From b77e947f37d34751aee230ea26185bff33823836 Mon Sep 17 00:00:00 2001
From: David Allsopp <david.allsopp@metastack.com>
Date: Thu, 11 Sep 2025 11:16:52 +0100
Subject: [PATCH] Be more liberal with Sys.ocaml_version

--compiler-version continues to require an explicitly recognised
version, but allow the build to proceed with unknown compiler versions.
In particular, the list then doesn't need updating on any point release
of existing compiler, and stdcompat can be pinned with a development of
OCaml up to the point where a new function is added.
---
 tools/compiler_version.ml  |  6 +++++-
 tools/compiler_version.mli |  2 ++
 tools/stdcompatpp.mll      | 23 +++++++++++++++--------
 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/tools/compiler_version.ml b/tools/compiler_version.ml
index f675a20..ee4169b 100644
--- a/tools/compiler_version.ml
+++ b/tools/compiler_version.ml
@@ -137,11 +137,15 @@ let known_versions =
 
 let is_known v = List.mem v known_versions
 
+let is_known_release {major; minor; _} =
+  List.exists (fun { major = major'; minor = minor'; _ } ->
+    major = major' && minor = minor') known_versions
+
 let is_development _ = false
 
 let make x y z extra_info =
   let v = mk x y z in
-  if is_known v then { v with extra_info } else raise Not_found
+  { v with extra_info }
 
 let to_string { major; minor; patch_level; extra_info } =
   let printer = Printf.sprintf in
diff --git a/tools/compiler_version.mli b/tools/compiler_version.mli
index c3ab3d6..7c272fd 100644
--- a/tools/compiler_version.mli
+++ b/tools/compiler_version.mli
@@ -56,6 +56,8 @@ val known_versions : t list
 
 val is_known : t -> bool
 
+val is_known_release : t -> bool
+
 val is_development : t -> bool
 
 val major : t -> int
diff --git a/tools/stdcompatpp.mll b/tools/stdcompatpp.mll
index 57914b1..9b49a2b 100644
--- a/tools/stdcompatpp.mll
+++ b/tools/stdcompatpp.mll
@@ -27,8 +27,8 @@ type options = {
   debug : bool;
 }
 
-let init_options () = {
-  compiler_version = Compiler_version.of_string Sys.ocaml_version;
+let init_options compiler_version = {
+  compiler_version;
   source_type = OCaml;
   debug = false;
 }
@@ -40,11 +40,11 @@ let dprintf options fmt =
   printer stderr fmt
 
 let set_compiler_version opts version =
-  let compiler_version =
-    try Compiler_version.of_string version with
-    _ -> unknown "compiler version" version
-  in
-  opts := { !opts with compiler_version  }
+  let compiler_version = Compiler_version.of_string version in
+  if Compiler_version.is_known compiler_version then
+    opts := { !opts with compiler_version  }
+  else
+    unknown "compiler version" version
 
 let set_source_type opts source_type =
   let source_type =
@@ -339,7 +339,14 @@ and c_lexer options state = parse
 {
 
 let main () =
-  let options = init_options () |> parse_commandline in
+  let compiler_version = Compiler_version.of_string Sys.ocaml_version in
+  let compiler_version =
+    if Compiler_version.is_known_release compiler_version then
+      compiler_version
+    else
+      List.hd (List.rev Compiler_version.known_versions)
+  in
+  let options = init_options compiler_version |> parse_commandline in
   let lexer = match options.source_type with
     | OCaml -> ocaml_lexer
     | C -> c_lexer