RAII the gzFile handle in KataGoParser

Own the gzFile with a custom-deleter unique_ptr so it closes on every
exit path (normal return, exception, bad_alloc); removes the manual
try/catch+gzclose in parse() and the ordering caveat on buffer allocation.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: ChinChangYang

cpp/external/katagocoreml/src/parser/KataGoParser.cpp

@@ -33,11 +33,11 @@ bool KataGoParser::isVersionSupported(int version) {
 // ============================================================================
 
 bool KataGoParser::refill() {
-    if(m_gz == nullptr) return false;
-    int n = gzread(m_gz, m_refill.data(), (unsigned)m_refill.size());
+    if(!m_gz) return false;
+    int n = gzread(m_gz.get(), m_refill.data(), (unsigned)m_refill.size());
     if(n < 0) {
         int errnum;
-        const char* errmsg = gzerror(m_gz, &errnum);
+        const char* errmsg = gzerror(m_gz.get(), &errnum);
         throw std::runtime_error("Error reading gzip stream: " + std::string(errmsg));
     }
     m_refillPos = 0;
@@ -72,27 +72,17 @@ void KataGoParser::readExact(uint8_t* dst, size_t n, const std::string& name) {
 // ============================================================================
 
 KataGoModelDesc KataGoParser::parse() {
-    // Allocate the refill buffer before opening the file so a bad_alloc here
-    // cannot leak an open gzFile handle.
+    // Allocate the refill buffer first; if this throws, no handle has been opened.
     m_refill.resize(1024 * 1024);
-    m_gz = gzopen(m_model_path.c_str(), "rb");
-    if(m_gz == nullptr)
+    m_gz.reset(gzopen(m_model_path.c_str(), "rb"));
+    if(!m_gz)
         throw std::runtime_error("Cannot open file: " + m_model_path);
     m_refillPos = 0;
     m_refillLen = 0;
     m_formatDetected = false;   // decided at first readFloats
     m_binary_floats = true;
-    KataGoModelDesc model;
-    try {
-        model = parseModel();
-    } catch(...) {
-        gzclose(m_gz);
-        m_gz = nullptr;
-        throw;
-    }
-    gzclose(m_gz);
-    m_gz = nullptr;
-    return model;
+    // ~GzHandle closes the file on normal return OR exception — no try/catch needed.
+    return parseModel();
 }
 
 // ============================================================================

cpp/external/katagocoreml/src/parser/KataGoParser.hpp

@@ -5,7 +5,9 @@
 
 #include "../types/KataGoTypes.hpp"
 #include <array>
+#include <memory>
 #include <string>
+#include <type_traits>
 #include <vector>
 #include <zlib.h>
 
@@ -32,7 +34,13 @@ class KataGoParser {
 
 private:
     std::string m_model_path;
-    gzFile m_gz = nullptr;
+    // Custom-deleter unique_ptr owns the gzFile so it closes on every exit path
+    // (normal return, exception, or bad_alloc) without manual try/catch.
+    struct GzCloser {
+        void operator()(gzFile f) const noexcept { if(f) gzclose(f); }
+    };
+    using GzHandle = std::unique_ptr<std::remove_pointer_t<gzFile>, GzCloser>;
+    GzHandle m_gz;
     std::vector<uint8_t> m_refill;   // bounded refill buffer (~1 MB)
     size_t m_refillPos = 0;          // read cursor within m_refill
     size_t m_refillLen = 0;          // valid bytes in m_refill