Implement two stack growth policies.

* mfd/gram.y (pragma_stacksize): Implement two stack growth
policies.
* mfd/mailfromd.h (enum stack_expand_policy): New enum.
(stack_expand_incr, stack_expand_policy): New global variables.
* mfd/prog.c (stack_expand_incr)
(stack_expand_policy): New global variables.

* NEWS: Update.
* doc/mailfromd.texi (stacksize): Document changes to pragma
stacksize. 
* doc/values.texi (STACK-INCR): New value.


git-svn-id: file:///svnroot/mailfromd/trunk@1676 7a8a7f39-df28-0410-adc6-e0d955640f24

1 files changed, 35 insertions, 11 deletions

diff --git a/mfd/prog.c b/mfd/prog.c
index 4a363072..25f9f220 100644
--- a/mfd/prog.c
+++ b/mfd/prog.c
@@ -46,6 +46,8 @@
 static prog_counter_t pc, pmax;
 instr_t *prog;
 size_t stack_size = 4096;
+size_t stack_expand_incr = 4096;
+enum stack_expand_policy stack_expand_policy = stack_expand_add;
 
 /* Data segment */
 STKVAL *dataseg;
@@ -384,32 +386,54 @@ env_fixup_autos(eval_environ_t env, ptrdiff_t offset)
 }
 
 
-#define STACK_EXPAND_BLOCK 64
-
 static int
 expand_dataseg(eval_environ_t env, size_t count, const char *errtext)
 {
 	STKVAL *newds;
 	ptrdiff_t offset;
+	size_t new_stack_size;
+	size_t diff;
+	
+	switch (stack_expand_policy) {
+	case stack_expand_add:
+		diff = ((count + stack_expand_incr - 1) / stack_expand_incr)
+			* stack_expand_incr;
+		new_stack_size = env->stack_size + diff;
+		break;
+
+	case stack_expand_twice:
+		new_stack_size = 2 * env->stack_size;
+		if (new_stack_size < env->stack_size) {
+			if (errtext)
+				runtime_error(env, errtext);
+			else
+				return 1;
+		}
+		diff = new_stack_size - env->stack_size;
+		if (diff < count) {
+			if (errtext)
+				runtime_error(env, errtext);
+			else
+				return 1;
+		}
+	}
 	
-	count = ((count + STACK_EXPAND_BLOCK - 1) / STACK_EXPAND_BLOCK)
-		* STACK_EXPAND_BLOCK;
 	newds = realloc(env->dataseg,
-			(env->stack_size + datasize + count)
-			  * sizeof env->dataseg[0]);
+			(new_stack_size + datasize) * sizeof env->dataseg[0]);
+		
 	if (!newds) {
 		if (errtext)
 			runtime_error(env, errtext);
 		else
 			return 1;
 	}
-
+	
 	offset = (char*)newds - (char*)env->dataseg;
 	env->dataseg = newds;
-	env->stack_size += count;
-	env->tos += count;
-	env->base += count;
-	memmove(newds + env->tos, newds + env->tos - count,
+	env->stack_size = new_stack_size;
+	env->tos += diff;
+	env->base += diff;
+	memmove(newds + env->tos, newds + env->tos - diff,
 		(datasize + env->stack_size - env->tos)
  		  * sizeof newds[0]);
 	env_fixup_autos(env, offset);