diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3e9962a..170f78a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,10 @@
 cmake_minimum_required(VERSION 3.13)
+
+if (NOT CMAKE_BUILD_TYPE)
+    set(CMAKE_BUILD_TYPE "Debug" CACHE STRING
+            "Build type options: Debug Release RelWithDebInfo MinSizeRel" FORCE)
+endif ()
+
 project(wibo LANGUAGES CXX)
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
@@ -6,7 +12,7 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 find_package(Filesystem REQUIRED)
 
 set(CMAKE_CXX_STANDARD 17)
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m32 -Wall -g")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m32 -Wall")
 include_directories(.)
 add_executable(wibo
     dll/advapi32.cpp
diff --git a/Dockerfile b/Dockerfile
index 54943b1..d1c1dab 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -8,8 +8,7 @@ RUN apk add --no-cache cmake ninja g++ linux-headers binutils
 COPY . /wibo
 
 # Build static binary
-# Replace with RelWithDebInfo when -O2 crash is fixed
-RUN cmake -S /wibo -B /wibo/build -G Ninja -DCMAKE_BUILD_TYPE=Debug -DCMAKE_CXX_FLAGS="-static" \
+RUN cmake -S /wibo -B /wibo/build -G Ninja -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_FLAGS="-static" \
     && cmake --build /wibo/build \
     && strip -g /wibo/build/wibo
 
diff --git a/common.h b/common.h
index a73e3e6..5c2cda5 100644
--- a/common.h
+++ b/common.h
@@ -6,7 +6,10 @@
 #include <unistd.h>
 #include <assert.h>
 
-#define WIN_FUNC __attribute__((stdcall))
+// On Windows, the incoming stack is aligned to a 4 byte boundary.
+// force_align_arg_pointer will realign the stack to match GCC's 16 byte alignment.
+#define WIN_ENTRY __attribute__((force_align_arg_pointer))
+#define WIN_FUNC WIN_ENTRY __attribute__((stdcall))
 #define DEBUG_LOG(...) wibo::debug_log(__VA_ARGS__)
 
 namespace user32 {
diff --git a/dll/kernel32.cpp b/dll/kernel32.cpp
index 83fff2f..658644c 100644
--- a/dll/kernel32.cpp
+++ b/dll/kernel32.cpp
@@ -933,17 +933,45 @@ namespace kernel32 {
 	}
 
 	unsigned int WIN_FUNC GetSystemDirectoryA(char *lpBuffer, unsigned int uSize) {
-		strcpy(lpBuffer, "C:\\Windows\\System32");
-		return strlen(lpBuffer);
+		DEBUG_LOG("GetSystemDirectoryA(%p, %u)\n", lpBuffer, uSize);
+		if (lpBuffer == nullptr) {
+			return 0;
+		}
+
+		const char* systemDir = "C:\\Windows\\System32";
+		const auto len = strlen(systemDir);
+
+		// If the buffer is too small, return the required buffer size.
+		// (Add 1 to include the NUL terminator)
+		if (uSize < len + 1) {
+			return len + 1;
+		}
+
+		strcpy(lpBuffer, systemDir);
+		return len;
 	}
 
 	unsigned int WIN_FUNC GetWindowsDirectoryA(char *lpBuffer, unsigned int uSize) {
-		strcpy(lpBuffer, "C:\\Windows");
-		return strlen(lpBuffer);
+		DEBUG_LOG("GetWindowsDirectoryA(%p, %u)\n", lpBuffer, uSize);
+		if (lpBuffer == nullptr) {
+			return 0;
+		}
+
+		const char* systemDir = "C:\\Windows";
+		const auto len = strlen(systemDir);
+
+		// If the buffer is too small, return the required buffer size.
+		// (Add 1 to include the NUL terminator)
+		if (uSize < len + 1) {
+			return len + 1;
+		}
+
+		strcpy(lpBuffer, systemDir);
+		return len;
 	}
 
 	unsigned int WIN_FUNC GetCurrentDirectoryA(unsigned int uSize, char *lpBuffer) {
-		DEBUG_LOG("GetCurrentDirectoryA\n");
+		DEBUG_LOG("GetCurrentDirectoryA(%u, %p)\n", uSize, lpBuffer);
 
 		std::filesystem::path cwd = std::filesystem::current_path();
 		std::string path = files::pathToWindows(cwd);
diff --git a/dll/lmgr.cpp b/dll/lmgr.cpp
index 866f4de..9a65919 100644
--- a/dll/lmgr.cpp
+++ b/dll/lmgr.cpp
@@ -1,13 +1,13 @@
 #include "common.h"
 
 namespace lmgr {
-	int lp_checkout(int a, int b, const char* c, const char* d, int e, const char* f, int* out) {
+	int WIN_ENTRY lp_checkout(int a, int b, const char* c, const char* d, int e, const char* f, int* out) {
 		DEBUG_LOG("lp_checkout %d %d %s %s %d %s\n", a, b, c, d, e, f);
 		*out = 1234;
 		return 0;
 	}
 
-	int lp_checkin() {
+	int WIN_ENTRY lp_checkin() {
 		DEBUG_LOG("lp_checkin\n");
 		return 0;
 	}