Add Zinc RuntimeID Mask for portability

Changes

@@ -220,7 +220,8 @@ ___________
 
 - #13???: Introduce a RuntimeID for use in filename mangling to allow different
   configurations and different versions of ocamlrun and the shared runtime
-  libraries to coexist harmoniously on a single system.
+  libraries to coexist harmoniously on a single system. A portable version is
+  used in launcher header for bytecode executables.
   (David Allsopp, review by ???)
 
 ### Code generation and optimizations:

Makefile

@@ -29,7 +29,7 @@ defaultentry: $(DEFAULT_BUILD_TARGET)
 
 include stdlib/StdlibModules
 
-RUNTIME_NAME = $(BINDIR)/ocamlrun-$(BYTECODE_RUNTIME_ID)$(EXE)
+RUNTIME_NAME = $(BINDIR)/ocamlrun-$(ZINC_RUNTIME_ID)$(EXE)
 CAMLC = $(BOOT_OCAMLC) $(BOOT_STDLIBFLAGS) \
         -use-prims runtime/primitives \
         -use-runtime '$(subst ','\'',$(RUNTIME_NAME))'
@@ -2703,7 +2703,7 @@ install::
     $(LN) "$(TARGET)-$(1)-$(BYTECODE_RUNTIME_ID)$(EXE)" "$(1)$(EXE)"
 	cd "$(INSTALL_BINDIR)" && \
     $(LN) "$(TARGET)-$(1)-$(BYTECODE_RUNTIME_ID)$(EXE)" \
-	    "$(1)-$(BYTECODE_RUNTIME_ID)$(EXE)"
+	    "$(1)-$(ZINC_RUNTIME_ID)$(EXE)"
 endef
 define INSTALL_RUNTIME_LIB
 ifeq "$(2)" "BYTECODE"

Makefile.build_config.in

@@ -186,3 +186,4 @@ TSAN_NATIVE_RUNTIME_C_SOURCES = @tsan_native_runtime_c_sources@
 
 # OCaml release number, relative to 3.12 (used for RuntimeID)
 OCAML_RELEASE_NUMBER = @OCAML_RELEASE_NUMBER@
+ZINC_RUNTIME_ID = @zinc_runtime_id@

bytecomp/bytelink.ml

@@ -395,7 +395,7 @@ let write_header outchan =
     else
       let runtime =
         Printf.sprintf "ocamlrun%s-%s"
-                       !Clflags.runtime_variant Config.bytecode_runtime_id
+                       !Clflags.runtime_variant Config.zinc_runtime_id
       in
       Filename.concat runtime_info.bindir runtime
   in

configure.ac

@@ -260,6 +260,7 @@ AC_SUBST([QS])
 AC_SUBST([ar_supports_response_files])
 AC_SUBST([bytecode_runtime_id])
 AC_SUBST([native_runtime_id])
+AC_SUBST([zinc_runtime_id])
 
 ## Generated files
 
@@ -2723,6 +2724,7 @@ quintet3_native="$(echo "${alphabet}" | cut -c $(expr ${quintet3_native} + 1))"
 
 bytecode_runtime_id="${quintet3_byte}${quintet2}${quintet1}QUINTET0"
 native_runtime_id="${quintet3_native}${quintet2}${quintet1}QUINTET0"
+zinc_runtime_id="00${quintet1}QUINTET0"
 
 # Do not permanently cache the result of flexdll.h
 unset ac_cv_header_flexdll_h

runtime/Mangling.md

@@ -49,14 +49,16 @@ OCaml 5.x series.
 ## Masks
 
 A particular configuration of the compiler has one RuntimeID, but this is used
-in two different contexts where certain bits are masked out:
+in three different contexts where certain bits are masked out:
 
 1. Bytecode Mask (0xe7fff) is used by `libcamlrun` and masks out the frame
    pointers and spacetime bits since these affect neither the runtime nor code
    generation in bytecode.
 2. Native Mask (0xfffff) is used by `libasmrun`. Note that in native code, the
    only place where name mangling is used is natdynlink, and bit 8 is therefore
    _never_ set.
+3. Zinc Mask (0x001ff) is used by `ocamlc` for bytecode executables which do not
+   contain their own runtime.
 
 ## File Name Mangling
 
@@ -73,10 +75,33 @@ Mangling is applied to the name of any file which will be loaded at runtime:
 
 - `ocamlrun` (and variants) are triplet-prefixed and Bytecode-suffixed. A
   symbolic is created both for `ocamlrun` and for `ocamlrun` Byte-suffixed but
-  not triplet-prefixed.
+  not triplet-prefixed. See below for additional symbolic links which are
+  created.
 - C stub libraries loaded by both the bytecode runtime and bytecode `Dynlink`.
   These are triplet-prefixed and Bytecode-suffixed. The effect is that any
   runtime attempts to load stub libraries compiled for exactly the same runtime.
 - Shared versions of the bytecode and native runtimes (`libcamlrun_shared.so`
   and `libasmrun_shared.so`). These are triplet-prefixed and
   Bytecode/Native-suffixed respectively.
+
+Bytecode executables compiled without their runtime pose an additional challenge
+as these are portable. When a bytecode image is produced, the Zinc runtime ID is
+used to mangle the name of the runtime with Bit 7 set if the bytecode image does
+not require 63 bit `int` support (i.e. if the image compiles without error with
+`ocamlc -compat-32` then Bit 7 will be set in the RuntimeID, even with a 64-bit
+`ocamlc`) and Bit 8 unset. The runtime variant is then Zinc-suffixed to create
+the runtime name for the executable's header. For example, if OCaml 5.1 is
+configured with `--disable-flat-float-array --disable-shared` (Runtime suffix
+`8093`) then an executable not requiring 63-bit `int`s will use `ocamlrun-0053`
+as the runtime name. The "Zinc" RuntimeID here creates a portable and
+reproducible runtime name. In order to facilitate this, the following additional
+symbolic names are created, for each variant `<ocamlrun>`, with no
+triplet-prefix:
+
+- Zinc-suffixed
+- For runtimes supporting 63-bit `int` values, Zinc-suffixed but with Bit 7 set
+  (i.e. a 64-bit OCaml runtime also advertises that it works for 32-bit)
+
+Additionally, the header for the bytecode executable will initially search for a
+runtime with Bit 8 un-set (i.e. with a preference for runtimes supporting shared
+libraries) and fallback to searching for one with Bit 8 set otherwise.

utils/config.fixed.ml

@@ -56,6 +56,7 @@ let align_int64 = true
 let function_sections = false
 let afl_instrument = false
 let bytecode_runtime_id = ""
+let zinc_runtime_id = ""
 let native_runtime_id = ""
 let native_compiler = false
 let tsan = false

utils/config.generated.ml.in

@@ -69,6 +69,7 @@ let function_sections = @function_sections@
 let afl_instrument = @afl@
 
 let bytecode_runtime_id = {@QS@|@bytecode_runtime_id@|@QS@}
+let zinc_runtime_id = {@QS@|@zinc_runtime_id@|@QS@}
 let native_runtime_id = {@QS@|@native_runtime_id@|@QS@}
 
 let native_compiler = @native_compiler@

utils/config.mli

@@ -271,6 +271,12 @@ val bytecode_runtime_id : string
 
     @since 5.3 *)
 
+val zinc_runtime_id : string
+(** {!bytecode_runtime_id} with the Zinc Mask (used in headers to refer portably
+    to ocamlrun)
+
+    @since 5.3 *)
+
 val native_runtime_id : string
 (** The RuntimeID for libasmrun_shared