Fix MinGW termination callbacks not being invoked

Author: Amanieu

src/rtstartup/rsbegin.rs

@@ -60,37 +60,36 @@ pub mod eh_frames {
     }
 
     // Unwind info registration/deregistration routines.
-    // See the docs of `unwind` module in libstd.
+    // See the docs of libpanic_unwind.
     extern "C" {
         fn rust_eh_register_frames(eh_frame_begin: *const u8, object: *mut u8);
         fn rust_eh_unregister_frames(eh_frame_begin: *const u8, object: *mut u8);
     }
 
-    unsafe fn init() {
+    unsafe extern "C" fn init() {
         // register unwind info on module startup
         rust_eh_register_frames(&__EH_FRAME_BEGIN__ as *const u8, &mut OBJ as *mut _ as *mut u8);
     }
 
-    unsafe fn uninit() {
+    unsafe extern "C" fn uninit() {
         // unregister on shutdown
         rust_eh_unregister_frames(&__EH_FRAME_BEGIN__ as *const u8, &mut OBJ as *mut _ as *mut u8);
     }
 
-    // MSVC-specific init/uninit routine registration
-    pub mod ms_init {
-        // .CRT$X?? sections are roughly analogous to ELF's .init_array and .fini_array,
-        // except that they exploit the fact that linker will sort them alphabitically,
-        // so e.g., sections with names between .CRT$XIA and .CRT$XIZ are guaranteed to be
-        // placed between those two, without requiring any ordering of objects on the linker
-        // command line.
-        // Note that ordering of same-named sections from different objects is not guaranteed.
-        // Since .CRT$XIA contains init array's header symbol, which must always come first,
-        // we place our initialization callback into .CRT$XIB.
+    // MinGW-specific init/uninit routine registration
+    pub mod mingw_init {
+        // MinGW's startup objects (crt0.o / dllcrt0.o) will invoke global constructors in the
+        // .ctors and .dtors sections on startup and exit. In the case of DLLs, this is done when
+        // the DLL is loaded and unloaded.
+        //
+        // The linker will sort the sections, which ensures that our callbacks are located at the
+        // end of the list. Since constructors are run in reverse order, this ensures that our
+        // callbacks are the first and last ones executed.
 
-        #[link_section = ".CRT$XIB"] // .CRT$XI? : C initialization callbacks
-        pub static P_INIT: unsafe fn() = super::init;
+        #[link_section = ".ctors.65535"] // .ctors.* : C initialization callbacks
+        pub static P_INIT: unsafe extern "C" fn() = super::init;
 
-        #[link_section = ".CRT$XTY"] // .CRT$XT? : C termination callbacks
-        pub static P_UNINIT: unsafe fn() = super::uninit;
+        #[link_section = ".dtors.65535"] // .dtors.* : C termination callbacks
+        pub static P_UNINIT: unsafe extern "C" fn() = super::uninit;
     }
 }