Extend deferred warnings system with tentative defs.

Tentative defs record the fact that some definition has been
seen at expansion time, even though that definition has not
been put into effect. They suppress warnings.

* unwind.c (tentative_defs): New static variable.
(uw_defer_warning): Throw away the warning if
it matches a tentative def.
(uw_register_tentative_def, uw_tentative_def_exists): New
functions.
(uw_dump_deferred_warnings): Purge the tag from the list of
deferred defs also.
(uw_init): gc-protect tentative_defs.
Register intrinsics register-tentative-def and
tentative-def-exists.

* unwind.h (uw_register_tentative_def,
uw_tentative_def_exists): Declared.

1 files changed, 19 insertions, 3 deletions

diff --git a/unwind.c b/unwind.c
index 4f259e06..4d3b3902 100644
--- a/unwind.c
+++ b/unwind.c
@@ -59,7 +59,7 @@ static val sys_cont_free_s, sys_capture_cont_s;
 
 static val frame_type, catch_frame_type, handle_frame_type;
 
-static val deferred_warnings;
+static val deferred_warnings, tentative_defs;
 
 /* C99 inline instantiations. */
 #if __STDC_VERSION__ >= 199901L
@@ -676,10 +676,23 @@ val type_mismatch(val fmt, ...)
 
 val uw_defer_warning(val args)
 {
-  push(args, &deferred_warnings);
+  val tag = cdr(args);
+  if (!memqual(tag, tentative_defs))
+    push(args, &deferred_warnings);
   return nil;
 }
 
+val uw_register_tentative_def(val tag)
+{
+  push(tag, &tentative_defs);
+  return nil;
+}
+
+val uw_tentative_def_exists(val tag)
+{
+  return memqual(tag, tentative_defs);
+}
+
 val uw_dump_deferred_warnings(val stream)
 {
   val wl = nreverse(zap(&deferred_warnings));
@@ -695,6 +708,7 @@ val uw_dump_deferred_warnings(val stream)
 val uw_purge_deferred_warning(val tag)
 {
   deferred_warnings = remqual(tag, deferred_warnings, cdr_f);
+  tentative_defs = remqual(tag, tentative_defs, nil);
   return nil;
 }
 
@@ -998,7 +1012,7 @@ void uw_init(void)
 void uw_late_init(void)
 {
   protect(&frame_type, &catch_frame_type, &handle_frame_type,
-          &deferred_warnings, convert(val *, 0));
+          &deferred_warnings, &tentative_defs, convert(val *, 0));
   types_s = intern(lit("types"), user_package);
   jump_s = intern(lit("jump"), user_package);
   sys_cont_s = intern(lit("cont"), system_package);
@@ -1024,6 +1038,8 @@ void uw_late_init(void)
   reg_fun(error_s, func_n1v(uw_errorfv));
   reg_fun(intern(lit("purge-deferred-warning"), user_package),
           func_n1(uw_purge_deferred_warning));
+  reg_fun(intern(lit("register-tentative-def"), user_package), func_n1(uw_register_tentative_def));
+  reg_fun(intern(lit("tentative-def-exists"), user_package), func_n1(uw_tentative_def_exists));
   reg_fun(intern(lit("register-exception-subtypes"), user_package),
           func_n0v(register_exception_subtypes));
   reg_fun(intern(lit("exception-subtype-p"), user_package),