fix(instrument_drop_win): UTF-8 temp path, PID collision guard, embed-strip excluded from drop hotspot

src/instrument_drop_win.cpp

@@ -31,27 +31,49 @@ namespace reasampler {
 
 namespace {
 
-// Write `bytes` to a fresh uniquely-named .vstpreset in the OS temp dir and return its
-// absolute path; empty string on any failure. The .vstpreset extension is load-bearing —
+// Write `bytes` to a fresh uniquely-named .vstpreset in the OS temp dir and return its path;
+// returns an empty path on any failure. The .vstpreset extension is load-bearing —
 // TrackFX_SetPreset's full-path form is documented for .vstpreset files (VST3). The file is
 // transient: the caller deletes it right after the SetPreset call.
-std::string writeTempPreset(const std::vector<std::uint8_t>& bytes) {
-    static std::atomic<unsigned> counter{0};
-    std::error_code ec;
-    const std::filesystem::path dir = std::filesystem::temp_directory_path(ec);
-    if (ec) return {};
-    const std::filesystem::path path =
-        dir / ("reasampler_drop_" + std::to_string(counter.fetch_add(1)) + ".vstpreset");
-    std::ofstream out(path, std::ios::binary | std::ios::trunc);
-    if (!out) return {};
-    out.write(reinterpret_cast<const char*>(bytes.data()),
-              static_cast<std::streamsize>(bytes.size()));
-    out.close();
-    if (!out) {  // short write / flush failure -> don't hand REAPER a truncated preset
-        std::filesystem::remove(path, ec);
+//
+// The temp filename embeds the process ID so two concurrent REAPER instances (e.g. stable +
+// beta) cannot collide in the shared OS temp dir, and one instance's cleanup cannot
+// accidentally delete another's in-flight file.
+//
+// Non-throwing: every std::filesystem call uses the error_code overload. The whole body is
+// wrapped in try/catch to guarantee no exception crosses the REAPER C callback boundary
+// (the same discipline persist.cpp uses — see its non-throwing scanPruneOrphans comment).
+//
+// Returns the path object (not a narrow string) so the caller can:
+//   (a) pass path.u8string() to TrackFX_SetPreset — UTF-8 on MSVC, not ACP-converted,
+//       so a temp dir with accented or CJK user-name bytes is handled correctly;
+//   (b) delete via the retained path object — not via re-parsing the narrow string —
+//       so the cleanup cannot leak if the conversion above were to round-trip incorrectly.
+std::filesystem::path writeTempPreset(const std::vector<std::uint8_t>& bytes) {
+    try {
+        static std::atomic<unsigned> counter{0};
+        std::error_code ec;
+        const std::filesystem::path dir = std::filesystem::temp_directory_path(ec);
+        if (ec) return {};
+        // PID in the name keeps files from distinct REAPER instances distinct in the shared
+        // temp dir — prevents cross-instance collisions and spurious post-apply deletions.
+        const std::string name =
+            "reasampler_drop_" + std::to_string(GetCurrentProcessId()) +
+            "_" + std::to_string(counter.fetch_add(1)) + ".vstpreset";
+        const std::filesystem::path path = dir / name;
+        std::ofstream out(path, std::ios::binary | std::ios::trunc);
+        if (!out) return {};
+        out.write(reinterpret_cast<const char*>(bytes.data()),
+                  static_cast<std::streamsize>(bytes.size()));
+        out.close();
+        if (!out) {  // short write / flush failure -> don't hand REAPER a truncated preset
+            std::filesystem::remove(path, ec);
+            return {};
+        }
+        return path;
+    } catch (...) {
         return {};
     }
-    return path.string();
 }
 
 }  // namespace
@@ -77,7 +99,7 @@ bool loadInstrumentOntoTrack(MediaTrack* track, const std::vector<std::uint8_t>&
 
     // Materialize the .vstpreset FIRST so an I/O failure leaves the track untouched (no FX
     // added yet — nothing to roll back).
-    const std::string presetPath = writeTempPreset(presetBytes);
+    const std::filesystem::path presetPath = writeTempPreset(presetBytes);
     if (presetPath.empty()) return false;
 
     // The CHANNEL-correct FX name: "VST3:ReaSampler 9000" on stable, "VST3:ReaSampler 9000
@@ -100,9 +122,14 @@ bool loadInstrumentOntoTrack(MediaTrack* track, const std::vector<std::uint8_t>&
     // serializer produced (instrument_drop::buildInstrumentDropPreset ->
     // sample_map::serializeComponentState). Unlike the former "vst_chunk" named-config-parm
     // write, a failure here is REPORTED (false), not silently ignored.
-    if (ok) ok = TrackFX_SetPreset(track, fxIndex, presetPath.c_str());
+    //
+    // u8string() gives UTF-8 bytes on MSVC (not ACP-converted), so a temp dir under an
+    // accented or CJK user-name is handled correctly by REAPER's path APIs.
+    if (ok) ok = TrackFX_SetPreset(track, fxIndex, presetPath.u8string().c_str());
 
-    // The preset file is transient regardless of outcome; best-effort cleanup (temp dir).
+    // The preset file is transient regardless of outcome; delete via the retained path object
+    // (not a re-parsed narrow string) so cleanup cannot leak even if the UTF-8 conversion
+    // round-trip were incorrect.
     std::error_code ec;
     std::filesystem::remove(presetPath, ec);