This is the first of two commits (didn't want to dump them all into the

same one). However, the first will temporarily break things until the
second comes through. :-)

The safestack.h handling was mapping compare callbacks that externally
are of the type (int (*)(type **,type **)) into the underlying callback
type used by stack.[ch], which is (int (*)(void *,void *)). After some
degree of digging, it appears that the callback type in the underlying
stack code should use double pointers too - when the compare operations
are invoked (from sk_find and sk_sort), they are being used by bsearch
and qsort to compare two pointers to pointers. This change corrects the
prototyping (by only casting to the (void*,void*) form at the moment
it is needed by bsearch and qsort) and makes the mapping in safestack.h
more transparent. It also changes from "void*" to "char*" to stay in
keeping with stack.[ch]'s assumed base type of "char".

Also - the "const" situation was that safestack.h was throwing away
"const"s, and to compound the problem - a close examination of stack.c
showed that (const char **) is not really achieving what it is supposed
to when the callback is being invoked, what is needed is
(const char * const *). So the underlying stack.[ch] and the mapping
macros in safestack.h have all been altered to correct this.

What will follow are the vast quantities of "const" corrections required
in stack-dependant code that was being let "slip" through when
safestack.h was discarding "const"s. These now all come up as compiler
warnings.

crypto/stack/safestack.h

@@ -65,7 +65,8 @@ STACK_OF(type) \
     { \
     STACK stack; \
     }; \
-STACK_OF(type) *sk_##type##_new(int (*cmp)(type **,type **)); \
+STACK_OF(type) *sk_##type##_new(int (*cmp)(const type * const *, \
+				const type * const *)); \
 STACK_OF(type) *sk_##type##_new_null(void); \
 void sk_##type##_free(STACK_OF(type) *sk); \
 int sk_##type##_num(const STACK_OF(type) *sk); \
@@ -76,10 +77,11 @@ int sk_##type##_push(STACK_OF(type) *sk,type *v); \
 int sk_##type##_unshift(STACK_OF(type) *sk,type *v); \
 int sk_##type##_find(STACK_OF(type) *sk,type *v); \
 type *sk_##type##_delete(STACK_OF(type) *sk,int n); \
-void sk_##type##_delete_ptr(STACK_OF(type) *sk,type *v); \
+type *sk_##type##_delete_ptr(STACK_OF(type) *sk,type *v); \
 int sk_##type##_insert(STACK_OF(type) *sk,type *v,int n); \
 int (*sk_##type##_set_cmp_func(STACK_OF(type) *sk, \
-			       int (*cmp)(type **,type **)))(type **,type **); \
+	int (*cmp)(const type * const *,const type * const *))) \
+	(const type * const *,const type * const *); \
 STACK_OF(type) *sk_##type##_dup(STACK_OF(type) *sk); \
 void sk_##type##_pop_free(STACK_OF(type) *sk,void (*func)(type *)); \
 type *sk_##type##_shift(STACK_OF(type) *sk); \
@@ -87,8 +89,10 @@ type *sk_##type##_pop(STACK_OF(type) *sk); \
 void sk_##type##_sort(STACK_OF(type) *sk);
 
 #define IMPLEMENT_STACK_OF(type) \
-STACK_OF(type) *sk_##type##_new(int (*cmp)(type **,type **)) \
-    { return (STACK_OF(type) *)sk_new((int (*)())cmp); } \
+STACK_OF(type) *sk_##type##_new(int (*cmp)(const type * const *, \
+				const type * const *)) \
+    { return (STACK_OF(type) *)sk_new( \
+        (int (*)(const char * const *,const char * const *))cmp); } \
 STACK_OF(type) *sk_##type##_new_null() \
     { return (STACK_OF(type) *)sk_new_null(); } \
 void sk_##type##_free(STACK_OF(type) *sk) \
@@ -109,13 +113,15 @@ int sk_##type##_find(STACK_OF(type) *sk,type *v) \
     { return sk_find((STACK *)sk,(char *)v); } \
 type *sk_##type##_delete(STACK_OF(type) *sk,int n) \
     { return (type *)sk_delete((STACK *)sk,n); } \
-void sk_##type##_delete_ptr(STACK_OF(type) *sk,type *v) \
-    { sk_delete_ptr((STACK *)sk,(char *)v); } \
+type *sk_##type##_delete_ptr(STACK_OF(type) *sk,type *v) \
+    { return (type *)sk_delete_ptr((STACK *)sk,(char *)v); } \
 int sk_##type##_insert(STACK_OF(type) *sk,type *v,int n) \
     { return sk_insert((STACK *)sk,(char *)v,n); } \
 int (*sk_##type##_set_cmp_func(STACK_OF(type) *sk, \
-			       int (*cmp)(type **,type **)))(type **,type **) \
-    { return (int (*)(type **,type **))sk_set_cmp_func((STACK *)sk,(int(*)(const void *, const void *))cmp); } \
+	int (*cmp)(const type * const *,const type * const *))) \
+	(const type * const *,const type * const *) \
+    { return (int (*)(const type * const *,const type * const *))sk_set_cmp_func( \
+	(STACK *)sk, (int(*)(const char * const *, const char * const *))cmp); } \
 STACK_OF(type) *sk_##type##_dup(STACK_OF(type) *sk) \
     { return (STACK_OF(type) *)sk_dup((STACK *)sk); } \
 void sk_##type##_pop_free(STACK_OF(type) *sk,void (*func)(type *)) \

crypto/stack/stack.c

@@ -76,9 +76,10 @@ const char *STACK_version="Stack" OPENSSL_VERSION_PTEXT;
 
 #include <errno.h>
 
-int (*sk_set_cmp_func(STACK *sk, int (*c)(const void *,const void *)))(const void *, const void *)
+int (*sk_set_cmp_func(STACK *sk, int (*c)(const char * const *,const char * const *)))
+		(const char * const *, const char * const *)
 	{
-	int (*old)(const void *,const void *)=sk->comp;
+	int (*old)(const char * const *,const char * const *)=sk->comp;
 
 	if (sk->comp != c)
 		sk->sorted=0;
@@ -108,7 +109,7 @@ err:
 	return(NULL);
 	}
 
-STACK *sk_new(int (*c)(const void *, const void *))
+STACK *sk_new(int (*c)(const char * const *, const char * const *))
 	{
 	STACK *ret;
 	int i;
@@ -218,13 +219,24 @@ int sk_find(STACK *st, char *data)
 		}
 	sk_sort(st);
 	if (data == NULL) return(-1);
-	comp_func=st->comp;
+	/* This (and the "qsort" below) are the two places in OpenSSL
+	 * where we need to convert from our standard (type **,type **)
+	 * compare callback type to the (void *,void *) type required by
+	 * bsearch. However, the "data" it is being called(back) with are
+	 * not (type *) pointers, but the *pointers* to (type *) pointers,
+	 * so we get our extra level of pointer dereferencing that way. */
+	comp_func=(int (*)(const void *,const void *))(st->comp);
 	r=(char **)bsearch(&data,(char *)st->data,
 		st->num,sizeof(char *), comp_func);
 	if (r == NULL) return(-1);
 	i=(int)(r-st->data);
 	for ( ; i>0; i--)
-		if ((*st->comp)(&(st->data[i-1]),&data) < 0)
+		/* This needs a cast because the type being pointed to from
+		 * the "&" expressions are (char *) rather than (const char *).
+		 * For an explanation, read:
+		 * http://www.eskimo.com/~scs/C-faq/q11.10.html :-) */
+		if ((*st->comp)((const char * const *)&(st->data[i-1]),
+				(const char * const *)&data) < 0)
 			break;
 	return(i);
 	}
@@ -303,7 +315,12 @@ void sk_sort(STACK *st)
 	{
 	int (*comp_func)(const void *,const void *);
 
-	comp_func=st->comp;
+	/* same comment as in sk_find ... previously st->comp was declared
+	 * as a (void*,void*) callback type, but this made the population
+	 * of the callback pointer illogical - our callbacks compare
+	 * type** with type**, so we leave the casting until absolutely
+	 * necessary (ie. "now"). */
+	comp_func=(int (*)(const void *,const void *))(st->comp);
 	qsort(st->data,st->num,sizeof(char *), comp_func);
 	st->sorted=1;
 	}

crypto/stack/stack.h

@@ -70,11 +70,11 @@ typedef struct stack_st
 	int sorted;
 
 	int num_alloc;
-	int (*comp)(const void *, const void *);
+	int (*comp)(const char * const *, const char * const *);
 	} STACK;
 
-
-#define sk_new_null()	sk_new(NULL)
+#define sk_new_null()	sk_new((int (*)(const char * const *, \
+				const char * const *))NULL)
 
 #define M_sk_num(sk)		((sk) ? (sk)->num:-1)
 #define M_sk_value(sk,n)	((sk) ? (sk)->data[n] : NULL)
@@ -84,7 +84,7 @@ char *sk_value(const STACK *, int);
 
 char *sk_set(STACK *, int, char *);
 
-STACK *sk_new(int (*cmp)(const void *, const void *));
+STACK *sk_new(int (*cmp)(const char * const *, const char * const *));
 void sk_free(STACK *);
 void sk_pop_free(STACK *st, void (*func)(void *));
 int sk_insert(STACK *sk,char *data,int where);
@@ -96,7 +96,9 @@ int sk_unshift(STACK *st,char *data);
 char *sk_shift(STACK *st);
 char *sk_pop(STACK *st);
 void sk_zero(STACK *st);
-int (*sk_set_cmp_func(STACK *sk, int (*c)(const void *,const void *)))(const void *, const void *);
+int (*sk_set_cmp_func(STACK *sk, int (*c)(const char * const *,
+			const char * const *)))
+			(const char * const *, const char * const *);
 STACK *sk_dup(STACK *st);
 void sk_sort(STACK *st);