Miscellaneous code readability improvements.

* src/reader.c (reader): Move %define front-end variable
defaults and checking into...
(prepare_percent_define_front_end_variables): ... this new
function.

* src/scan-gram.l (INITIAL): For consistency with string
literals, don't store open quote on character literal.  It's
discarded before returning anyway.
(SC_ESCAPED_CHARACTER): Similarly, don't store close quote.
Make length test more readable, and make the character stored
for an empty literal more obvious while consistent with the
previous behavior.

* src/symtab.c, src/symtab.h: Rename USER_NUMBER_ALIAS to
USER_NUMBER_HAS_STRING_ALIAS throughout.
* src/symtab.c (symbol_make_alias): Remove comment from symtab.c
that is repeated in symtab.h.  Improve argument names to make it
clear which side of the symbol-string alias pair is which.
(symbol_check_alias_consistency): Improve local variable names
for the same purpose.
* src/symtab.h (struct symbol): Make comments about aliases
clearer.
(symbol_make_alias): Improve comments and argument name.
* src/output.c (token_definitions_output): Update for rename to
USER_NUMBER_HAS_STRING_ALIAS and improve comments about aliases.
(cherry picked from commit dfaa48602d4e6d329e3ae9063f44929490928b3d)

Conflicts:

	src/symtab.c
	src/symtab.h

1 files changed, 12 insertions, 9 deletions

diff --git a/src/symtab.h b/src/symtab.h
index b12c421a..882da710 100644
--- a/src/symtab.h
+++ b/src/symtab.h
@@ -85,9 +85,9 @@ struct symbol
   assoc assoc;
   int user_token_number;
 
-  /* Points to the other in the identifier-symbol pair for an alias.
-     Special value USER_NUMBER_ALIAS in the identifier half of the
-     identifier-symbol pair for an alias.  */
+  /* Points to the other in the symbol-string pair for an alias.
+     Special value USER_NUMBER_HAS_STRING_ALIAS in the symbol half of the
+     symbol-string pair for an alias.  */
   symbol *alias;
   symbol_class class;
   bool declared;
@@ -96,11 +96,11 @@ struct symbol
 /** Undefined user number.  */
 #define USER_NUMBER_UNDEFINED -1
 
-/* `symbol->user_token_number == USER_NUMBER_ALIAS' means this symbol
-   *has* (not is) a string literal alias.  For instance, `%token foo
+/* `symbol->user_token_number == USER_NUMBER_HAS_STRING_ALIAS' means
+   this symbol has a literal string alias.  For instance, `%token foo
    "foo"' has `"foo"' numbered regularly, and `foo' numbered as
-   USER_NUMBER_ALIAS.  */
-#define USER_NUMBER_ALIAS -9991
+   USER_NUMBER_HAS_STRING_ALIAS.  */
+#define USER_NUMBER_HAS_STRING_ALIAS -9991
 
 /* Undefined internal token number.  */
 #define NUMBER_UNDEFINED (-1)
@@ -122,8 +122,11 @@ symbol *dummy_symbol_get (location loc);
 /** Is this a dummy nonterminal?  */
 bool symbol_is_dummy (const symbol *sym);
 
-/** Declare the new symbol \c sym.  Make it an alias of \c symval.  */
-void symbol_make_alias (symbol *sym, symbol *symval, location loc);
+/**
+ * Make \c str the literal string alias of \c sym.  Copy token number,
+ * symbol number, and type from \c sym to \c str.
+ */
+void symbol_make_alias (symbol *sym, symbol *str, location loc);
 
 /** Set the \c type_name associated with \c sym.