feat: C++ 阶段 2 - 命名空间支持

- namespace NAME { } 块扁平化: 跳过关键字, 内容按顶层解析
- 表达式/函数体中 ns::name -> name (非类名 + :: 跳过)
- 外部成员定义 ns::Class::method -> Class_method (跳命名空间限定)
- 支持嵌套命名空间 outer::inner::Class::method
- using namespace ns; / using ns::name; 跳过
- 修复: gather_decl 已消费首个 :: 的流位置不对称问题

tools/pcc-cpp.c

@@ -34,6 +34,7 @@ typedef struct {
 static FILE *g_in, *g_out;
 static Token g_tok;
 static int g_line = 1;
+static int g_ns_open = 0;   /* namespace block depth (flattened) */
 
 typedef struct ClassInfo {
     char name[128];
@@ -544,6 +545,16 @@ static void parse_member_decl(const char *cls, const char *ret_type, const char
             int prev_dot = 0;
             while (bd > 0) {
                 if (g_tok.type == T_EOF) break;
+                /* namespace-qualified name: ns::name -> name */
+                if (g_tok.type == T_IDENT && !find_class(g_tok.text)) {
+                    Token nxt;
+                    read_tok(&nxt);
+                    if (nxt.type == T_PUNCT && !strcmp(nxt.text, "::")) {
+                        next_tok();   /* consume '::' */
+                        continue;
+                    }
+                    unread_tok(&nxt);
+                }
                 if (g_tok.type == T_PUNCT && !strcmp(g_tok.text, "{")) { bd++; proto_emit(" {"); prev_dot = 0; next_tok(); continue; }
                 if (g_tok.type == T_PUNCT && !strcmp(g_tok.text, "}")) { bd--; if (bd > 0) proto_emit("}"); next_tok(); continue; }
                 if (g_tok.type == T_THIS) { proto_emit("this"); prev_dot = 0; next_tok(); continue; }
@@ -823,6 +834,26 @@ static void parse_member_definition(const char *ret_type)
     int is_ctor = 0, is_dtor = 0;
     ClassInfo *ci;
 
+    /* skip namespace qualifiers: math::Point::draw -> Point::draw.
+       gather_decl already consumed the first '::', so the stream is at
+       the second segment; if the first segment is not a class it is a
+       namespace prefix that must be dropped. */
+    if (g_tok.type == T_IDENT && !find_class(g_tok.text)) {
+        /* skip the first namespace segment (its '::' already consumed) */
+        next_tok();   /* g_tok = second segment */
+        /* skip remaining 'ns ::' pairs */
+        while (g_tok.type == T_IDENT && !find_class(g_tok.text)) {
+            Token nxt;
+            read_tok(&nxt);
+            if (nxt.type == T_PUNCT && !strcmp(nxt.text, "::")) {
+                next_tok();   /* g_tok = segment after '::' */
+                continue;
+            }
+            unread_tok(&nxt);
+            break;
+        }
+    }
+
     strncpy(cls, g_tok.text, sizeof cls - 1);
     cls[sizeof cls - 1] = 0;
     next_tok();
@@ -937,6 +968,16 @@ static void parse_member_definition(const char *ret_type)
         int prev_dot = 0;
         while (!(g_tok.type == T_PUNCT && !strcmp(g_tok.text, "}") && depth == 0)) {
             if (g_tok.type == T_EOF) break;
+            /* namespace-qualified name: ns::name -> name */
+            if (g_tok.type == T_IDENT && !find_class(g_tok.text)) {
+                Token nxt;
+                read_tok(&nxt);
+                if (nxt.type == T_PUNCT && !strcmp(nxt.text, "::")) {
+                    next_tok();   /* consume '::' */
+                    continue;
+                }
+                unread_tok(&nxt);
+            }
             if (g_tok.type == T_PUNCT && !strcmp(g_tok.text, "{")) { depth++; emit(" {"); prev_dot = 0; next_tok(); continue; }
             if (g_tok.type == T_PUNCT && !strcmp(g_tok.text, "}")) {
                 if (depth > 0) { depth--; emit("}"); next_tok(); continue; }
@@ -1207,6 +1248,16 @@ static void parse_free_operator(const char *ret_type, const char *name)
             while (!(g_tok.type == T_PUNCT && !strcmp(g_tok.text, "}") &&
                      bdepth == 0)) {
                 if (g_tok.type == T_EOF) break;
+                /* namespace-qualified name: ns::name -> name */
+                if (g_tok.type == T_IDENT && !find_class(g_tok.text)) {
+                    Token nxt;
+                    read_tok(&nxt);
+                    if (nxt.type == T_PUNCT && !strcmp(nxt.text, "::")) {
+                        next_tok();   /* consume '::' */
+                        continue;
+                    }
+                    unread_tok(&nxt);
+                }
                 if (g_tok.type == T_PUNCT && !strcmp(g_tok.text, "{")) {
                     bdepth++;
                     emit(" {");
@@ -1344,6 +1395,16 @@ static void parse_function(const char *ret_type, const char *name)
         next_tok();
         while (!(g_tok.type == T_PUNCT && !strcmp(g_tok.text, "}") && depth == 0)) {
             if (g_tok.type == T_EOF) break;
+            /* namespace-qualified name: ns::name -> name */
+            if (g_tok.type == T_IDENT && !find_class(g_tok.text)) {
+                Token nxt;
+                read_tok(&nxt);
+                if (nxt.type == T_PUNCT && !strcmp(nxt.text, "::")) {
+                    next_tok();   /* consume '::' */
+                    continue;
+                }
+                unread_tok(&nxt);
+            }
             if (g_tok.type == T_PUNCT && !strcmp(g_tok.text, "{")) { depth++; emit(" {"); next_tok(); continue; }
             if (g_tok.type == T_PUNCT && !strcmp(g_tok.text, "}")) {
                 if (depth > 0) { depth--; emit("}"); next_tok(); continue; }
@@ -1732,10 +1793,27 @@ static void parse_program(void)
             continue;
         }
 
-        if (g_tok.type == T_USING || g_tok.type == T_NAMESPACE ||
+        if (g_tok.type == T_NAMESPACE) {
-            g_tok.type == T_TEMPLATE || g_tok.type == T_INLINE ||
+            /* namespace NAME { ... } -> flattened: parse the body at
-            g_tok.type == T_CONSTEXPR || g_tok.type == T_FRIEND ||
+               top level; '}' (tracked by g_ns_open) closes it */
-            g_tok.type == T_VIRTUAL) {
+            next_tok();
+            if (g_tok.type == T_IDENT) next_tok();
+            if (g_tok.type == T_PUNCT && !strcmp(g_tok.text, "{")) {
+                next_tok();
+                g_ns_open++;
+            }
+            continue;
+        }
+        /* '}' closes a namespace block */
+        if (g_tok.type == T_PUNCT && !strcmp(g_tok.text, "}")) {
+            if (g_ns_open > 0) g_ns_open--;
+            next_tok();
+            continue;
+        }
+
+        if (g_tok.type == T_USING || g_tok.type == T_TEMPLATE ||
+            g_tok.type == T_INLINE || g_tok.type == T_CONSTEXPR ||
+            g_tok.type == T_FRIEND || g_tok.type == T_VIRTUAL) {
             next_tok();
             while (!(g_tok.type == T_EOF)) {
                 if (g_tok.type == T_PUNCT &&