build: Add support for Clang-CL

mcfgthread/gthr_aux.c

@@ -45,21 +45,25 @@ __MCF_gthr_do_call_once_seh_take_over(_MCF_once* once, __MCF_cxa_dtor_any_ init_
 "  push esi  \n"
 "  push ebp  \n"
 "  mov ebp, esp  \n"
-/* Install an SEH handler.  */
+"  sub esp, 20  \n"
+/* Initialize the constant zero.  */
 "  xor esi, esi  \n"
-"  push OFFSET _do_call_once_seh_uhandler  \n"
-"  push fs:[esi]  \n"
-"  mov fs:[esi], esp  \n"
+/* Install an SEH handler.  */
+"  mov eax, fs:[esi]  \n"
+"  lea ecx, [ebp - 8]  \n"
+"  mov [ecx], eax  \n"
+"  mov eax, OFFSET _do_call_once_seh_uhandler  \n"
+"  mov [ecx + 4], eax  \n"
+"  mov fs:[esi], ecx  \n"
 /* Make the call `(*init_proc) (arg)`. The argument is passed
  * both via the ECX register and on the stack, to allow both
  * `__cdecl` and `__thiscall` functions to work properly.  */
 "  mov ecx, [ebp + 20]  \n"
-"  sub esp, 8  \n"
-"  push ecx  \n"
+"  mov [ebp - 20], ecx  \n"
 "  call [ebp + 16]  \n"
-"  add esp, 12  \n"
 /* Dismantle the SEH handler.  */
-"  pop fs:[esi]  \n"
+"  mov eax, [ebp - 8]  \n"
+"  mov fs:[esi], eax  \n"
 /* Disarm the once flag with a tail call.  */
 "  leave  \n"
 "  pop esi  \n"

meson.build

@@ -185,9 +185,15 @@ mcfgthread_version_o = import('windows').compile_resources(
 lib_mcfgthread_c_args = [
       '-ffreestanding', '-fasynchronous-unwind-tables' ]
 
-lib_mcfgthread_dll_link_args = [
-      '-nostdlib', '-Wl,-enable-auto-image-base', '-Wl,-subsystem,windows:6.1',
-      '-Wl,-exclude-all-symbols', '-Wl,-kill-at', '-Wl,-gc-sections' ]
+if cc.get_linker_id() in [ 'link', 'lld-link' ]
+  lib_mcfgthread_dll_link_args = [
+        '-Wl,-nodefaultlib', '-Wl,-dynamicbase', '-Wl,-opt:ref', '-Wl,-opt:icf',
+        '-Xlinker', '-subsystem:windows,6.1' ]
+else
+  lib_mcfgthread_dll_link_args = [
+        '-nostdlib', '-Wl,-enable-auto-image-base', '-Wl,-gc-sections',
+        '-Wl,-subsystem,windows:6.1', '-Wl,-exclude-all-symbols', '-Wl,-kill-at' ]
+endif
 
 lib_mcfgthread_minimal_dll = shared_library('mcfgthread-minimal',
       c_pch: 'mcfgthread/xprecompiled.h',

meson.native.clang-cl

@@ -0,0 +1,9 @@
+[built-in options]
+cpp_std = 'c++14'
+
+[binaries]
+c = 'clang'
+cpp = 'clang++'
+ar = 'llvm-ar'
+strip = 'llvm-strip'
+windres = 'llvm-rc'