From 4fe5acd08a1fe7778169d97da72586300ce5da0a Mon Sep 17 00:00:00 2001
From: fuhsnn <66062782+fuhsnn@users.noreply.github.com>
Date: Sat, 21 Dec 2024 00:47:22 +0800
Subject: [PATCH] Rework CondIncl objects

---
 preprocess.c | 58 +++++++++++++++++++++++++++++++++-------------------
 slimcc.h     |  2 +-
 2 files changed, 38 insertions(+), 22 deletions(-)

diff --git a/preprocess.c b/preprocess.c
index d0b19ec..68e171b 100644
--- a/preprocess.c
+++ b/preprocess.c
@@ -44,13 +44,17 @@ typedef struct {
 } MacroContext;
 
 // `#if` can be nested, so we use a stack to manage nested `#if`s.
-typedef struct CondIncl CondIncl;
-struct CondIncl {
-  CondIncl *next;
-  enum { IN_THEN, IN_ELIF, IN_ELSE } ctx;
+typedef struct {
   Token *tok;
+  enum { IN_THEN, IN_ELIF, IN_ELSE } ctx;
   bool included;
-};
+} CondIncl;
+
+static struct {
+  CondIncl *data;
+  int capacity;
+  int cnt;
+} cond_incl_stk;
 
 // A linked list of locked macros. Since macro nesting happens in
 // LIFO fashion (inner expansions end first), we only need to check
@@ -58,7 +62,6 @@ struct CondIncl {
 static Macro *locked_macros;
 
 static HashMap macros;
-static CondIncl *cond_incl;
 static HashMap pragma_once;
 static HashMap include_guards;
 
@@ -355,14 +358,21 @@ static int64_t eval_const_expr(Token *tok) {
   return val;
 }
 
-static CondIncl *push_cond_incl(Token *tok, bool included) {
-  CondIncl *ci = calloc(1, sizeof(CondIncl));
-  ci->next = cond_incl;
-  ci->ctx = IN_THEN;
-  ci->tok = tok;
-  ci->included = included;
-  cond_incl = ci;
-  return ci;
+static void push_cond_incl(Token *tok, bool included) {
+  int idx = cond_incl_stk.cnt++;
+  if (idx >= cond_incl_stk.capacity) {
+    cond_incl_stk.capacity = idx + 8;
+    cond_incl_stk.data = realloc(cond_incl_stk.data, sizeof(CondIncl) * cond_incl_stk.capacity);
+  }
+  cond_incl_stk.data[idx].ctx = IN_THEN;
+  cond_incl_stk.data[idx].tok = tok;
+  cond_incl_stk.data[idx].included = included;
+}
+
+static CondIncl *get_cond_incl(void) {
+  if (cond_incl_stk.cnt > 0)
+    return &cond_incl_stk.data[cond_incl_stk.cnt - 1];
+  return NULL;
 }
 
 static Macro *find_macro(Token *tok) {
@@ -951,8 +961,8 @@ static Token *include_file(Token *tok, char *path, Token *filename_tok, int *inc
     return tok;
 
   if (is_hash(start) && equal(start->next, "ifndef") &&
-      start->next->next->kind == TK_IDENT && equal(end, "endif"))
-    start->next->guard_file = end->guard_file = path;
+    start->next->next->kind == TK_IDENT && equal(end, "endif"))
+    start->next->is_incl_guard = end->is_incl_guard = true;
 
   end->next = tok;
   return start;
@@ -1168,9 +1178,11 @@ static Token *directives(Token **cur, Token *start) {
   }
 
   if (equal(tok, "elif")) {
+    CondIncl *cond_incl = get_cond_incl();
     if (!cond_incl || cond_incl->ctx == IN_ELSE)
       error_tok(start, "stray #elif");
     cond_incl->ctx = IN_ELIF;
+    cond_incl->tok->is_incl_guard = false;
 
     if (!cond_incl->included && eval_const_expr(split_line(&tok, tok->next)))
       cond_incl->included = true;
@@ -1180,9 +1192,11 @@ static Token *directives(Token **cur, Token *start) {
   }
 
   if (equal(tok, "else")) {
+    CondIncl *cond_incl = get_cond_incl();
     if (!cond_incl || cond_incl->ctx == IN_ELSE)
       error_tok(start, "stray #else");
     cond_incl->ctx = IN_ELSE;
+    cond_incl->tok->is_incl_guard = false;
     tok = skip_line(tok->next);
 
     if (cond_incl->included)
@@ -1191,16 +1205,18 @@ static Token *directives(Token **cur, Token *start) {
   }
 
   if (equal(tok, "endif")) {
+    CondIncl *cond_incl = get_cond_incl();
     if (!cond_incl)
       error_tok(start, "stray #endif");
 
-    if (tok->guard_file && tok->guard_file == cond_incl->tok->guard_file) {
+    if (tok->is_incl_guard && cond_incl->tok->is_incl_guard &&
+      tok->file == cond_incl->tok->file) {
       Token *name_tok = cond_incl->tok->next;
       char *guard_name = strndup(name_tok->loc, name_tok->len);
-      hashmap_put(&include_guards, tok->guard_file, guard_name);
+      hashmap_put(&include_guards, tok->file->name, guard_name);
     }
 
-    cond_incl = cond_incl->next;
+    cond_incl_stk.cnt--;
     tok = skip_line(tok->next);
     return tok;
   }
@@ -1700,8 +1716,8 @@ static Token *preprocess3(Token *tok) {
 // Entry point function of the preprocessor.
 Token *preprocess(Token *tok) {
   tok = preprocess2(tok);
-  if (cond_incl)
-    error_tok(cond_incl->tok, "unterminated conditional directive");
+  if (cond_incl_stk.cnt)
+    error_tok(get_cond_incl()->tok, "unterminated conditional directive");
 
   if (opt_E)
     return tok;
diff --git a/slimcc.h b/slimcc.h
index bc307e0..1f7c576 100644
--- a/slimcc.h
+++ b/slimcc.h
@@ -146,8 +146,8 @@ struct Token {
   bool at_bol;      // True if this token is at beginning of line
   bool has_space;   // True if this token follows a space character
   bool dont_expand; // True if a macro token is encountered during the macro's expansion
+  bool is_incl_guard;
   Token *origin;    // If this is expanded from a macro, the original token
-  char *guard_file; // The path of a potentially include-guarded file
   Token *attr_next;
 } PACKED;