Statically link WebView2Loader - single exe, no DLL needed

build.rs swaps the dynamic import library with the static archive
from webview2-com-sys, so the WebView2 loader code is baked into
the exe. msvc_compat.rs provides the MSVC CRT symbols (security
cookie, thread-safe init, C++ operators) that the MSVC-compiled
static library expects.

src-tauri/src/lib.rs

@@ -1,4 +1,6 @@
 mod config;
+#[cfg(all(windows, target_env = "gnu"))]
+mod msvc_compat;
 mod stats;
 mod timer;
 

src-tauri/src/msvc_compat.rs

@@ -0,0 +1,98 @@
+//! Compatibility shims for MSVC CRT symbols required by WebView2LoaderStatic.lib.
+//!
+//! When statically linking the WebView2 loader on GNU/MinGW, the MSVC-compiled
+//! object code references these symbols. We provide minimal implementations so
+//! the linker can resolve them.
+
+use std::sync::atomic::{AtomicI32, Ordering};
+
+// ── MSVC Buffer Security Check (/GS) ────────────────────────────────────────
+//
+// MSVC's /GS flag instruments functions with stack canaries. These two symbols
+// implement the canary check. The cookie value is arbitrary — real MSVC CRT
+// randomises it at startup, but for a statically-linked helper library this
+// fixed sentinel is sufficient.
+
+#[no_mangle]
+pub static __security_cookie: u64 = 0x00002B992DDFA232;
+
+#[no_mangle]
+pub unsafe extern "C" fn __security_check_cookie(cookie: u64) {
+    if cookie != __security_cookie {
+        std::process::abort();
+    }
+}
+
+// ── MSVC Thread-Safe Static Initialisation ───────────────────────────────────
+//
+// C++11 guarantees that function-local statics are initialised exactly once,
+// even under concurrent access. MSVC implements this with an epoch counter and
+// a set of helper functions. The WebView2 loader uses a few statics internally.
+//
+// Simplified implementation: uses an atomic spin for the guard. This is safe
+// because WebView2 initialisation runs on the main thread in practice.
+
+#[no_mangle]
+pub static _Init_thread_epoch: AtomicI32 = AtomicI32::new(0);
+
+#[no_mangle]
+pub unsafe extern "C" fn _Init_thread_header(guard: *mut i32) {
+    if guard.is_null() {
+        return;
+    }
+    // Spin until we can claim the guard (-1 = uninitialized, 0 = done, 1 = in progress)
+    loop {
+        let val = guard.read_volatile();
+        if val == 0 {
+            // Already initialised — tell caller to skip
+            return;
+        }
+        if val == -1 {
+            // Not yet initialised — try to claim it
+            guard.write_volatile(1);
+            return;
+        }
+        // val == 1: another thread is initialising — yield and retry
+        std::thread::yield_now();
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn _Init_thread_footer(guard: *mut i32) {
+    if !guard.is_null() {
+        guard.write_volatile(0); // Mark initialisation complete
+        _Init_thread_epoch.fetch_add(1, Ordering::Release);
+    }
+}
+
+// ── MSVC C++ Runtime Operators (mangled names) ───────────────────────────────
+//
+// The static library is compiled with MSVC, which uses its own C++ name mangling.
+// MinGW's libstdc++ exports the same operators but with GCC/Itanium mangling,
+// so the linker can't match them. We provide the MSVC-mangled versions here.
+
+/// `std::nothrow` — MSVC-mangled `?nothrow@std@@3Unothrow_t@1@B`
+/// An empty struct constant used as a tag for nothrow `new`.
+#[export_name = "?nothrow@std@@3Unothrow_t@1@B"]
+pub static MSVC_STD_NOTHROW: u8 = 0;
+
+/// `operator new(size_t, const std::nothrow_t&)` — nothrow allocation
+/// MSVC-mangled: `??2@YAPEAX_KAEBUnothrow_t@std@@@Z`
+#[export_name = "??2@YAPEAX_KAEBUnothrow_t@std@@@Z"]
+pub unsafe extern "C" fn msvc_operator_new_nothrow(size: usize, _nothrow: *const u8) -> *mut u8 {
+    let size = if size == 0 { 1 } else { size };
+    let layout = std::alloc::Layout::from_size_align_unchecked(size, 8);
+    let ptr = std::alloc::alloc(layout);
+    ptr // null on failure — nothrow semantics
+}
+
+/// `operator delete(void*, size_t)` — sized deallocation
+/// MSVC-mangled: `??3@YAXPEAX_K@Z`
+#[export_name = "??3@YAXPEAX_K@Z"]
+pub unsafe extern "C" fn msvc_operator_delete_sized(ptr: *mut u8, size: usize) {
+    if !ptr.is_null() {
+        let size = if size == 0 { 1 } else { size };
+        let layout = std::alloc::Layout::from_size_align_unchecked(size, 8);
+        std::alloc::dealloc(ptr, layout);
+    }
+}