pull exit check out of State::execute

corewords.cpp

@@ -168,18 +168,22 @@ execute:
         break;
     case 25: // exit
         state.ip = state.popr();
+        if (state.ip == 0) {
+            std::longjmp(state.jmpbuf,
+                static_cast<int>(State::Error::exit));
+        }
         break;
     case 26: // semic
         state.dict.add(findi("exit"));
         state.compiling(false);
         break;
-    case 27: // _jmp
-        state.ip = state.beyondip() - sizeof(Cell);
-        break;
-    case 28: // _jmp0
-        if (state.pop())
+    case 27: // _jmp0
+        if (state.pop()) {
             state.beyondip();
-        else
+            break;
+        }
+        [[fallthrough]];
+    case 28: // _jmp
         state.ip = state.beyondip() - sizeof(Cell);
         break;
     case 29: // depth

corewords.hpp

@@ -44,8 +44,8 @@ private:
         "_@\0_!\0>r\0r>\0=\0"
         "<\0&\0|\0^\0"
         "<<\0>>\0:\0'\0execute\0"
-        "exit\0;\1_jmp\0"
-        "_jmp0\0depth\0_rdepth\0key\0";
+        "exit\0;\1_jmp0\0_jmp\0"
+        "depth\0_rdepth\0key\0";
 };
 
 #endif // ALEEFORTH_COREWORDS_HPP

state.cpp

@@ -35,20 +35,20 @@ State::Error State::execute(Addr addr)
 {
     auto stat = setjmp(jmpbuf);
     if (!stat) {
-        ip = 0;
-
+        if (addr < CoreWords::WordCount) {
+            CoreWords::run(addr, *this);
+        } else {
             auto ins = addr;
+
             for (;;) {
                 CoreWords::run(ins, *this);
-
-            if (!ip)
-                break;
-
                 ip += sizeof(Cell);
                 ins = dict.read(ip);
             }
+        }
     } else {
-        return static_cast<State::Error>(stat);
+        auto err = static_cast<State::Error>(stat);
+        return err == State::Error::exit ? State::Error::none : err;
     }
 
     return State::Error::none;

state.hpp

@@ -37,7 +37,8 @@ struct State
         pushr,
         popr,
         top,
-        pick
+        pick,
+        exit
     };
 
     Addr ip = 0;