Add support for debugging upvalues.

Upvalues are stored in the symbol slots structure as well, but
since they are always live, we repurpose the death_pc field to
refer to the environment index that we want to look at at runtime.

src/boot/boot.janet

@@ -2767,12 +2767,6 @@
   (put nextenv :debug-level level)
   (put nextenv :signal (fiber/last-value fiber))
 
-  # define variables available at breakpoint
-  (def frame ((debug/stack fiber) 0))
-  (def pc (frame :pc))
-  (eachp [local value] (get frame :locals)
-    (put nextenv local @{:value value}))
-
   (merge-into nextenv debugger-env)
   (defn debugger-chunks [buf p]
     (def status (:state p :delimiters))
@@ -3381,11 +3375,16 @@
   (print))
 
 (defn .frame
-  "Show a stack frame."
+  "Show a stack frame"
   [&opt n]
   (def stack (debug/stack (.fiber)))
   (in stack (or n 0)))
 
+(defn .locals
+  "Show local bindings"
+  [&opt n]
+  (get (.frame n) :locals))
+
 (defn .fn
   "Get the current function."
   [&opt n]

src/core/asm.c

@@ -928,10 +928,15 @@ static Janet janet_disasm_symbolslots(JanetFuncDef *def) {
         return janet_wrap_nil();
     }
     JanetArray *symbolslots = janet_array(def->symbolmap_length);
+    Janet upvaluekw = janet_ckeywordv("upvalue");
     for (int32_t i = 0; i < def->symbolmap_length; i++) {
         JanetSymbolMap ss = def->symbolmap[i];
         Janet *t = janet_tuple_begin(4);
-        t[0] = janet_wrap_integer(ss.birth_pc);
+        if (ss.birth_pc == UINT32_MAX) {
+            t[0] = upvaluekw;
+        } else {
+            t[0] = janet_wrap_integer(ss.birth_pc);
+        }
         t[1] = janet_wrap_integer(ss.death_pc);
         t[2] = janet_wrap_integer(ss.slot_index);
         t[3] = janet_wrap_symbol(ss.symbol);

src/core/compile.c

@@ -344,6 +344,7 @@ found:
     }
 
     /* non-local scope needs to expose its environment */
+    JanetScope *original_scope = scope;
     pair->keep = 1;
     while (scope && !(scope->flags & JANET_SCOPE_FUNCTION))
         scope = scope->parent;
@@ -365,7 +366,7 @@ found:
             /* Check if scope already has env. If so, break */
             len = janet_v_count(scope->envs);
             for (j = 0; j < len; j++) {
-                if (scope->envs[j] == envindex) {
+                if (scope->envs[j].envindex == envindex) {
                     scopefound = 1;
                     envindex = j;
                     break;
@@ -374,7 +375,10 @@ found:
             /* Add the environment if it is not already referenced */
             if (!scopefound) {
                 len = janet_v_count(scope->envs);
-                janet_v_push(scope->envs, envindex);
+                JanetEnvRef ref;
+                ref.envindex = envindex;
+                ref.scope = original_scope;
+                janet_v_push(scope->envs, ref);
                 envindex = len;
             }
         }
@@ -878,7 +882,10 @@ JanetFuncDef *janetc_pop_funcdef(JanetCompiler *c) {
 
     /* Copy envs */
     def->environments_length = janet_v_count(scope->envs);
-    def->environments = janet_v_flatten(scope->envs);
+    def->environments = janet_malloc(sizeof(int32_t) * def->environments_length);
+    for (int32_t i = 0; i < def->environments_length; i++) {
+        def->environments[i] = scope->envs[i].envindex;
+    }
 
     def->constants_length = janet_v_count(scope->consts);
     def->constants = janet_v_flatten(scope->consts);
@@ -935,6 +942,30 @@ JanetFuncDef *janetc_pop_funcdef(JanetCompiler *c) {
 
     /* Capture symbol to local mapping */
     JanetSymbolMap *locals = NULL;
+
+    /* Symbol -> upvalue mapping */
+    JanetScope *top = c->scope;
+    while (top->parent) top = top->parent;
+    for (JanetScope *s = top; s != NULL; s = s->child) {
+        for (int32_t j = 0; j < janet_v_count(scope->envs); j++) {
+            JanetEnvRef ref = scope->envs[j];
+            JanetScope *upscope = ref.scope;
+            if (upscope != s) continue;
+            for (int32_t i = 0; i < janet_v_count(upscope->syms); i++) {
+                SymPair pair = upscope->syms[i];
+                if (pair.sym2) {
+                    JanetSymbolMap jsm;
+                    jsm.birth_pc = UINT32_MAX;
+                    jsm.death_pc = j;
+                    jsm.slot_index = pair.slot.index;
+                    jsm.symbol = pair.sym2;
+                    janet_v_push(locals, jsm);
+                }
+            }
+        }
+    }
+
+    /* Symbol -> slot mapping */
     for (int32_t i = 0; i < janet_v_count(scope->syms); i++) {
         SymPair pair = scope->syms[i];
         if (pair.sym2) {

src/core/compile.h

@@ -117,6 +117,11 @@ typedef struct SymPair {
     uint32_t death_pc;
 } SymPair;
 
+typedef struct JanetEnvRef {
+    int32_t envindex;
+    JanetScope *scope;
+} JanetEnvRef;
+
 /* A lexical scope during compilation */
 struct JanetScope {
 
@@ -145,7 +150,7 @@ struct JanetScope {
     /* Referenced closure environments. The values at each index correspond
      * to which index to get the environment from in the parent. The environment
      * that corresponds to the direct parent's stack will always have value 0. */
-    int32_t *envs;
+    JanetEnvRef *envs;
 
     int32_t bytecode_start;
     int flags;

src/core/debug.c

@@ -334,10 +334,19 @@ static Janet doframe(JanetStackFrame *frame) {
             JanetTable *local_bindings = janet_table(0);
             for (int32_t i = def->symbolmap_length - 1; i >= 0; i--) {
                 JanetSymbolMap jsm = def->symbolmap[i];
+                Janet value = janet_wrap_nil();
                 uint32_t pc = (uint32_t)(frame->pc - def->bytecode);
-                if (pc >= jsm.birth_pc && pc < jsm.death_pc) {
+                if (jsm.birth_pc == UINT32_MAX) {
-                    janet_table_put(local_bindings, janet_wrap_symbol(jsm.symbol), stack[jsm.slot_index]);
+                    JanetFuncEnv *env = frame->func->envs[jsm.death_pc];
+                    if (env->offset > 0) {
+                        value = env->as.fiber->data[env->offset + jsm.slot_index];
+                    } else {
+                        value = env->as.values[jsm.slot_index];
+                    }
+                } else if (pc >= jsm.birth_pc && pc < jsm.death_pc) {
+                    value = stack[jsm.slot_index];
                 }
+                janet_table_put(local_bindings, janet_wrap_symbol(jsm.symbol), value);
             }
             janet_table_put(t, janet_ckeywordv("locals"), janet_wrap_table(local_bindings));
         }