Fix start-context-and-delete sub-primitive (reported by Sascha Matzke)

basis/cpu/x86/32/bootstrap.factor

@@ -335,7 +335,18 @@ IN: bootstrap.x86
     jit-set-context
 ] \ (set-context-and-delete) define-sub-primitive
 
+: jit-start-context-and-delete ( -- )
+    jit-load-vm
+    jit-load-context
+    ESP [] vm-reg MOV
+    ESP 4 [+] ctx-reg MOV
+    "reset_context" jit-call
+
+    jit-pop-quot-and-param
+    ctx-reg jit-switch-context
+    jit-push-param
+    jit-jump-quot ;
+
 [
-    jit-delete-current-context
-    jit-start-context
+    jit-start-context-and-delete
 ] \ (start-context-and-delete) define-sub-primitive

basis/cpu/x86/64/bootstrap.factor

@@ -230,9 +230,6 @@ IN: bootstrap.x86
 : jit-switch-context ( reg -- )
     -8 jit-scrub-return
 
-    ! Save ds, rs registers
-    jit-save-context
-
     ! Make the new context the current one
     ctx-reg swap MOV
     vm-reg vm-context-offset [+] ctx-reg MOV
@@ -257,6 +254,7 @@ IN: bootstrap.x86
 
 : jit-set-context ( -- )
     jit-pop-context-and-param
+    jit-save-context
     arg1 jit-switch-context
     RSP 8 ADD
     jit-push-param ;
@@ -269,17 +267,17 @@ IN: bootstrap.x86
     ds-reg 16 SUB ;
 
 : jit-start-context ( -- )
-    ! Create the new context in return-reg
+    ! Create the new context in return-reg. Have to save context
+    ! twice, first before calling new_context() which may GC,
+    ! and again after popping the two parameters from the stack.
     jit-save-context
     arg1 vm-reg MOV
     "new_context" jit-call
 
     jit-pop-quot-and-param
-
+    jit-save-context
     return-reg jit-switch-context
-
     jit-push-param
-
     jit-jump-quot ;
 
 [ jit-start-context ] \ (start-context) define-sub-primitive
@@ -295,7 +293,17 @@ IN: bootstrap.x86
     jit-set-context
 ] \ (set-context-and-delete) define-sub-primitive
 
+: jit-start-context-and-delete ( -- )
+    jit-load-context
+    arg1 vm-reg MOV
+    arg2 ctx-reg MOV
+    "reset_context" jit-call
+
+    jit-pop-quot-and-param
+    ctx-reg jit-switch-context
+    jit-push-param
+    jit-jump-quot ;
+
 [
-    jit-delete-current-context
-    jit-start-context
+    jit-start-context-and-delete
 ] \ (start-context-and-delete) define-sub-primitive

vm/contexts.cpp

@@ -166,6 +166,12 @@ VM_C_API void delete_context(factor_vm *parent, context *old_context)
 	parent->delete_context(old_context);
 }
 
+VM_C_API void reset_context(factor_vm *parent, context *ctx)
+{
+	ctx->reset();
+	parent->init_context(ctx);
+}
+
 cell factor_vm::begin_callback(cell quot_)
 {
 	data_root<object> quot(quot_,this);

vm/contexts.hpp

@@ -73,6 +73,7 @@ struct context {
 
 VM_C_API context *new_context(factor_vm *parent);
 VM_C_API void delete_context(factor_vm *parent, context *old_context);
+VM_C_API void reset_context(factor_vm *parent, context *ctx);
 VM_C_API cell begin_callback(factor_vm *parent, cell quot);
 VM_C_API void end_callback(factor_vm *parent);