From f5dfc264ba806ac96b2b2caa2d10da5d38695aec Mon Sep 17 00:00:00 2001
From: Quantum <quantum2048@gmail.com>
Date: Wed, 21 Jul 2021 01:30:13 -0400
Subject: [PATCH] [host] windows: trick MinGW into not using memcpy from ntdll

MinGW seems to decide at random whether it wants to use memcpy from
mscvrt.dll or ntdll.dll. Currently, on Debian buster, ntdll.dll is chosen,
while on sid, mscvrt.dll is chosen.

This commit declares a new .def file for ntdll containing only the
functions we want to link from ntdll.dll, and generates ntdll.a from it
with dlltool. This way, MinGW will never be tempted to link functions
like memcpy from ntdll.dll.
---
 host/platform/Windows/CMakeLists.txt | 16 ++++++++++++++++
 host/platform/Windows/ntdll.def      |  7 +++++++
 2 files changed, 23 insertions(+)
 create mode 100644 host/platform/Windows/ntdll.def

diff --git a/host/platform/Windows/CMakeLists.txt b/host/platform/Windows/CMakeLists.txt
index 32b93c75..cd2f784b 100644
--- a/host/platform/Windows/CMakeLists.txt
+++ b/host/platform/Windows/CMakeLists.txt
@@ -18,6 +18,22 @@ add_compile_definitions(WINVER=0x0601 _WIN32_WINNT=0x0601)
 
 add_subdirectory("capture")
 
+if (MINGW)
+	# Build our own ntdll.dll import library
+	# This tricks MinGW into not linking stuff like memcpy from ntdll.dll instead of mscvrt.dll
+	find_program(DLLTOOL_EXECUTABLE NAMES "x86_64-w64-mingw32-dlltool" "dlltool.exe" DOC "dlltool executable")
+	add_custom_command(OUTPUT "${PROJECT_BINARY_DIR}/ntdll.a"
+		COMMAND "${DLLTOOL_EXECUTABLE}" -d "${PROJECT_SOURCE_DIR}/ntdll.def" -l "${PROJECT_BINARY_DIR}/ntdll.a"
+		MAIN_DEPENDENCY "${PROJECT_SOURCE_DIR}/ntdll.def"
+		COMMENT "Building import library ntdll.a"
+		VERBATIM
+	)
+	add_custom_target(ntdll_target DEPENDS "${PROJECT_BINARY_DIR}/ntdll.a")
+	add_library(ntdll STATIC IMPORTED GLOBAL)
+	add_dependencies(ntdll ntdll_target)
+	set_target_properties(ntdll PROPERTIES IMPORTED_LOCATION "${PROJECT_BINARY_DIR}/ntdll.a")
+endif()
+
 target_link_libraries(platform_Windows
 	lg_common
 	capture
diff --git a/host/platform/Windows/ntdll.def b/host/platform/Windows/ntdll.def
new file mode 100644
index 00000000..310184d0
--- /dev/null
+++ b/host/platform/Windows/ntdll.def
@@ -0,0 +1,7 @@
+; This file is used to trick MinGW to not like stuff like memcpy from ntdll.dll.
+; See CMakeLists.txt for how this is compiled.
+
+LIBRARY "ntdll.dll"
+EXPORTS
+NtDelayExecution
+NtSetTimerResolution