chris Packham <judge.packham@gmail.com>

17 files changed, 575 insertions, 168 deletions

diff --git a/kconfig/.gitignore b/kconfig/.gitignore
index 69967bc..0c8d3a2 100644
--- a/kconfig/.gitignore
+++ b/kconfig/.gitignore
@@ -1,9 +1,15 @@
-conf
-?conf
-*.o
+#
+# Generated files
+#
+*.lex.c
+*.tab.c
+*.tab.h
 .deps
-zconf.c
-zconf.lex.c
-*.exe
 Makefile
-.dirstamp
+
+#
+# configuration programs
+#
+conf
+mconf
+nconf
diff --git a/kconfig/check.sh b/kconfig/check.sh
index 97f0fee..97f0fee 100644..100755
--- a/kconfig/check.sh
+++ b/kconfig/check.sh
diff --git a/kconfig/conf.c b/kconfig/conf.c
index df87eb4..55e4f7c 100644
--- a/kconfig/conf.c
+++ b/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,
@@ -35,11 +34,11 @@ enum input_mode {
 	savedefconfig,
 	listnewconfig,
 	olddefconfig,
-} input_mode = oldaskconfig;
+};
+static enum input_mode input_mode = oldaskconfig;
 
 static int indent = 1;
 static int tty_stdio;
-static int valid_stdin = 1;
 static int sync_kconfig;
 static int conf_cnt;
 static char line[PATH_MAX];
@@ -72,14 +71,14 @@ static void strip(char *str)
 		*p-- = 0;
 }
 
-static void check_stdin(void)
+/* Helper function to facilitate fgets() by Jean Sacren. */
+static void xfgets(char *str, int size, FILE *in)
 {
-	if (!valid_stdin) {
-		/* For crosstool-NG, we don't care if stdin/stdout got redirected.
-		 * In this case, just printf a cariage return, for pretty output.
-		 */
-		printf("\n");
-	}
+	if (!fgets(str, size, in))
+		fprintf(stderr, "\nError in reading or end of file.\n");
+
+	if (!tty_stdio)
+		printf("%s", str);
 }
 
 static int conf_askvalue(struct symbol *sym, const char *def)
@@ -106,13 +105,10 @@ static int conf_askvalue(struct symbol *sym, const char *def)
 			printf("%s\n", def);
 			return 0;
 		}
-		check_stdin();
 		/* fall through */
 	case oldaskconfig:
 		fflush(stdout);
 		xfgets(line, sizeof(line), stdin);
-		if (!tty_stdio)
-			printf("\n");
 		return 1;
 	default:
 		break;
@@ -192,9 +188,7 @@ static int conf_sym(struct menu *menu)
 			printf("/m");
 		if (oldval != yes && sym_tristate_within_range(sym, yes))
 			printf("/y");
-		if (menu_has_help(menu))
-			printf("/?");
-		printf("] ");
+		printf("/?] ");
 		if (!conf_askvalue(sym, sym_get_string_value(sym)))
 			return 0;
 		strip(line);
@@ -296,10 +290,7 @@ static int conf_choice(struct menu *menu)
 			printf("[1]: 1\n");
 			goto conf_childs;
 		}
-		printf("[1-%d", cnt);
-		if (menu_has_help(menu))
-			printf("?");
-		printf("]: ");
+		printf("[1-%d?]: ", cnt);
 		switch (input_mode) {
 		case oldconfig:
 		case silentoldconfig:
@@ -308,7 +299,6 @@ static int conf_choice(struct menu *menu)
 				printf("%d\n", cnt);
 				break;
 			}
-			check_stdin();
 			/* fall through */
 		case oldaskconfig:
 			fflush(stdout);
@@ -480,7 +470,7 @@ int main(int ac, char **av)
 	bindtextdomain(PACKAGE, LOCALEDIR);
 	textdomain(PACKAGE);
 
-	tty_stdio = isatty(0) && isatty(1) && isatty(2);
+	tty_stdio = isatty(0) && isatty(1);
 
 	while ((opt = getopt_long(ac, av, "s", long_opts, NULL)) != -1) {
 		if (opt == 's') {
@@ -537,7 +527,7 @@ int main(int ac, char **av)
 		}
 	}
 	if (ac == optind) {
-		printf(_("%s: Kconfig file missing\n"), av[0]);
+		fprintf(stderr, _("%s: Kconfig file missing\n"), av[0]);
 		fprintf(stderr, _("See README for usage info\n"));
 		exit(1);
 	}
@@ -562,9 +552,11 @@ int main(int ac, char **av)
 		if (!defconfig_file)
 			defconfig_file = conf_get_default_confname();
 		if (conf_read(defconfig_file)) {
-			printf(_("***\n"
-				"*** Can't find default configuration \"%s\"!\n"
-				"***\n"), defconfig_file);
+			fprintf(stderr,
+				_("***\n"
+				  "*** Can't find default configuration \"%s\"!\n"
+				  "***\n"),
+				defconfig_file);
 			exit(1);
 		}
 		break;
@@ -622,7 +614,6 @@ int main(int ac, char **av)
 				return 1;
 			}
 		}
-		valid_stdin = tty_stdio;
 	}
 
 	switch (input_mode) {
@@ -693,12 +684,3 @@ 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");
-}
diff --git a/kconfig/confdata.c b/kconfig/confdata.c
index 297b079..df26c7b 100644
--- a/kconfig/confdata.c
+++ b/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";
 
@@ -178,7 +178,7 @@ static int conf_set_sym_val(struct symbol *sym, int def, int def_flags, char *p)
 	case S_HEX:
 	done:
 		if (sym_string_valid(sym, p)) {
-			sym->def[def].val = strdup(p);
+			sym->def[def].val = xstrdup(p);
 			sym->flags |= def_flags;
 		} else {
 			if (def != S_DEF_AUTO)
@@ -201,7 +201,7 @@ static int add_byte(int c, char **lineptr, size_t slen, size_t *n)
 	if (new_size > *n) {
 		new_size += LINE_GROWTH - 1;
 		new_size *= 2;
-		nline = realloc(*lineptr, new_size);
+		nline = xrealloc(*lineptr, new_size);
 		if (!nline)
 			return -1;
 
@@ -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
 					 */
diff --git a/kconfig/expr.c b/kconfig/expr.c
index 8cee597..d453819 100644
--- a/kconfig/expr.c
+++ b/kconfig/expr.c
@@ -94,7 +94,7 @@ struct expr *expr_copy(const struct expr *org)
 		e->right.expr = expr_copy(org->right.expr);
 		break;
 	default:
-		printf("can't copy type %d\n", e->type);
+		fprintf(stderr, "can't copy type %d\n", e->type);
 		free(e);
 		e = NULL;
 		break;
@@ -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:
@@ -127,7 +127,7 @@ void expr_free(struct expr *e)
 		expr_free(e->right.expr);
 		break;
 	default:
-		printf("how to free type %d?\n", e->type);
+		fprintf(stderr, "how to free type %d?\n", e->type);
 		break;
 	}
 	free(e);
@@ -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);
-		fn(data, NULL, " || ");
-		expr_print(e->right.expr, fn, data, E_OR);
+		if (revdep && e->left.expr->type != E_OR)
+			fn(data, NULL, "\n  - ");
+		__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);
+}
diff --git a/kconfig/expr.h b/kconfig/expr.h
index a73f762..c16e82e 100644
--- a/kconfig/expr.h
+++ b/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)
 {
diff --git a/kconfig/kconf_id.c b/kconfig/kconf_id.c
index 5abbc72..3ea9c5f 100644
--- a/kconfig/kconf_id.c
+++ b/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 },
diff --git a/kconfig/lkc.h b/kconfig/lkc.h
index cdcbe43..2d5ec2d 100644
--- a/kconfig/lkc.h
+++ b/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);
@@ -115,6 +114,8 @@ struct file *file_lookup(const char *name);
 int file_write_dep(const char *name);
 void *xmalloc(size_t size);
 void *xcalloc(size_t nmemb, size_t size);
+void *xrealloc(void *p, size_t size);
+char *xstrdup(const char *s);
 
 struct gstr {
 	size_t len;
diff --git a/kconfig/lkc_proto.h b/kconfig/lkc_proto.h
index 5d86e2d..9dc8abf 100644
--- a/kconfig/lkc_proto.h
+++ b/kconfig/lkc_proto.h
@@ -31,7 +31,7 @@ extern struct symbol * symbol_hash[SYMBOL_HASHSIZE];
 
 struct symbol * sym_lookup(const char *name, int flags);
 struct symbol * sym_find(const char *name);
-const char * sym_expand_string_value(const char *in);
+char *sym_expand_string_value(const char *in);
 const char * sym_escape_string_value(const char *in);
 struct symbol ** sym_re_search(const char *pattern);
 const char * sym_type_name(enum symbol_type type);
diff --git a/kconfig/lxdialog/check-lxdialog.sh b/kconfig/lxdialog/check-lxdialog.sh
index a10bd9d..6c0bcd9 100644..100755
--- a/kconfig/lxdialog/check-lxdialog.sh
+++ b/kconfig/lxdialog/check-lxdialog.sh
@@ -55,7 +55,8 @@ EOF
 	    echo " *** required header files."                            1>&2
 	    echo " *** 'make menuconfig' requires the ncurses libraries." 1>&2
 	    echo " *** "                                                  1>&2
-	    echo " *** Install ncurses (ncurses-devel) and try again."    1>&2
+	    echo " *** Install ncurses (ncurses-devel or libncurses-dev " 1>&2
+	    echo " *** depending on your distribution) and try again."    1>&2
 	    echo " *** "                                                  1>&2
 	    exit 1
 	fi
diff --git a/kconfig/mconf.c b/kconfig/mconf.c
index dc7421c..ea50ba0 100644
--- a/kconfig/mconf.c
+++ b/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"
diff --git a/kconfig/menu.c b/kconfig/menu.c
index 1fd7b25..d5a3322 100644
--- a/kconfig/menu.c
+++ b/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->right.expr = menu_check_dep(e->right.expr);
+		e->left.expr = rewrite_m(e->left.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) {
 		/* For crostool-NG, a leading pipe followed with spaces
@@ -219,6 +218,7 @@ void menu_add_option(int token, char *arg)
 			sym_defconfig_list = current_entry->sym;
 		else if (sym_defconfig_list != current_entry->sym)
 			zconf_error("trying to redefine defconfig symbol");
+		sym_defconfig_list->flags |= SYMBOL_AUTO;
 		break;
 	case T_OPT_ENV:
 		prop_add_env(arg);
@@ -258,6 +258,16 @@ 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:
@@ -266,13 +276,13 @@ 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:
@@ -298,6 +308,11 @@ 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 */
@@ -315,30 +330,83 @@ 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,
@@ -350,34 +418,81 @@ 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;
@@ -426,6 +541,35 @@ 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;
@@ -450,6 +594,15 @@ 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,
@@ -682,14 +835,14 @@ 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");
 	}
 
diff --git a/kconfig/nconf.gui.c b/kconfig/nconf.gui.c
index a64b1c3..88874ac 100644
--- a/kconfig/nconf.gui.c
+++ b/kconfig/nconf.gui.c
@@ -6,6 +6,7 @@
  *
  */
 #include "nconf.h"
+#include "lkc.h"
 
 /* a list of all the different widgets we use */
 attributes_t attributes[ATTR_MAX+1] = {0};
@@ -374,7 +375,7 @@ int dialog_inputbox(WINDOW *main_window,
 
 	if (strlen(init)+1 > *result_len) {
 		*result_len = strlen(init)+1;
-		*resultp = result = realloc(result, *result_len);
+		*resultp = result = xrealloc(result, *result_len);
 	}
 
 	/* find the widest line of msg: */
diff --git a/kconfig/symbol.c b/kconfig/symbol.c
index 35e0937..2220bc4 100644
--- a/kconfig/symbol.c
+++ b/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:
@@ -183,7 +183,7 @@ static void sym_validate_range(struct symbol *sym)
 		sprintf(str, "%lld", val2);
 	else
 		sprintf(str, "0x%llx", val2);
-	sym->curr.val = strdup(str);
+	sym->curr.val = xstrdup(str);
 }
 
 static void sym_set_changed(struct symbol *sym)
@@ -371,11 +371,13 @@ void sym_calc_value(struct symbol *sym)
 		sym->curr.tri = no;
 		return;
 	}
-	if (!sym_is_choice_value(sym))
-		sym->flags &= ~SYMBOL_WRITE;
+	sym->flags &= ~SYMBOL_WRITE;
 
 	sym_calc_visibility(sym);
 
+	if (sym->visible != no)
+		sym->flags |= SYMBOL_WRITE;
+
 	/* set default if recursively called */
 	sym->curr = newval;
 
@@ -390,7 +392,6 @@ void sym_calc_value(struct symbol *sym)
 				/* if the symbol is visible use the user value
 				 * if available, otherwise try the default value
 				 */
-				sym->flags |= SYMBOL_WRITE;
 				if (sym_has_value(sym)) {
 					newval.tri = EXPR_AND(sym->def[S_DEF_USER].tri,
 							      sym->visible);
@@ -433,12 +434,9 @@ void sym_calc_value(struct symbol *sym)
 	case S_STRING:
 	case S_HEX:
 	case S_INT:
-		if (sym->visible != no) {
-			sym->flags |= SYMBOL_WRITE;
-			if (sym_has_value(sym)) {
-				newval.val = sym->def[S_DEF_USER].val;
-				break;
-			}
+		if (sym->visible != no && sym_has_value(sym)) {
+			newval.val = sym->def[S_DEF_USER].val;
+			break;
 		}
 		prop = sym_get_default_prop(sym);
 		if (prop) {
@@ -851,7 +849,7 @@ struct symbol *sym_lookup(const char *name, int flags)
 				   : !(symbol->flags & (SYMBOL_CONST|SYMBOL_CHOICE))))
 				return symbol;
 		}
-		new_name = strdup(name);
+		new_name = xstrdup(name);
 	} else {
 		new_name = NULL;
 		hash = 0;
@@ -901,12 +899,16 @@ struct symbol *sym_find(const char *name)
  * name to be expanded shall be prefixed by a '$'. Unknown symbol expands to
  * the empty string.
  */
-const char *sym_expand_string_value(const char *in)
+char *sym_expand_string_value(const char *in)
 {
 	const char *src;
 	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';
@@ -934,7 +936,7 @@ const char *sym_expand_string_value(const char *in)
 		newlen = strlen(res) + strlen(symval) + strlen(src) + 1;
 		if (newlen > reslen) {
 			reslen = newlen;
-			res = realloc(res, reslen);
+			res = xrealloc(res, reslen);
 		}
 
 		strcat(res, symval);
@@ -1219,7 +1221,7 @@ static struct symbol *sym_check_expr_deps(struct expr *e)
 	default:
 		break;
 	}
-	printf("Oops! How to check %d?\n", e->type);
+	fprintf(stderr, "Oops! How to check %d?\n", e->type);
 	return NULL;
 }
 
diff --git a/kconfig/util.c b/kconfig/util.c
index 0e76042..c6f6e21 100644
--- a/kconfig/util.c
+++ b/kconfig/util.c
@@ -14,11 +14,11 @@
 struct file *file_lookup(const char *name)
 {
 	struct file *file;
-	const char *file_name = sym_expand_string_value(name);
+	char *file_name = sym_expand_string_value(name);
 
 	for (file = file_list; file; file = file->next) {
 		if (!strcmp(name, file->name)) {
-			free((void *)file_name);
+			free(file_name);
 			return file;
 		}
 	}
@@ -104,7 +104,7 @@ void str_append(struct gstr *gs, const char *s)
 	if (s) {
 		l = strlen(gs->s) + strlen(s) + 1;
 		if (l > gs->len) {
-			gs->s   = realloc(gs->s, l);
+			gs->s = xrealloc(gs->s, l);
 			gs->len = l;
 		}
 		strcat(gs->s, s);
@@ -145,3 +145,23 @@ void *xcalloc(size_t nmemb, size_t size)
 	fprintf(stderr, "Out of memory.\n");
 	exit(1);
 }
+
+void *xrealloc(void *p, size_t size)
+{
+	p = realloc(p, size);
+	if (p)
+		return p;
+	fprintf(stderr, "Out of memory.\n");
+	exit(1);
+}
+
+char *xstrdup(const char *s)
+{
+	char *p;
+
+	p = strdup(s);
+	if (p)
+		return p;
+	fprintf(stderr, "Out of memory.\n");
+	exit(1);
+}
diff --git a/kconfig/zconf.l b/kconfig/zconf.l
index c410d25..88b650e 100644
--- a/kconfig/zconf.l
+++ b/kconfig/zconf.l
@@ -52,7 +52,7 @@ static void append_string(const char *str, int size)
 	if (new_size > text_asize) {
 		new_size += START_STRSIZE - 1;
 		new_size &= -START_STRSIZE;
-		text = realloc(text, new_size);
+		text = xrealloc(text, new_size);
 		text_asize = new_size;
 	}
 	memcpy(text + text_size, str, size);
@@ -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;
 	}
 	\\.?	{
@@ -178,13 +178,15 @@ 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);
 	}
 	\n	{
-		printf("%s:%d:warning: multi-line strings not supported\n", zconf_curname(), zconf_lineno());
+		fprintf(stderr,
+			"%s:%d:warning: multi-line strings not supported\n",
+			zconf_curname(), zconf_lineno());
 		current_file->lineno++;
 		BEGIN(INITIAL);
 		return T_EOL;
@@ -261,7 +263,7 @@ void zconf_starthelp(void)
 
 static void zconf_endhelp(void)
 {
-	zconflval.string = text;
+	yylval.string = text;
 	BEGIN(INITIAL);
 }
 
@@ -294,7 +296,7 @@ void zconf_initscan(const char *name)
 {
 	yyin = zconf_fopen(name);
 	if (!yyin) {
-		printf("can't find file %s\n", name);
+		fprintf(stderr, "can't find file %s\n", name);
 		exit(1);
 	}
 
@@ -315,8 +317,8 @@ void zconf_nextfile(const char *name)
 	current_buf->state = YY_CURRENT_BUFFER;
 	yyin = zconf_fopen(file->name);
 	if (!yyin) {
-		printf("%s:%d: can't open file \"%s\"\n",
-		    zconf_curname(), zconf_lineno(), file->name);
+		fprintf(stderr, "%s:%d: can't open file \"%s\"\n",
+			zconf_curname(), zconf_lineno(), file->name);
 		exit(1);
 	}
 	yy_switch_to_buffer(yy_create_buffer(yyin, YY_BUF_SIZE));
@@ -325,20 +327,17 @@ void zconf_nextfile(const char *name)
 
 	for (iter = current_file->parent; iter; iter = iter->parent ) {
 		if (!strcmp(current_file->name,iter->name) ) {
-			printf("%s:%d: recursive inclusion detected. "
-			       "Inclusion path:\n  current file : '%s'\n",
-			       zconf_curname(), zconf_lineno(),
-			       zconf_curname());
-			iter = current_file->parent;
-			while (iter && \
-			       strcmp(iter->name,current_file->name)) {
-				printf("  included from: '%s:%d'\n",
-				       iter->name, iter->lineno-1);
+			fprintf(stderr,
+				"%s:%d: recursive inclusion detected. "
+				"Inclusion path:\n  current file : '%s'\n",
+				zconf_curname(), zconf_lineno(),
+				zconf_curname());
+			iter = current_file;
+			do {
 				iter = iter->parent;
-			}
-			if (iter)
-				printf("  included from: '%s:%d'\n",
-				       iter->name, iter->lineno+1);
+				fprintf(stderr, "  included from: '%s:%d'\n",
+					iter->name, iter->lineno - 1);
+			} while (strcmp(iter->name, current_file->name));
 			exit(1);
 		}
 	}
diff --git a/kconfig/zconf.y b/kconfig/zconf.y
index 5edf50c..283ad36 100644
--- a/kconfig/zconf.y
+++ b/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, xstrdup("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);
-	sym->flags |= SYMBOL_OPTIONAL;
-	menu_add_entry(sym);
-	printd(DEBUG_PARSE, "%s:%d:config %s\n", zconf_curname(), zconf_lineno(), $2);
+	$2->flags |= SYMBOL_OPTIONAL;
+	menu_add_entry($2);
+	printd(DEBUG_PARSE, "%s:%d:config %s\n", zconf_curname(), zconf_lineno(), $2->name);
 };
 
 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);
-	sym->flags |= SYMBOL_OPTIONAL;
-	menu_add_entry(sym);
-	printd(DEBUG_PARSE, "%s:%d:menuconfig %s\n", zconf_curname(), zconf_lineno(), $2);
+	$2->flags |= SYMBOL_OPTIONAL;
+	menu_add_entry($2);
+	printd(DEBUG_PARSE, "%s:%d:menuconfig %s\n", zconf_curname(), zconf_lineno(), $2->name);
 };
 
 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);
@@ -257,6 +276,7 @@ choice: T_CHOICE word_opt T_EOL
 	sym->flags |= SYMBOL_AUTO;
 	menu_add_entry(sym);
 	menu_add_expr(P_CHOICE, NULL, NULL);
+	free($2);
 	printd(DEBUG_PARSE, "%s:%d:choice\n", zconf_curname(), zconf_lineno());
 };
 
@@ -308,10 +328,10 @@ 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 +371,6 @@ 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 +407,7 @@ 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 +420,7 @@ comment: T_COMMENT prompt T_EOL
 };
 
 comment_stmt: comment depends_list
-{
-	menu_end_entry();
-};
+;
 
 /* help option */
 
@@ -420,6 +432,17 @@ 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>");
+	}
+
+	/* Is the help text empty or all whitespace? */
+	if ($2[strspn($2, " \f\n\r\t\v")] == '\0')
+		zconfprint("warning: '%s' defined with blank help text",
+			   current_entry->sym->name ?: "<choice>");
+
 	current_entry->help = $2;
 };
 
@@ -491,7 +514,10 @@ 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 +528,7 @@ word_opt: /* empty */			{ $$ = NULL; }
 
 void conf_parse(const char *name)
 {
+	const char *tmp;
 	struct symbol *sym;
 	int i;
 
@@ -509,27 +536,28 @@ void conf_parse(const char *name)
 
 	sym_init();
 	_menu_init();
-	rootmenu.prompt = menu_add_prompt(P_MENU, "Crosstool-NG Configuration", NULL);
 
 #if YYDEBUG
 	if (getenv("ZCONF_DEBUG"))
-		zconfdebug = 1;
+		yydebug = 1;
 #endif
-	zconfparse();
-	if (zconfnerrs)
+	yyparse();
+	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);
 }
@@ -554,7 +582,7 @@ 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) {
@@ -563,7 +591,7 @@ 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;
@@ -584,7 +612,7 @@ 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);
@@ -592,7 +620,7 @@ 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);
 }
@@ -625,7 +653,7 @@ 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);