4 files changed, 26 insertions, 6 deletions

diff --git a/ChangeLog b/ChangeLog
index 50671b4b..a5be43ec 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,24 @@
 2014-02-28  Kaz Kylheku  <kaz@kylheku.com>
 
+	Turn *gensym-counter* into proper special variable.
+
+	* eval.c (eval_init): Save *gensym-counter* symbol in gensym_counter_s
+	symbol variable right after interning, and use zero as the inital value
+	rather than the gensym_counter variable which is removed now.
+
+	* lib.c (gensym_counter_s): New symbol variable.
+	(gensym_counter): Variable removed.
+	(gensym): Slight refactoring to avoid a double variable lookup.
+	Also, for generational GC correctness, use the set macro to update it,
+	since the variable could live inside heap object and the counter
+	could overflow to bignums which are heap objects.
+	(obj_init): Remove initialization of gensym_counter.
+
+	* lib.h (gensym_counter_s): Declared.
+	(gensym_counter): Declaration removed, replaced by macro.
+
+2014-02-28  Kaz Kylheku  <kaz@kylheku.com>
+
 	Change in the design of how special variables work, to fix the broken
 	re-binding. C code now has to go through the dynamic environment lookup
 	to access things like *random-state*, or *stdout*.  As part of this,
diff --git a/eval.c b/eval.c
index ec074b05..89b9c5b5 100644
--- a/eval.c
+++ b/eval.c
@@ -3294,7 +3294,7 @@ void eval_init(void)
 
   reg_fun(intern(lit("make-sym"), user_package), func_n1(make_sym));
   reg_fun(intern(lit("gensym"), user_package), func_n1o(gensym, 0));
-  reg_var(intern(lit("*gensym-counter*"), user_package), gensym_counter);
+  reg_var(gensym_counter_s = intern(lit("*gensym-counter*"), user_package), zero);
   reg_fun(intern(lit("make-package"), user_package), func_n1(make_package));
   reg_fun(intern(lit("find-package"), user_package), func_n1(find_package));
   reg_fun(intern(lit("delete-package"), user_package), func_n1(delete_package));
diff --git a/lib.c b/lib.c
index c615b05b..dee6af8f 100644
--- a/lib.c
+++ b/lib.c
@@ -86,6 +86,7 @@ val eof_s, eol_s;
 val error_s, type_error_s, internal_error_s;
 val numeric_error_s, range_error_s;
 val query_error_s, file_error_s, process_error_s;
+val gensym_counter_s;
 
 val nothrow_k, args_k, colon_k, auto_k;
 
@@ -95,8 +96,6 @@ val null_list;
 
 val identity_f, equal_f, eql_f, eq_f, car_f, cdr_f, null_f;
 
-val gensym_counter;
-
 val prog_string;
 
 static val env_list;
@@ -2704,8 +2703,9 @@ val make_sym(val name)
 val gensym(val prefix)
 {
   prefix = default_arg(prefix, lit("g"));
+  val *gs_loc = &gensym_counter;
   val name = format(nil, lit("~a~,04a"), prefix,
-                    gensym_counter = plus(gensym_counter, one), nao);
+                    set(*gs_loc, plus(*gs_loc, one)), nao);
   return make_sym(name);
 }
 
@@ -5213,7 +5213,6 @@ static void obj_init(void)
   car_f = func_n1(car);
   cdr_f = func_n1(cdr);
   null_f = func_n1(null);
-  gensym_counter = zero;
   prog_string = string(progname);
 }
 
diff --git a/lib.h b/lib.h
index cf6b02e0..b6eb69cc 100644
--- a/lib.h
+++ b/lib.h
@@ -340,6 +340,9 @@ extern val eof_s, eol_s;
 extern val error_s, type_error_s, internal_error_s;
 extern val numeric_error_s, range_error_s;
 extern val query_error_s, file_error_s, process_error_s;
+extern val gensym_counter_s;
+
+#define gensym_counter (*lookup_var_l(nil, gensym_counter_s))
 
 extern val nothrow_k, args_k, colon_k, auto_k;
 
@@ -348,7 +351,6 @@ extern val null_list; /* (nil) */
 
 extern val identity_f, equal_f, eql_f, eq_f, car_f, cdr_f, null_f;
 
-extern val gensym_counter;
 
 extern const wchar_t *progname;
 extern val prog_string;