From 057e9bf4da72df5f00bb1a1ae6de3f9154de234b Mon Sep 17 00:00:00 2001
From: mstembera <5421953+mstembera@users.noreply.github.com>
Date: Thu, 16 Jul 2026 08:17:21 +0200
Subject: [PATCH] Fix an MSVC debug break
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With the latest master I started getting:
"A breakpoint instruction (__debugbreak() statement or a similar call) was executed in Stockfish.exe." when debugging in MSVC.

I don't really understand the issue but Fable fixed it and I verified it works.
Here is its summary:
Bug: Calling _get_wpgmptr() in CommandLine::get_binary_directory() triggered a debug CRT assertion failure (__debugbreak()) on Windows. The CRT only initializes the wide program name _wpgmptr when the application uses a wide entry point (wmain). Since Stockfish uses the narrow main(int, char**) entry point, _wpgmptr remains nullptr, and the debug CRT's parameter validation asserts when _get_wpgmptr is called.

Fix: Replaced _get_wpgmptr() with GetModuleFileNameW(), which queries the executable path directly from the OS and does not depend on the CRT entry point type. The implementation uses a grow-and-retry loop, so paths longer than MAX_PATH are handled correctly. If the API fails, the code falls back to the original argv0-based behavior. The #ifdef _MSC_VER guard was also removed, since the fix no longer relies on the MSVC CRT — non-MSVC Windows builds (e.g., MinGW) now benefit from the accurate path as well.

closes https://github.com/official-stockfish/Stockfish/pull/6972

No functional change
---
 src/misc.cpp | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/misc.cpp b/src/misc.cpp
index dc6dee47f..27762ad4b 100644
--- a/src/misc.cpp
+++ b/src/misc.cpp
@@ -577,12 +577,15 @@ bool is_whitespace(std::string_view s) {
 fs::path CommandLine::get_binary_directory(fs::path argv0) {
 
 #ifdef _WIN32
-    #ifdef _MSC_VER
-    // Prefer the executable path reported by the CRT when available.
-    wchar_t* pgmptr = nullptr;
-    if (!_get_wpgmptr(&pgmptr) && pgmptr != nullptr && *pgmptr)
-        argv0 = fs::path(pgmptr);
-    #endif
+    // Prefer the executable path reported by Windows. Unlike _get_wpgmptr,
+    // this does not depend on whether the CRT used a narrow or wide entry
+    // point. Windows paths cannot exceed 32767 characters, so a fixed
+    // buffer is always sufficient. Falls back to argv0 if the API fails.
+    constexpr DWORD MaxPath = 32768;
+    wchar_t         path[MaxPath];
+
+    if (const DWORD length = GetModuleFileNameW(nullptr, path, MaxPath))
+        argv0 = fs::path(path, path + length);
 #endif
 
     auto binaryDirectory = argv0.parent_path();