From 38c955599f7c6c20faeec57d8e1df7d2c0eeba18 Mon Sep 17 00:00:00 2001
From: Justus Winter <justus@g10code.com>
Date: Thu, 16 Mar 2017 16:58:00 +0100
Subject: [PATCH] gpgscm: Remove framework for immediate values.

* tests/gpgscm/scheme.c (IMMEDIATE_TAG): Remove macro.
(is_immediate): Likewise.
(set_immediate): Likewise.
(clr_immediate): Likewise.
(enum scheme_types): Set the LSB in every value.
(fill_vector): Adapt.
(vector_elem): Likewise.
(set_vector_elem): Likewise.
(mark): Likewise.
(gc): Test for the LSB to tell typeflags apart from pointers stored in
the same memory location.
--

Supporting immediate values would require invasive changes to the
interpreter and is likely not worth the trouble.  On the other hand,
tagging pointers in vectors complicated the hash table implementation
needlessly.  Therefore, I remove this again.

This fixes a crash on big endian architectures.

GnuPG-bug-id: 2996
Signed-off-by: Justus Winter <justus@g10code.com>
---
 tests/gpgscm/scheme.c | 69 ++++++++++++++++++-------------------------
 1 file changed, 29 insertions(+), 40 deletions(-)

diff --git a/tests/gpgscm/scheme.c b/tests/gpgscm/scheme.c
index af97c27d6..ff91fc03f 100644
--- a/tests/gpgscm/scheme.c
+++ b/tests/gpgscm/scheme.c
@@ -117,41 +117,29 @@ static const char *strlwr(char *s) {
 
 
 
-/* Support for immediate values.
- *
- * Immediate values are tagged with IMMEDIATE_TAG, which is neither
- * used in types, nor in pointer values.
- *
- * XXX: Currently, we only use this to tag pointers in vectors.  */
-#define IMMEDIATE_TAG		1
-#define is_immediate(p)		((pointer) ((uintptr_t) (p) &  IMMEDIATE_TAG))
-#define set_immediate(p)	((pointer) ((uintptr_t) (p) |  IMMEDIATE_TAG))
-#define clr_immediate(p)	((pointer) ((uintptr_t) (p) & ~IMMEDIATE_TAG))
-
-
-
+/* All types have the LSB set.  The garbage collector takes advantage
+ * of that to identify types.  */
 enum scheme_types {
-  T_STRING=1 << 1,	/* Do not use the lsb, it is used for
-			 * immediate values.  */
-  T_NUMBER=2 << 1,
-  T_SYMBOL=3 << 1,
-  T_PROC=4 << 1,
-  T_PAIR=5 << 1,
-  T_CLOSURE=6 << 1,
-  T_CONTINUATION=7 << 1,
-  T_FOREIGN=8 << 1,
-  T_CHARACTER=9 << 1,
-  T_PORT=10 << 1,
-  T_VECTOR=11 << 1,
-  T_MACRO=12 << 1,
-  T_PROMISE=13 << 1,
-  T_ENVIRONMENT=14 << 1,
-  T_FOREIGN_OBJECT=15 << 1,
-  T_BOOLEAN=16 << 1,
-  T_NIL=17 << 1,
-  T_EOF_OBJ=18 << 1,
-  T_SINK=19 << 1,
-  T_LAST_SYSTEM_TYPE=19 << 1
+  T_STRING =		 1 << 1 | 1,
+  T_NUMBER =		 2 << 1 | 1,
+  T_SYMBOL =		 3 << 1 | 1,
+  T_PROC =		 4 << 1 | 1,
+  T_PAIR =		 5 << 1 | 1,
+  T_CLOSURE =		 6 << 1 | 1,
+  T_CONTINUATION =	 7 << 1 | 1,
+  T_FOREIGN =		 8 << 1 | 1,
+  T_CHARACTER =		 9 << 1 | 1,
+  T_PORT =		10 << 1 | 1,
+  T_VECTOR =		11 << 1 | 1,
+  T_MACRO =		12 << 1 | 1,
+  T_PROMISE =		13 << 1 | 1,
+  T_ENVIRONMENT =	14 << 1 | 1,
+  T_FOREIGN_OBJECT =	15 << 1 | 1,
+  T_BOOLEAN =		16 << 1 | 1,
+  T_NIL =		17 << 1 | 1,
+  T_EOF_OBJ =		18 << 1 | 1,
+  T_SINK =		19 << 1 | 1,
+  T_LAST_SYSTEM_TYPE =	19 << 1 | 1
 };
 
 static const char *
@@ -1361,20 +1349,20 @@ INTERFACE static void fill_vector(pointer vec, pointer obj) {
      size_t i;
      assert (is_vector (vec));
      for(i = 0; i < vector_length(vec); i++) {
-          vec->_object._vector._elements[i] = set_immediate(obj);
+          vec->_object._vector._elements[i] = obj;
      }
 }
 
 INTERFACE static pointer vector_elem(pointer vec, int ielem) {
      assert (is_vector (vec));
      assert (ielem < vector_length(vec));
-     return clr_immediate(vec->_object._vector._elements[ielem]);
+     return vec->_object._vector._elements[ielem];
 }
 
 INTERFACE static pointer set_vector_elem(pointer vec, int ielem, pointer a) {
      assert (is_vector (vec));
      assert (ielem < vector_length(vec));
-     vec->_object._vector._elements[ielem] = set_immediate(a);
+     vec->_object._vector._elements[ielem] = a;
      return a;
 }
 
@@ -1576,7 +1564,7 @@ E2:  setmark(p);
      if(is_vector(p)) {
           int i;
           for (i = 0; i < vector_length(p); i++) {
-               mark(clr_immediate(p->_object._vector._elements[i]));
+               mark(p->_object._vector._elements[i]);
           }
      }
 #if SHOW_ERROR_LINE
@@ -1677,8 +1665,9 @@ static void gc(scheme *sc, pointer a, pointer b) {
   for (i = sc->last_cell_seg; i >= 0; i--) {
     p = sc->cell_seg[i] + CELL_SEGSIZE;
     while (--p >= sc->cell_seg[i]) {
-      if (typeflag(p) & IMMEDIATE_TAG)
-        continue;
+      if ((typeflag(p) & 1) == 0)
+	/* All types have the LSB set.  This is not a typeflag.  */
+	continue;
       if (is_mark(p)) {
     clrmark(p);
       } else {