https://github.com/akkartik/mu/blob/master/045closure_name.cc

      1 //: Writing to a literal (not computed) address of 0 in a recipe chains two
      2 //: spaces together. When a variable has a property of /space:1, it looks up
      3 //: the variable in the chained/surrounding space. /space:2 looks up the
      4 //: surrounding space of the surrounding space, etc.
      5 //:
      6 //: todo: warn on default-space abuse. default-space for one recipe should
      7 //: never come from another, otherwise memory will be corrupted.
      8
      9 :(scenario closure)
     10 def main [
     11   default-space:space <- new location:type, 30
     12   2:space/names:new-counter <- new-counter
     13   10:num/raw <- increment-counter 2:space/names:new-counter
     14   11:num/raw <- increment-counter 2:space/names:new-counter
     15 ]
     16 def new-counter [
     17   default-space:space <- new location:type, 30
     18   x:num <- copy 23
     19   y:num <- copy 13  # variable that will be incremented
     20   return default-space:space
     21 ]
     22 def increment-counter [
     23   default-space:space <- new location:type, 30
     24   0:space/names:new-counter <- next-ingredient  # outer space must be created by 'new-counter' above
     25   y:num/space:1 <- add y:num/space:1, 1  # increment
     26   y:num <- copy 234  # dummy
     27   return y:num/space:1
     28 ]
     29 +name: lexically surrounding space for recipe increment-counter comes from new-counter
     30 +mem: storing 15 in location 11
     31
     32 //: To make this work, compute the recipe that provides names for the
     33 //: surrounding space of each recipe.
     34
     35 :(before "End Globals")
     36 map<recipe_ordinal, recipe_ordinal> Surrounding_space;  // internal to transform; no need to snapshot
     37 :(before "End Reset")
     38 Surrounding_space.clear();
     39
     40 :(before "Begin Type Modifying Transforms")
     41 Transform.push_back(collect_surrounding_spaces);  // idempotent
     42
     43 :(code)
     44 void collect_surrounding_spaces(const recipe_ordinal r) {
     45   trace(9991, "transform") << "--- collect surrounding spaces for recipe " << get(Recipe, r).name << end();
     46   for (int i = 0;  i < SIZE(get(Recipe, r).steps);  ++i) {
     47     const instruction& inst = get(Recipe, r).steps.at(i);
     48     if (inst.is_label) continue;
     49     for (int j = 0;  j < SIZE(inst.products);  ++j) {
     50       if (is_literal(inst.products.at(j))) continue;
     51       if (inst.products.at(j).name != "0") continue;
     52       if (!is_mu_space(inst.products.at(j))) {
     53         raise << "slot 0 should always have type address:array:location, but is '" << to_string(inst.products.at(j)) << "'\n" << end();
     54         continue;
     55       }
     56       string_tree* s = property(inst.products.at(j), "names");
     57       if (!s) {
     58         raise << "slot 0 requires a /names property in recipe '" << get(Recipe, r).name << "'\n" << end();
     59         continue;
     60       }
     61       if (!s->atom) raise << "slot 0 should have a single value in /names, but got '" << to_string(inst.products.at(j)) << "'\n" << end();
     62       const string& surrounding_recipe_name = s->value;
     63       if (surrounding_recipe_name.empty()) {
     64         raise << "slot 0 doesn't initialize its /names property in recipe '" << get(Recipe, r).name << "'\n" << end();
     65         continue;
     66       }
     67       if (contains_key(Surrounding_space, r)
     68           && get(Surrounding_space, r) != get(Recipe_ordinal, surrounding_recipe_name)) {
     69         raise << "recipe '" << get(Recipe, r).name << "' can have only one 'surrounding' recipe but has '" << get(Recipe, get(Surrounding_space, r)).name << "' and '" << surrounding_recipe_name << "'\n" << end();
     70         continue;
     71       }
     72       trace(9993, "name") << "lexically surrounding space for recipe " << get(Recipe, r).name << " comes from " << surrounding_recipe_name << end();
     73       if (!contains_key(Recipe_ordinal, surrounding_recipe_name)) {
     74         raise << "can't find recipe providing surrounding space for '" << get(Recipe, r).name << "'; looking for '" << surrounding_recipe_name << "'\n" << end();
     75         continue;
     76       }
     77       put(Surrounding_space, r, get(Recipe_ordinal, surrounding_recipe_name));
     78     }
     79   }
     80 }
     81
     82 //: Once surrounding spaces are available, transform_names uses them to handle
     83 //: /space properties.
     84
     85 :(replace{} "int lookup_name(const reagent& r, const recipe_ordinal default_recipe)")
     86 int lookup_name(const reagent& x, const recipe_ordinal default_recipe) {
     87   if (!has_property(x, "space")) {
     88     if (Name[default_recipe].empty()) raise << "name not found: " << x.name << '\n' << end();
     89     return Name[default_recipe][x.name];
     90   }
     91   string_tree* p = property(x, "space");
     92   if (!p || !p->atom) raise << "/space property should have exactly one (non-negative integer) value\n" << end();
     93   int n = to_integer(p->value);
     94   assert(n >= 0);
     95   recipe_ordinal surrounding_recipe = lookup_surrounding_recipe(default_recipe, n);
     96   if (surrounding_recipe == -1) return -1;
     97   set<recipe_ordinal> done;
     98   vector<recipe_ordinal> path;
     99   return lookup_name(x, surrounding_recipe, done, path);
    100 }
    101
    102 // If the recipe we need to lookup this name in doesn't have names done yet,
    103 // recursively call transform_names on it.
    104 int lookup_name(const reagent& x, const recipe_ordinal r, set<recipe_ordinal>& done, vector<recipe_ordinal>& path) {
    105   if (!Name[r].empty()) return Name[r][x.name];
    106   if (contains_key(done, r)) {
    107     raise << "can't compute address of '" << to_string(x) << "' because\n" << end();
    108     for (int i = 1;  i < SIZE(path);  ++i) {
    109       raise << path.at(i-1) << " requires computing names of " << path.at(i) << '\n' << end();
    110     }
    111     raise << path.at(SIZE(path)-1) << " requires computing names of " << r << "..ad infinitum\n" << end();
    112     return -1;
    113   }
    114   done.insert(r);
    115   path.push_back(r);
    116   transform_names(r);  // Not passing 'done' through. Might this somehow cause an infinite loop?
    117   assert(!Name[r].empty());
    118   return Name[r][x.name];
    119 }
    120
    121 recipe_ordinal lookup_surrounding_recipe(const recipe_ordinal r, int n) {
    122   if (n == 0) return r;
    123   if (!contains_key(Surrounding_space, r)) {
    124     raise << "don't know surrounding recipe of '" << get(Recipe, r).name << "'\n" << end();
    125     return -1;
    126   }
    127   assert(contains_key(Surrounding_space, r));
    128   return lookup_surrounding_recipe(get(Surrounding_space, r), n-1);
    129 }
    130
    131 //: weaken use-before-set detection just a tad
    132 :(replace{} "bool already_transformed(const reagent& r, const map<string, int>& names)")
    133 bool already_transformed(const reagent& r, const map<string, int>& names) {
    134   if (has_property(r, "space")) {
    135     string_tree* p = property(r, "space");
    136     if (!p || !p->atom) {
    137       raise << "/space property should have exactly one (non-negative integer) value in '" << r.original_string << "'\n" << end();
    138       return false;
    139     }
    140     if (p->value != "0") return true;
    141   }
    142   return contains_key(names, r.name);
    143 }
    144
    145 :(scenario missing_surrounding_space)
    146 % Hide_errors = true;
    147 def f [
    148   local-scope
    149   x:num/space:1 <- copy 34
    150 ]
    151 +error: don't know surrounding recipe of 'f'
    152 +error: f: can't find a place to store 'x'
    153
    154 //: extra test for try_reclaim_locals() from previous layers
    155 :(scenario local_scope_ignores_nonlocal_spaces)
    156 def new-scope [
    157   local-scope
    158   x:&:num <- new number:type
    159   *x:&:num <- copy 34
    160   return default-space:space
    161 ]
    162 def use-scope [
    163   local-scope
    164   outer:space/names:new-scope <- next-ingredient
    165   0:space/names:new-scope <- copy outer:space
    166   return *x:&:num/space:1
    167 ]
    168 def main [
    169   1:space/raw <- new-scope
    170   3:num/raw <- use-scope 1:space/raw
    171 ]
    172 +mem: storing 34 in location 3
    173
    174 :(scenario recursive_transform_names)
    175 def foo [
    176   local-scope
    177   x:num <- copy 0
    178   return default-space:space/names:foo
    179 ]
    180 def main [
    181   local-scope
    182   0:space/names:foo <- foo
    183   x:num/space:1 <- copy 34
    184 ]
    185 $error: 0