From fdaed322dfa84f735112792a0ab3d7d94690b14f Mon Sep 17 00:00:00 2001
From: Oliver Hamlet <git@ortham.net>
Date: Tue, 25 Mar 2025 19:33:53 +0000
Subject: [PATCH] Fix linking debug builds of C++ wrapper

---
 .cargo/msvcd-config.toml |  6 ++++++
 cxx/CMakeLists.txt       | 13 ++++++++-----
 cxx/README.md            |  8 ++++++++
 cxx/build.rs             | 13 ++++++++++++-
 4 files changed, 34 insertions(+), 6 deletions(-)
 create mode 100644 .cargo/msvcd-config.toml

diff --git a/.cargo/msvcd-config.toml b/.cargo/msvcd-config.toml
new file mode 100644
index 00000000..c2632a08
--- /dev/null
+++ b/.cargo/msvcd-config.toml
@@ -0,0 +1,6 @@
+# Config for building the CXX wrapper against the debug MSVC runtime, so that it
+# can be used from Debug builds of C++ code.
+# From <https://github.com/dtolnay/cxx/issues/880#issuecomment-2521375384>
+[env]
+CFLAGS = "/MDd"
+CXXFLAGS = "/MDd"
diff --git a/cxx/CMakeLists.txt b/cxx/CMakeLists.txt
index e1c6de29..68e71ae3 100644
--- a/cxx/CMakeLists.txt
+++ b/cxx/CMakeLists.txt
@@ -27,8 +27,13 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 add_library(libloot-cxx STATIC IMPORTED)
 # TODO: Define the Rust libloot library path here for Linux builds.
 if(MSVC)
-    set_target_properties(libloot-cxx PROPERTIES IMPORTED_LOCATION "${CMAKE_SOURCE_DIR}/../target/release/libloot_cxx.lib")
+    set(LIBLOOT_CXX_FILENAME "libloot_cxx.lib")
 endif()
+
+set_target_properties(libloot-cxx PROPERTIES
+    IMPORTED_CONFIGURATIONS "Release;Debug"
+    IMPORTED_LOCATION "${CMAKE_SOURCE_DIR}/../target/release/${LIBLOOT_CXX_FILENAME}"
+    IMPORTED_LOCATION_DEBUG "${CMAKE_SOURCE_DIR}/../target/debug/${LIBLOOT_CXX_FILENAME}")
 target_include_directories(libloot-cxx INTERFACE "${CMAKE_SOURCE_DIR}/../target/cxxbridge")
 
 
@@ -56,8 +61,7 @@ set(LIBLOOT_SRC_API_CPP_FILES
     "${CMAKE_SOURCE_DIR}/src/api/plugin.cpp"
     "${CMAKE_SOURCE_DIR}/src/api/sorting/cyclic_interaction_error.cpp"
     "${CMAKE_SOURCE_DIR}/src/api/sorting/undefined_group_error.cpp"
-    "${CMAKE_SOURCE_DIR}/src/api/vertex.cpp"
-    )
+    "${CMAKE_SOURCE_DIR}/src/api/vertex.cpp")
 
 set(LIBLOOT_INCLUDE_H_FILES
     "${CMAKE_SOURCE_DIR}/include/loot/api.h"
@@ -92,8 +96,7 @@ set(LIBLOOT_SRC_API_H_FILES
     "${CMAKE_SOURCE_DIR}/src/api/database.h"
     "${CMAKE_SOURCE_DIR}/src/api/exception.h"
     "${CMAKE_SOURCE_DIR}/src/api/game.h"
-    "${CMAKE_SOURCE_DIR}/src/api/plugin.h"
-    )
+    "${CMAKE_SOURCE_DIR}/src/api/plugin.h")
 
 source_group(TREE "${CMAKE_SOURCE_DIR}/src/api"
     PREFIX "Source Files"
diff --git a/cxx/README.md b/cxx/README.md
index 86821ad0..ff19250a 100644
--- a/cxx/README.md
+++ b/cxx/README.md
@@ -17,6 +17,14 @@ cmake -B build .
 cmake --build build --config RelWithDebInfo
 ```
 
+Debug builds need a little extra config to get the static and shared libraries to use the same C runtime library on Windows.
+
+```
+cargo build --config ../.cargo/msvcd-config.toml
+cmake -B build .
+cmake --build build --config Debug
+```
+
 This also builds a copy of the public API tests from C++ libloot v0.25.5, which can be run using:
 
 ```
diff --git a/cxx/build.rs b/cxx/build.rs
index 92388cc9..833a7145 100644
--- a/cxx/build.rs
+++ b/cxx/build.rs
@@ -3,5 +3,16 @@ fn main() {
         .std("c++17")
         .compile("libloot-cxx");
 
-    println!("cargo:rerun-if-changed=src/lib.rs");
+    // From <https://github.com/dtolnay/cxx/issues/880#issuecomment-2521375384>
+    if std::env::var("TARGET").is_ok_and(|s| s.contains("windows-msvc")) {
+        // MSVC compiler suite
+        if std::env::var("CFLAGS").is_ok_and(|s| s.contains("/MDd")) {
+            // debug runtime flag is set
+
+            // Don't link the default CRT
+            println!("cargo::rustc-link-arg=/nodefaultlib:msvcrt");
+            // Link the debug CRT instead
+            println!("cargo::rustc-link-arg=/defaultlib:msvcrtd");
+        }
+    }
 }