Add a clang64 chain for Unix-CLI compilers targeting the MSVC ABI

CHANGES

@@ -4,6 +4,16 @@ Next version
   (Nicolás Ojeda Bär, review by David Allsopp)
 - GRP#169: Drop the .llvm_addrsig section from rewritten objects.
   (Antonin Décimo, review by David Allsopp)
+- New `clang64` chain for C compilers with a Unix-style command line targeting
+  the MSVC ABI and runtime, such as `clang --target=x86_64-pc-windows-msvc` and
+  `zig cc -target x86_64-windows-msvc`. By default the link is driven through
+  the C compiler with an lld-link-style linker (lld), and `-Wl,/option`-style
+  arguments are now recognized and forwarded. A linker with a GNU-style command
+  line given with `-use-linker` (e.g. `-use-linker "ld.lld -m i386pep"`) is
+  instead invoked directly with GNU option spellings. Note that GNU binutils ld
+  is currently unable to link the MSVC CRT (it selects the wrong members from
+  msvcrt.lib).
+  (Antonin Décimo)
 
 Version 0.44
 - GPR#127: Recognise hyphens in option names in the COFF .drectve section.

Compat.ml.in

@@ -106,8 +106,8 @@
 
 407:module Stdlib = Pervasives
 
-404:module String = struct
-404:  include String
+405:module String = struct
+405:  include String
 402:
 402:  let init n f =
 402:    let s = create n in
@@ -131,7 +131,13 @@
 404:      end
 404:    done;
 404:    sub s 0 !j :: !r
-404:end
+405:
+405:  let rec index_rec_opt s lim i c =
+405:    if i >= lim then None else
+405:      if unsafe_get s i = c then Some i else index_rec_opt s lim (i + 1) c
+405:
+405:  let index_opt s c = index_rec_opt s (length s) 0 c
+405:end
 
 401:module Sys = struct
 401:  include Sys
@@ -141,6 +147,34 @@
 401:  let unix = (Sys.os_type = "Unix")
 401:end
 
+404:module Filename = struct
+404:  include Filename
+404:
+404:  let is_dir_sep s i =
+404:    if Sys.unix then s.[i] = '/'
+404:    else if Sys.win32 || Sys.cygwin then
+404:      let c = s.[i] in
+404:      c = '/' || c = '\\' || c = ':' && i = 1
+404:    else false
+404:
+404:  let extension_len name =
+404:    let rec check i0 i =
+404:      if i < 0 || is_dir_sep name i then 0
+404:      else if name.[i] = '.' then check i0 (i - 1)
+404:      else String.length name - i0
+404:    in
+404:    let rec search_dot i =
+404:      if i < 0 || is_dir_sep name i then 0
+404:      else if name.[i] = '.' then check i (i - 1)
+404:      else search_dot (i - 1)
+404:    in
+404:    search_dot (String.length name - 1)
+404:
+404:  let remove_extension name =
+404:    let l = extension_len name in
+404:    if l = 0 then name else String.sub name 0 (String.length name - l)
+404:end
+
 402:type bytes = string
 402:let output_bytes = output_string
 

Makefile

@@ -37,6 +37,10 @@ MIN64CC = $(MINGW64_PREFIX)gcc
 CYGWIN64_PREFIX = x86_64-pc-cygwin-
 CYG64CC = $(CYGWIN64_PREFIX)gcc
 
+# A C compiler with a Unix-style CLI targeting the MSVC ABI/CRT
+# (e.g. clang --target=x86_64-pc-windows-msvc, zig cc)
+CLANG64CC = clang --target=x86_64-pc-windows-msvc
+
 version.ml: Makefile flexdll.opam
 	echo 'let version = "$(VERSION)"' > $@
 	echo 'let mingw_prefix = "$(MINGW_PREFIX)"' >> $@
@@ -47,6 +51,7 @@ version.ml: Makefile flexdll.opam
 	echo 'let mingw = "$(notdir $(MINCC))"' >> $@
 	echo 'let mingw64 = "$(notdir $(MIN64CC))"' >> $@
 	echo 'let gnat = "gcc"' >> $@
+	echo 'let clang64 = "$(CLANG64CC)"' >> $@
 
 # Supported tool-chains
 
@@ -151,6 +156,7 @@ support: $(addprefix build_, $(CHAINS))
 build_gnat: flexdll_gnat.o flexdll_initer_gnat.o
 build_msvc: flexdll_msvc.obj flexdll_initer_msvc.obj
 build_msvc64: flexdll_msvc64.obj flexdll_initer_msvc64.obj
+build_clang64: flexdll_clang64.o flexdll_initer_clang64.o
 build_cygwin64: flexdll_cygwin64.o flexdll_initer_cygwin64.o
 build_mingw: flexdll_mingw.o flexdll_initer_mingw.o
 build_mingw64: flexdll_mingw64.o flexdll_initer_mingw64.o
@@ -215,6 +221,13 @@ flexdll_msvc.obj: flexdll.c flexdll.h
 flexdll_msvc64.obj: flexdll.c flexdll.h
 	$(MSVC64_PREFIX) $(MSVCC64) $(MSVC_FLAGS) /DMSVC /DMSVC64 -c /Fo"$@" $<
 
+# -fms-runtime-lib=dll matches the /MD of MSVC_FLAGS (the objects must not
+# carry a -defaultlib:libcmt directive)
+CLANG64_FLAGS = $(GCC_FLAGS) -fms-runtime-lib=dll -D_CRT_SECURE_NO_DEPRECATE
+
+flexdll_clang64.o: flexdll.c flexdll.h
+	$(CLANG64CC) $(CLANG64_FLAGS) -DMSVC -DMSVC64 -c -o $@ $<
+
 flexdll_cygwin64.o: flexdll.c flexdll.h
 	$(CYG64CC) $(GCC_FLAGS) -DCYGWIN -c -o $@ $<
 
@@ -233,6 +246,9 @@ flexdll_initer_msvc.obj: flexdll_initer.c
 flexdll_initer_msvc64.obj: flexdll_initer.c
 	$(MSVC64_PREFIX) $(MSVCC64) $(MSVC_FLAGS) -c /Fo"$@" $<
 
+flexdll_initer_clang64.o: flexdll_initer.c
+	$(CLANG64CC) $(CLANG64_FLAGS) -c -o $@ $<
+
 flexdll_initer_cygwin64.o: flexdll_initer.c
 	$(CYG64CC) $(GCC_FLAGS) -c -o $@ $<
 
@@ -263,6 +279,9 @@ demo_mingw64: flexlink.exe flexdll_mingw64.o flexdll_initer_mingw64.o
 demo_msvc64:  flexlink.exe flexdll_msvc64.obj flexdll_initer_msvc64.obj
 	$(MSVC64_PREFIX) $(MAKE) -C test clean demo CHAIN=msvc64 CC="$(MSVCC64)" CFLAGS="$(MSVC_FLAGS)" PLUG2_CFLAGS="/bigobj" O=obj
 
+demo_clang64: flexlink.exe flexdll_clang64.o flexdll_initer_clang64.o
+	$(MAKE) -C test clean demo CHAIN=clang64 CC="$(CLANG64CC)" CFLAGS="$(CLANG64_FLAGS)" O=o
+
 distclean: clean
 	rm -f Makefile.winsdk
 

README.md

@@ -63,6 +63,13 @@ MSVC: the 32-bit C compiler from Microsoft.
 
 MSVC64: the 64-bit C compiler from Microsoft.
 
+CLANG64: a 64-bit C compiler with a Unix-style command line targeting the
+MSVC ABI and runtime (e.g. `clang --target=x86_64-pc-windows-msvc` or
+`zig cc -target x86_64-windows-msvc`). By default the link is driven
+through the C compiler with an lld-link-style linker; a linker with a
+GNU-style command line passed with `-use-linker` (e.g.
+`-use-linker "ld.lld -m i386pep"`) is invoked directly instead.
+
 CYGWIN64: the 64-bit gcc compiler shipped with Cygwin.
 
 MINGW: the 32-bit gcc compiler from the MinGW-w64 project, packaged in

cmdline.ml

@@ -20,7 +20,7 @@ let use_default_libs = ref true
 let subsystem = ref "console"
 let explain = ref false
 let builtin_linker = ref false
-let toolchain : [ `MSVC | `MSVC64 | `MINGW | `MINGW64 | `GNAT | `GNAT64 | `CYGWIN64 | `LIGHTLD ] ref = ref `MSVC
+let toolchain : [ `MSVC | `MSVC64 | `CLANG64 | `MINGW | `MINGW64 | `GNAT | `GNAT64 | `CYGWIN64 | `LIGHTLD ] ref = ref `MSVC
 let use_linker = ref None
 let use_mt = ref None
 let save_temps = ref false
@@ -103,12 +103,13 @@ let specs = [
   "-l", Arg.String (fun s -> files := ("-l" ^ s) :: !files),
   "<lib> Library file";
 
-  "-chain", Arg.Symbol (["msvc";"msvc64";"cygwin64";"mingw";"mingw64";"gnat";"gnat64";"ld"],
+  "-chain", Arg.Symbol (["msvc";"msvc64";"clang64";"cygwin64";"mingw";"mingw64";"gnat";"gnat64";"ld"],
 			(fun s ->
                           machine := `x86; underscore := true;
                           toolchain := match s with
 			  | "msvc" -> `MSVC
 			  | "msvc64" -> machine := `x64; underscore := false; `MSVC64
+			  | "clang64" -> machine := `x64; underscore := false; `CLANG64
 			  | "cygwin64" -> machine := `x64; underscore := false; `CYGWIN64
 			  | "mingw" -> `MINGW
 			  | "gnat" -> `GNAT
@@ -277,8 +278,12 @@ let parse_cmdline () =
         String.sub s 0 2 :: String.sub s 2 (String.length s - 2) :: tr rest
     | s :: rest when String.length s >= 5 && String.sub s 0 5 = "/link" ->
         "-link" :: String.sub s 5 (String.length s - 5) :: tr rest
-    (* Convert gcc linker option prefix -Wl, to flexlink linker prefix -link *)
-    | s :: rest when String.length s >= 6 && String.sub s 0 5 = "-Wl,-" ->
+    (* Convert gcc linker option prefix -Wl, to flexlink linker prefix -link.
+       Also accept MSVC-style option spellings after -Wl, (e.g. -Wl,/entry:Sym,
+       as used with the clang64 chain) which would otherwise be mangled by the
+       -opt:value splitting below. *)
+    | s :: rest when String.length s >= 5 && String.sub s 0 4 = "-Wl,"
+                     && (s.[4] = '-' || s.[4] = '/') ->
         let args =
           String.split_on_char ',' (String.sub s 4 (String.length s - 4))
         in