chore: Override the position of the expanded macro

Author: robertoraggi

src/frontend/cxx/frontend.cc

@@ -87,7 +87,11 @@ void dumpTokens(const CLI& cli, TranslationUnit& unit, std::ostream& output) {
       kind = Lexer::classifyKeyword(tk.spell());
     }
 
-    output << std::format("{} '{}'{}\n", Token::name(kind), tk.spell(), flags);
+    output << std::format("{} '{}'{}", Token::name(kind), tk.spell(), flags);
+
+    auto pos = unit.tokenStartPosition(loc);
+
+    output << std::format(" at {}:{}:{}\n", pos.fileName, pos.line, pos.column);
 
     if (tk.is(TokenKind::T_EOF_SYMBOL)) break;
   }

src/parser/cxx/preprocessor.cc

@@ -378,6 +378,12 @@ struct Tok final : Managed {
     return tk;
   }
 
+  [[nodiscard]] static auto Copy(Arena *pool, const Tok *tok) {
+    auto tk = new (pool) Tok();
+    *tk = *tok;
+    return tk;
+  }
+
   [[nodiscard]] static auto Gen(Arena *pool, TokenKind kind,
                                 const std::string_view &text,
                                 const Hideset *hideset = nullptr) -> Tok * {
@@ -826,6 +832,11 @@ struct Preprocessor::Private {
     return Tok::Gen(&pool_, kind, text, hideset);
   }
 
+  [[nodiscard]] auto copy(const Tok *tok) -> Tok * {
+    auto copy = Tok::Copy(&pool_, tok);
+    return copy;
+  }
+
   void pushState(std::tuple<bool, bool> state) {
     auto [skipping, evaluating] = state;
     skipping_.push_back(skipping);
@@ -2113,6 +2124,8 @@ auto Preprocessor::Private::substitute(TokList *pointOfSubstitution,
   TokList *os = nullptr;
   auto **ip = (&os);
 
+  std::unordered_set<const Tok *> macroTokens;
+
   auto appendTokens = [&](TokList *rs) {
     if (!*ip) {
       *ip = (rs);
@@ -2122,9 +2135,30 @@ auto Preprocessor::Private::substitute(TokList *pointOfSubstitution,
     while (*ip && (*ip)->next) ip = (&(*ip)->next);
   };
 
-  auto appendToken = [&](const Tok *tk) { appendTokens(cons(tk)); };
+  auto appendToken = [&](const Tok *tk) {
+    if (macroTokens.contains(tk)) {
+      // todo: make a copy of tk and override its location to be the same as
+      // the point of substitution.
+      auto copyTk = copy(tk);
+      copyTk->sourceFile = pointOfSubstitution->tok->sourceFile;
+      copyTk->offset = pointOfSubstitution->tok->offset;
+      copyTk->length = pointOfSubstitution->tok->length;
+      appendTokens(cons(copyTk));
+    } else {
+      appendTokens(cons(tk));
+    }
+  };
+
+  TokList *macroBody = getMacroBody(*macro);
+
+  for (auto it = macroBody; it; it = it->next) {
+    macroTokens.insert(it->tok);
+  }
+
+  // std::cerr << std::format("macro body has {} tokens\n", macroTokens.size());
 
-  TokList *ts = getMacroBody(*macro);
+  // set the token stream to the macro body
+  TokList *ts = macroBody;
 
   while (ts && !lookat(ts, TokenKind::T_EOF_SYMBOL)) {
     if (lookat(ts, TokenKind::T_HASH, TokenKind::T_IDENTIFIER)) {

tests/unit_tests/preprocessor/define.001.cc

@@ -7,4 +7,4 @@ int main() {
   return result;
 }
 
-// CHECK: int result = 0;
+// CHECK: int result = 0 ;

tests/unit_tests/preprocessor/define.002.cc

@@ -9,4 +9,4 @@ int main() {
   return result;
 }
 
-// CHECK: int result = 1;
+// CHECK: int result = 1 ;

tests/unit_tests/preprocessor/define.003.cc

@@ -9,4 +9,4 @@
 
 int main() { FOR_EACH(DECLARE_VAR) }
 
-// CHECK: int aa;int bb;int cc;
+// CHECK: int aa ; int bb ; int cc ;

tests/unit_tests/preprocessor/warning.001.cc

@@ -10,4 +10,4 @@
 const char* platform = PLATFORM;
 #endif
 
-// CHECK: const char* platform = "linux";
+// CHECK: const char* platform = "linux" ;