Relocatable ocamlfind with sprinkles by dra27 · Pull Request #122 · ocaml/ocamlfind

dra27 · 2026-07-17T17:34:32Z

This PR both adapts ocamlfind for OCaml 5.5 and also extends it to be relocatable itself. Relocatable in this instance is according to my definition in ocaml/RFCs#53 - in practice, this means that where the system toolchain supports it, the installation of findlib to two different prefixes for the same compiler configuration should be byte-for-byte identical.

As with the finest of wines, it is best reviewed commit-by-commit:

The first commit partially winds back one of the changes made in Relocatable ocamlfind #72 for generating topfind by instead being able to generate the two files which Relocatable ocamlfind #72 merged. This paves the way for there being three variants. The trick instead is that lines which should be present in OCaml 4.00+ are prefixed 4x:
The next commit extends the semantics of findlib.conf to interpret relative paths. As noted in the commit message, paths are interpreted relative to findlib.conf or, for files loaded from findlib.conf.d, relative to the directory containing findlib.conf.d.
The next commit extends configure to support being configured for potentially relocatable builds. This is done by passing a relative path to -sitelib, which is interpreted relative to the location given for -config. That sounds rather complicated, but as can be seen in the opam file, it just means that where before we configured with -sitelib lib we now configure with -sitelib .. configure then computes the relative path of the directory containing findlib.conf from OCaml's Standard Library.
The next commit fixes ocamlfind warning "Cannot read directory ../stublibs which is mentioned in ld.conf" #115 by implementing the required support for reading the relative paths which OCaml 5.5+ uses in ld.conf.
As noted in Make paths from ld.conf absolute #119, the non-normalised paths that come out of processing the explicit relative paths are a problem for systems where ocamlfind updates ld.conf (it would just cause it to add multiple entries, though). The next commit puts the plumbing in to detect Unix.realpath and uses it on the resulting paths for comparisons.
The final two commits update CI the build to have the incantations required to produce a fully relocatable binary on Windows / macOS / Linux. I've technically implemented that support for GNU make only, because life's too short for POSIX make. CI for OCaml 5.5 creates a second switch (instantly, of course), pins ocamlfind in that switch as well and then verifies that the ocamlfind is identical.

Relative paths in findlib (including in `path`) are interpreted relative the directory containing findlib.conf or findlib.conf.d (interpreting relative paths of files in findlib.conf.d relative to the directory containing findlib.conf.d rather than to the file itself allows a findlib.conf path to be moved to/from findlib.conf.d without changing its semantics).

If -sitelib is passed a relative path, this is interpreted relative to the path used for findlib.conf (i.e. the path given for -config). For example, `./configure -config $(opam var lib)/findlib.conf -sitelib .` has the same meaning as passing `-sitelib $(opam var lib)`. If Relocatable OCaml is being used, and the OCaml Standard Library is in a directory underneath `-config` (as an opam switch does, for example), and the ocamlfind binary is being installed to the same directory as the compiler, then Relocatable Findlib is enabled. In mode, `ocamlfind` searches for `findlib.conf` relative to the location of OCaml's Standard Library and `topfind` similarly locates the `-sitelib` directory relative to OCaml's Standard Library. `findlib.conf` is also configured to use relative paths.

OCaml 5.4 interprets entries beginning with an explicit ./ or ../ as being relative to the directory containing ld.conf. ocamlfind recognises this too for the DLL consistency checks while ensuring that existing explicit-relative entries are preserved when ld.conf entries are being added.

When Findlib is configured to use a shared stublibs directory (which, in particular, is the configuration opam uses), ocamlfind checks to see that the shared stublibs directory is mentioned in ld.conf. Previously, this check tries to take into account path normalisation and case-insensitive file-systems, but the check is thwarted by OCaml 5.4's new explicit-relative lines in ld.conf (for opam, it therefore can't recognise that ../stublibs refers to `$(opam var lib)/stublibs`). OCaml 4.13+ has Unix.realpath, so we detect the presence of that and use it to canonicalise the paths. This works reliably because all the directories are known to exist at the point of the check. Earlier versions (which may also use the same ld.conf syntax owing to the Relocatable OCaml backports) will continue to display the innocuous warning.

Works around cloning problems in OCaml 5.5

shym

Thank you very much for that PR!
I’ve only a series of small comments and suggestions, everything very light.
And beware that, to paraphrase approximately Knuth, I’ve only read through this, not tested it…

shym · 2026-07-22T13:51:43Z

+
+#----------------------------------------------------------------------
+# For Relocatable Findlib, the path of site-lib relative to the OCaml
+# Standard Library directory. For normal Findlib, equal to


Suggested change

# Standard Library directory. For normal Findlib, equal to

# Standard Library directory. For non-relocatable Findlib, equal to

I’d like to see the relocatable version be the new normal one.

shym · 2026-07-22T13:51:43Z

+            elif [ "x$d1" = "x${d1#$d2}" ] || [ "x$d3" = "x{$d3##/}" ]; then
+                non_relocatable_reason="findlib.conf and the Standard Library don't share a common path"


Suggested change

elif [ "x$d1" = "x${d1#$d2}" ] || [ "x$d3" = "x{$d3##/}" ]; then

non_relocatable_reason="findlib.conf and the Standard Library don't share a common path"

elif [ "x$d1" = "x${d1#$d2/}" ]; then

non_relocatable_reason="findlib.conf and the Standard Library don't share a common path"

I think that combines both tests, namely detects whether stdlib is in a strict subdirectory of where findlib.conf will be located, or I’m mistaken?
I read that condition as a bit more restricted that the reason suggests, if that’s the case.
(Side note, this can do probably something funny if findlib.conf’s path is using pattern characters but, oh, well)

shym · 2026-07-22T13:51:43Z

+                ocaml_config_from_stdlib="$(echo "$d3" | sed -e 's|[^/]*[^/]|..|g')"
+                ocaml_config_from_stdlib="${ocaml_config_from_stdlib##/}"
+                ocaml_sitelib_from_stdlib="$ocaml_config_from_stdlib"


Suggested change

ocaml_config_from_stdlib="$(echo "$d3" | sed -e 's|[^/]*[^/]|..|g')"

ocaml_config_from_stdlib="${ocaml_config_from_stdlib##/}"

ocaml_sitelib_from_stdlib="$ocaml_config_from_stdlib"

ocaml_sitelib_from_stdlib="$(echo "$d3" | sed -e 's|[^/]*[^/]|..|g')"

ocaml_sitelib_from_stdlib="${ocaml_sitelib_from_stdlib#/}"

I suggest to get rid of the temporary new var ocaml_sitelib_from_stdlib and to use the shortest prefix removal: when it’s a fixed-length string, I find it a bit weird to ask for the longest one.

shym · 2026-07-22T13:51:43Z

+                    ocaml_sitelib_from_stdlib="${ocaml_sitelib_from_stdlib}${dir_sep}${ocamlfind_conf_destdir}"
+                fi
+                # d3 should be of the form "/.../.../...". Convert all the
+                # characters between slashes to Filaname.dirname and then remove


Suggested change

# characters between slashes to Filaname.dirname and then remove

# characters between slashes to Filename.dirname and then remove

shym · 2026-07-22T13:51:43Z

+                # d3 should be of the form "/.../.../...". Convert all the
+                # characters between slashes to Filaname.dirname and then remove
+                # the slashes. macOS sed doesn't support EREs.
+                ocamlfind_conf_from_stdlib="fun p -> $(echo "$d3" | sed -e 's|[^/]*[^/]|Filename.dirname (|g;s|/||g')p$(echo "$d3" | sed -e 's|[^/]*[^/]|)|g;s|/||g')"


Suggested change

ocamlfind_conf_from_stdlib="fun p -> $(echo "$d3" | sed -e 's|[^/]*[^/]|Filename.dirname (|g;s|/||g')p$(echo "$d3" | sed -e 's|[^/]*[^/]|)|g;s|/||g')"

ocamlfind_conf_from_stdlib="fun p -> $(echo "$d3" | sed -e 's|//*[^/]*[^/]|Filename.dirname (|g')p$(echo "$d3" | sed -e 's|//*[^/]*[^/]|)|g')"

One s is enough, isn’t it?

shym · 2026-07-22T13:51:43Z

 	        $(SH) $(TOP)/tools/patch '@RELATIVE_PATHS@' '$(RELATIVE_PATHS)' | \
 		sed -e 's;@AUTOLINK@;$(OCAML_AUTOLINK);g' \
 		    -e 's;@SYSTEM@;$(SYSTEM);g' \
+	      -e 's;@CONFIG_FROM_STDLIB@;$(CONFIG_FROM_STDLIB);g' \


Suggested change

-e 's;@CONFIG_FROM_STDLIB@;$(CONFIG_FROM_STDLIB);g' \

-e 's;@CONFIG_FROM_STDLIB@;$(CONFIG_FROM_STDLIB);g' \

to fix alignment

shym · 2026-07-22T13:51:43Z

+            let rec split acc dir =
+              let dirname = Filename.dirname dir in
+              let basename = Filename.basename dir in
+              if dirname = Filename.current_dir_name then
+                List.fold_left Filename.concat "" (basename :: acc)
+              else
+                split (Filename.basename dir :: acc) dirname in


Does split do more than trimming an initial ./ (in a portable way)? (ie, it might be worth a comment to explain it, and maybe rename it trim_dotslash, as the result is re-concatenated)
(And I wondered about a non-recursive function then, even if the depth is probably quite limited, and I understand this is annoying to cover the case of a .// prefix but this annoying case could be just ignored I’d say)

shym · 2026-07-22T13:51:43Z

+           since OCaml 5.4. The interpretation of non-absolute lines in ld.conf
+           prior to OCaml 5.4 was not useful, so this behaviour is done without


This should be 5.5, shouldn’t it? Or rephrased a bit to only talk about Relocatable OCaml.
(This also appears in 739d3dc and 1bcb370 messages)

shym · 2026-07-22T13:51:44Z

+(** Entries in ld.conf *)
+type ldconf_entry = {
+  raw: string; (** Raw entry line *)
+  eff: string  (** Evaluated entry line *)


Suggested change

eff: string (** Evaluated entry line *)

eff: string

(** Effective entry line with explicit-relative paths resolved to absolute

paths *)

shym · 2026-07-22T13:51:44Z

+        run: |
+          first="$(opam var bin | tr -d '\r')/ocamlfind${{ runner.os == 'Windows' && '.exe' || '' }}"
+          second="$(opam var --switch=second bin | tr -d '\r')/ocamlfind${{ runner.os == 'Windows' && '.exe' || '' }}"


Suggested change

run: |

first="$(opam var bin | tr -d '\r')/ocamlfind${{ runner.os == 'Windows' && '.exe' || '' }}"

second="$(opam var --switch=second bin | tr -d '\r')/ocamlfind${{ runner.os == 'Windows' && '.exe' || '' }}"

env:

EXE: ${{ runner.os == 'Windows' && '.exe' || '' }}

run: |

first="$(opam var bin | tr -d '\r')/ocamlfind$EXE"

second="$(opam var --switch=second bin | tr -d '\r')/ocamlfind$EXE"

maybe, if only to shorten lines?

rlepigre-skylabs-ai · 2026-08-06T19:46:00Z

@dra27 Is there anything I can do to help get this merged, and then released?

dra27 linked an issue Jul 17, 2026 that may be closed by this pull request

ocamlfind warning "Cannot read directory ../stublibs which is mentioned in ld.conf" #115

Open

This was referenced Jul 17, 2026

Remove -with-relative-paths-at support #123

Draft

Make paths from ld.conf absolute #119

Closed

Windows build fixes (MSYS2, Cygwin, etc.) #121

Open

dra27 force-pushed the win-fixes branch from eba0ac6 to 159460f Compare July 18, 2026 06:24

dra27 added 7 commits July 18, 2026 07:24

Restore selection mechanism for topfind generation

1bb163a

Build relocatably

7db3735

Temporarily disable the sandbox on macOS

1faecd4

Works around cloning problems in OCaml 5.5

dra27 force-pushed the relocatable branch from dabe21e to 1faecd4 Compare July 18, 2026 06:25

dra27 mentioned this pull request Jul 18, 2026

Add an OCaml 5.5-compatible ocamlfind preview package ocaml/opam-repository#30285

Merged

shym approved these changes Jul 22, 2026

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Relocatable ocamlfind with sprinkles - #122

Relocatable ocamlfind with sprinkles#122
dra27 wants to merge 7 commits into
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	# Standard Library directory. For normal Findlib, equal to
	# Standard Library directory. For non-relocatable Findlib, equal to

		elif [ "x$d1" = "x${d1#$d2}" ] \|\| [ "x$d3" = "x{$d3##/}" ]; then
		non_relocatable_reason="findlib.conf and the Standard Library don't share a common path"

	# characters between slashes to Filaname.dirname and then remove
	# characters between slashes to Filename.dirname and then remove

	ocamlfind_conf_from_stdlib="fun p -> $(echo "$d3" \| sed -e 's\|[^/][^/]\|Filename.dirname (\|g;s\|/\|\|g')p$(echo "$d3" \| sed -e 's\|[^/][^/]\|)\|g;s\|/\|\|g')"
	ocamlfind_conf_from_stdlib="fun p -> $(echo "$d3" \| sed -e 's\|//[^/][^/]\|Filename.dirname (\|g')p$(echo "$d3" \| sed -e 's\|//[^/][^/]\|)\|g')"

	-e 's;@CONFIG_FROM_STDLIB@;$(CONFIG_FROM_STDLIB);g' \
	-e 's;@CONFIG_FROM_STDLIB@;$(CONFIG_FROM_STDLIB);g' \

		since OCaml 5.4. The interpretation of non-absolute lines in ld.conf
		prior to OCaml 5.4 was not useful, so this behaviour is done without

-        run: |
-          first="$(opam var bin | tr -d '\r')/ocamlfind${{ runner.os == 'Windows' && '.exe' || '' }}"
-          second="$(opam var --switch=second bin | tr -d '\r')/ocamlfind${{ runner.os == 'Windows' && '.exe' || '' }}"
+        env:
+          EXE: ${{ runner.os == 'Windows' && '.exe' || '' }}
+        run: |
+          first="$(opam var bin | tr -d '\r')/ocamlfind$EXE"
+          second="$(opam var --switch=second bin | tr -d '\r')/ocamlfind$EXE"

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