Allow libdir to be found relative to bindir

When configured with --enable-relative, the runtime uses the directory
of the executable to determine the location of the Standard Library.
Thus, ocamlrun and the compilers look for ../lib/ocaml by default.

This is implemented by changing caml_standard_library_default to be a
relative path, and then computing the actual value at startup (for
bytecode) and when queried (for native, since it is only ever used if
Dynlink is being used).

Executables (and objects) produced by the compiler always have an
absolute value of caml_standard_library_default. ocamlc.opt and
ocamlopt.opt are built using -set-global-string to force
caml_standard_library_default to stay a relative value.

.depend

@@ -2336,6 +2336,7 @@ bytecomp/bytelink.cmo : \
     utils/consistbl.cmi \
     utils/config.cmi \
     utils/compression.cmi \
+    driver/compenv.cmi \
     file_formats/cmo_format.cmi \
     utils/clflags.cmi \
     utils/ccomp.cmi \
@@ -2355,6 +2356,7 @@ bytecomp/bytelink.cmx : \
     utils/consistbl.cmx \
     utils/config.cmx \
     utils/compression.cmx \
+    driver/compenv.cmx \
     file_formats/cmo_format.cmi \
     utils/clflags.cmx \
     utils/ccomp.cmx \
@@ -2750,6 +2752,7 @@ asmcomp/asmlink.cmo : \
     utils/consistbl.cmi \
     utils/config.cmi \
     middle_end/compilenv.cmi \
+    driver/compenv.cmi \
     file_formats/cmx_format.cmi \
     asmcomp/cmm_helpers.cmi \
     asmcomp/cmm.cmi \
@@ -2771,6 +2774,7 @@ asmcomp/asmlink.cmx : \
     utils/consistbl.cmx \
     utils/config.cmx \
     middle_end/compilenv.cmx \
+    driver/compenv.cmx \
     file_formats/cmx_format.cmi \
     asmcomp/cmm_helpers.cmx \
     asmcomp/cmm.cmx \

Changes

@@ -161,6 +161,12 @@ ___________
   runtime assertions.
   (Antonin Décimo, review by Miod Vallat, Gabriel Scherer, and David Allsopp)
 
+- #13???: Added --enable-relative which allows the runtime and the compilers to
+  locate the Standard Library relative to where the binaries themselves,
+  removing the absolute path previously embedded in
+  caml_standard_library_default.
+  (David Allsopp, review by ???)
+
 ### Code generation and optimizations:
 
 - #13014: Enable compile-time option -function-sections on all previously

Makefile

@@ -1429,15 +1429,22 @@ C_LITERAL = $(shell $(SAK) encode-C-literal '$(1)')
 
 runtime/build_config.h: $(ROOTDIR)/Makefile.config $(SAK)
 	$(V_GEN)echo '/* This file is generated from $(ROOTDIR)/Makefile.config */' > $@ && \
-	echo '#define OCAML_STDLIB_DIR $(call C_LITERAL,$(LIBDIR))' >> $@ && \
-	echo '#define HOST "$(HOST)"' >> $@
+	echo '#define OCAML_STDLIB_DIR $(call C_LITERAL,$(LIBDIR))' >> $@
+ifneq "$(LIBDIR_REL)" ""
+	@echo '#define OCAML_STDLIB_DIR_REL $(call C_LITERAL,$(LIBDIR_REL))' >> $@
+endif
+	@echo '#define HOST "$(HOST)"' >> $@
+
+runtime/stdlib.$(O): runtime/build_config.h
 
 ## Runtime libraries and programs
 
-runtime/ocamlrun$(EXE): runtime/prims.$(O) runtime/libcamlrun.$(A)
+runtime/ocamlrun$(EXE): runtime/prims.$(O) runtime/stdlib.$(O) \
+                        runtime/libcamlrun.$(A)
 	$(V_MKEXE)$(MKEXE) -o $@ $^ $(BYTECCLIBS)
 
-runtime/ocamlruns$(EXE): runtime/prims.$(O) runtime/libcamlrun_non_shared.$(A)
+runtime/ocamlruns$(EXE): runtime/prims.$(O) runtime/stdlib.$(O) \
+                         runtime/libcamlrun_non_shared.$(A)
 	$(V_MKEXE)$(call MKEXE_VIA_CC,$@,$^ $(BYTECCLIBS))
 
 runtime/libcamlrun.$(A): $(libcamlrun_OBJECTS)
@@ -1446,13 +1453,15 @@ runtime/libcamlrun.$(A): $(libcamlrun_OBJECTS)
 runtime/libcamlrun_non_shared.$(A): $(libcamlrun_non_shared_OBJECTS)
 	$(V_MKLIB)$(call MKLIB,$@, $^)
 
-runtime/ocamlrund$(EXE): runtime/prims.$(O) runtime/libcamlrund.$(A)
+runtime/ocamlrund$(EXE): runtime/prims.$(O) runtime/stdlib.$(O) \
+                         runtime/libcamlrund.$(A)
 	$(V_MKEXE)$(MKEXE) $(MKEXEDEBUGFLAG) -o $@ $^ $(BYTECCLIBS)
 
 runtime/libcamlrund.$(A): $(libcamlrund_OBJECTS)
 	$(V_MKLIB)$(call MKLIB,$@, $^)
 
-runtime/ocamlruni$(EXE): runtime/prims.$(O) runtime/libcamlruni.$(A)
+runtime/ocamlruni$(EXE): runtime/prims.$(O) runtime/stdlib.$(O) \
+                         runtime/libcamlruni.$(A)
 	$(V_MKEXE)$(MKEXE) -o $@ $^ $(INSTRUMENTED_RUNTIME_LIBS) $(BYTECCLIBS)
 
 runtime/libcamlruni.$(A): $(libcamlruni_OBJECTS)

Makefile.build_config.in

@@ -183,3 +183,5 @@ TSAN=@tsan@
 # Contains TSan-specific runtime files, or nothing if TSan support is
 # disabled
 TSAN_NATIVE_RUNTIME_C_SOURCES = @tsan_native_runtime_c_sources@
+
+RELOCATABLE = @relocatable@

Makefile.common

@@ -156,6 +156,15 @@ ifeq "$(FUNCTION_SECTIONS)" "true"
 OPTCOMPFLAGS += -function-sections
 endif
 
+ifeq "$(LIBDIR_REL)" ""
+  SET_RELATIVE_STDLIB =
+else
+  SET_RELATIVE_STDLIB = \
+-set-global-string 'caml_standard_library_default=$(LIBDIR_REL)'
+endif
+
+DOTOPT_LINKFLAGS = $(SET_RELATIVE_STDLIB)
+
 # The rule to compile C files
 
 # This rule is similar to GNU make's implicit rule, except that it is more
@@ -360,6 +369,7 @@ $(basename $(notdir $(1)))_NATIVE_LINKFLAGS =
 $(basename $(notdir $(1)))_NATIVE_LINKCMD = \
 $(strip \
   $$(CAMLOPT) $$(OC_COMMON_LINKFLAGS) $$(OC_NATIVE_LINKFLAGS) \
+  $(DOTOPT_LINKFLAGS) \
   $$($(basename $(notdir $(1)))_COMMON_LINKFLAGS) \
   $$($(basename $(notdir $(1)))_NATIVE_LINKFLAGS))
 

asmcomp/asmlink.ml

@@ -335,6 +335,7 @@ let link ~ppf_dump objfiles output_name =
     let obj_infos = List.map read_file objfiles in
     let ldeps = Linkdeps.create ~complete:true in
     let units_tolink = List.fold_right (scan_file ldeps) obj_infos [] in
+    Compenv.set_caml_standard_library_default ();
     (match Linkdeps.check ldeps with
      | None -> ()
      | Some e -> raise (Error (Link_error e)));

bytecomp/bytelink.ml

@@ -780,6 +780,8 @@ let link objfiles output_name =
   Clflags.all_ccopts := !lib_ccopts @ !Clflags.all_ccopts;
                                                    (* put user's opts first *)
   Clflags.dllibs := !lib_dllibs @ !Clflags.dllibs; (* put user's DLLs first *)
+  if !Clflags.custom_runtime then
+    Compenv.set_caml_standard_library_default ();
   if not !Clflags.custom_runtime then begin
     assert (!Clflags.global_string_constants = []);
     link_bytecode tolink output_name true

bytecomp/dll.ml

@@ -143,7 +143,8 @@ let synchronize_primitive num symb =
 let ld_conf_contents () =
   let path = ref [] in
   begin try
-    let ic = open_in (Filename.concat Config.standard_library "ld.conf") in
+    let ic =
+      open_in (Filename.concat Config.standard_library_effective "ld.conf") in
     begin try
       while true do
         path := input_line ic :: !path

configure.ac

@@ -84,6 +84,7 @@ ocamltest_unix_impl="dummy"
 unix_library=""
 unix_directory=""
 bindir_to_libdir=''
+relocatable=no
 
 # Information about the package
 
@@ -257,6 +258,7 @@ AC_SUBST([ocaml_libdir])
 AC_SUBST([QS])
 AC_SUBST([ar_supports_response_files])
 AC_SUBST([bindir_to_libdir])
+AC_SUBST([relocatable])
 
 ## Generated files
 
@@ -1169,6 +1171,7 @@ AS_CASE([$host],
   [AC_CHECK_HEADERS([unistd.h],[AC_DEFINE([HAS_UNISTD], [1])])])
 
 AC_CHECK_HEADER([math.h])
+AC_CHECK_HEADERS([unistd.h],[AC_DEFINE([HAS_UNISTD])])
 AC_CHECK_HEADER([pthread_np.h],[AC_DEFINE([HAS_PTHREAD_NP_H], [1])])
 AC_CHECK_HEADER([dirent.h], [AC_DEFINE([HAS_DIRENT], [1])], [],
   [#include <sys/types.h>])
@@ -2645,6 +2648,7 @@ AS_IF([test x"$mandir" = x'${datarootdir}/man'],
   [mandir='${prefix}/man'])
 
 AS_IF([test x"$enable_relative" = "xyes"],[
+  relocatable=yes
   OCAML_COMPUTE_BINDIR_TO_LIBDIR([bindir],[libdir],[bindir_to_libdir])
   dnl Tests for the OCAML_COMPUTE_BINDIR_TO_LIBDIR macro
   dnl OCAML_COMPUTE_BINDIR_TO_LIBDIR_TESTS

driver/compenv.ml

@@ -732,3 +732,10 @@ let parse_arguments ?(current=ref 0) argv f program =
         Printf.sprintf "Usage: %s <options> <files>\nOptions are:" program in
       Printf.printf "%s\n%s" help_msg err_msg;
       raise (Exit_with_status 0)
+
+let set_caml_standard_library_default () =
+  let symbol = "caml_standard_library_default" in
+  if not (List.exists (fun (name, _) -> name = symbol)
+                      !global_string_constants) then
+    global_string_constants :=
+      (symbol, Config.standard_library_effective) :: !global_string_constants

driver/compenv.mli

@@ -76,3 +76,7 @@ val process_deferred_actions :
 *)
 val parse_arguments : ?current:(int ref)
       -> string array ref -> Arg.anon_fun -> string -> unit
+
+(** Adds caml_standard_library_default to {!Clflags.global_string_constants}
+    if it isn't already present. *)
+val set_caml_standard_library_default: unit -> unit

runtime/caml/dynlink.h

@@ -41,9 +41,6 @@ extern void caml_build_primitive_table_builtin(void);
 /* Unload all the previously loaded shared libraries */
 extern void caml_free_shared_libs(void);
 
-/* Return the effective location of the standard library */
-extern char_os * caml_get_stdlib_location(void);
-
 /* Parse ld.conf and add the lines read to caml_shared_libs_path */
 extern char_os * caml_parse_ld_conf(void);
 

runtime/caml/osdeps.h

@@ -142,6 +142,14 @@ CAMLextern clock_t caml_win32_clock(void);
 
 CAMLextern value caml_win32_xdg_defaults(void);
 
+#define CAML_DIR_SEP T("\\")
+#define Is_dir_separator(c) (c == '\\' || c == '/')
+
+#else
+
+#define CAML_DIR_SEP "/"
+#define Is_dir_separator(c) (c == '/')
+
 #endif /* _WIN32 */
 
 /* Returns the current value of a counter that increments once per nanosecond.
@@ -155,6 +163,18 @@ extern uint64_t caml_time_counter(void);
 
 extern void caml_init_os_params(void);
 
+/* True if:
+   - dir equals "."
+   - dir equals ".."
+   - dir begins "./"
+   - dir begins "../"
+   The tests for null avoid the need to call strlen_os. */
+#define Is_relative_dir(dir) \
+  (dir[0] == '.' \
+   && (dir[1] == 0 \
+       || Is_dir_separator(dir[1]) \
+       || (dir[1] == '.' && (dir[2] == 0 || Is_dir_separator(dir[2])))))
+
 #endif /* CAML_INTERNALS */
 
 #ifdef _WIN32

runtime/caml/s.h.in

@@ -112,6 +112,10 @@
 
 /* Define HAS_UNISTD if you have /usr/include/unistd.h. */
 
+#undef HAS_LIBGEN_H
+
+/* Define HAS_LIBGEN_H if you have /usr/include/libgen.h. */
+
 #undef HAS_DIRENT
 
 /* Define HAS_DIRENT if you have /usr/include/dirent.h and the result of

runtime/caml/sys.h

@@ -34,9 +34,15 @@ CAMLnoret CAMLextern void caml_sys_io_error (value);
 
 CAMLextern double caml_sys_time_unboxed(value);
 CAMLextern void caml_sys_init (char_os * exe_name, char_os ** argv);
+CAMLextern void caml_locate_standard_library (const char_os *);
 
 CAMLnoret CAMLextern void caml_do_exit (int);
 
+extern char_os * caml_standard_library_default;
+extern char_os * caml_standard_library_relative;
+extern char_os * caml_standard_library;
+extern char_os *_Atomic caml_relative_root_dir;
+
 #ifdef __cplusplus
 }
 #endif

runtime/dynlink.c

@@ -40,6 +40,7 @@
 #include "caml/signals.h"
 #include "caml/intext.h"
 #include "caml/startup.h"
+#include "caml/sys.h"
 
 #include "build_config.h"
 
@@ -88,7 +89,7 @@ CAMLexport char_os * caml_get_stdlib_location(void)
   char_os * stdlib;
   stdlib = caml_secure_getenv(T("OCAMLLIB"));
   if (stdlib == NULL) stdlib = caml_secure_getenv(T("CAMLLIB"));
-  if (stdlib == NULL) stdlib = OCAML_STDLIB_DIR;
+  if (stdlib == NULL) stdlib = caml_standard_library;
   return stdlib;
 }
 

runtime/startup_byt.c

@@ -383,9 +383,7 @@ static void do_print_config(void)
   /* Print the runtime configuration */
   printf("version: %s\n", OCAML_VERSION_STRING);
   printf("standard_library_default: %s\n",
-         caml_stat_strdup_of_os(OCAML_STDLIB_DIR));
-  printf("standard_library: %s\n",
-         caml_stat_strdup_of_os(caml_get_stdlib_location()));
+         caml_stat_strdup_of_os(caml_standard_library_default));
   printf("int_size: %d\n", 8 * (int)sizeof(value));
   printf("word_size: %d\n", 8 * (int)sizeof(value) - 1);
   printf("os_type: %s\n", OCAML_OS_TYPE);
@@ -486,11 +484,14 @@ CAMLexport void caml_main(char_os **argv)
      With -custom, we have an executable that is ocamlrun itself
      concatenated with the bytecode.  So, if the attempt with argv[0]
      failed, it is worth trying again with executable_name. */
-  if (fd < 0 && (proc_self_exe = caml_executable_name()) != NULL) {
+  proc_self_exe = caml_executable_name();
+  if (fd < 0 && proc_self_exe != NULL) {
     exe_name = proc_self_exe;
     fd = caml_attempt_open(&exe_name, &trail, 0);
   }
 
+  caml_locate_standard_library(proc_self_exe ? proc_self_exe : exe_name);
+
   if (fd < 0) {
     pos = parse_command_line(argv);
     if (caml_params->print_config) {
@@ -622,6 +623,8 @@ CAMLexport value caml_startup_code_exn(
   exe_name = caml_executable_name();
   if (exe_name == NULL) exe_name = caml_search_exe_in_path(argv[0]);
 
+  caml_locate_standard_library(exe_name);
+
   Caml_state->external_raise = NULL;
   /* Setup signal handling */
   caml_init_signals();

runtime/stdlib.c

@@ -0,0 +1,22 @@
+/**************************************************************************/
+/*                                                                        */
+/*                                 OCaml                                  */
+/*                                                                        */
+/*                 David Allsopp, OCaml Labs, Cambridge.                  */
+/*                                                                        */
+/*   Copyright 2021 David Allsopp Ltd.                                    */
+/*                                                                        */
+/*   All rights reserved.  This file is distributed under the terms of    */
+/*   the GNU Lesser General Public License version 2.1, with the          */
+/*   special exception on linking described in the file LICENSE.          */
+/*                                                                        */
+/**************************************************************************/
+
+#include "caml/misc.h"
+#include "build_config.h"
+
+#if defined(OCAML_STDLIB_DIR_REL)
+char_os * caml_standard_library_default = OCAML_STDLIB_DIR_REL;
+#else
+char_os * caml_standard_library_default = OCAML_STDLIB_DIR;
+#endif