Merge PR #9605: [coq_makefile] Enforce warn_error for plugins.

Reviewed-by: SkySkimmer
Ack-by: Zimmi48
Reviewed-by: gares

9 files changed, 40 insertions, 5 deletions

diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 3c427793e2..b074427892 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -662,5 +662,5 @@ plugin:plugin-tutorial:
 plugin:ci-quickchick:
   extends: .ci-template-flambda
 
-plugin:ci-relation-algebra:
+plugin:ci-relation_algebra:
   extends: .ci-template
diff --git a/Makefile.ci b/Makefile.ci
index 000725b6b1..a244c17ef3 100644
--- a/Makefile.ci
+++ b/Makefile.ci
@@ -38,7 +38,7 @@ CI_TARGETS= \
     ci-mtac2 \
     ci-paramcoq \
     ci-quickchick \
-    ci-relation-algebra \
+    ci-relation_algebra \
     ci-sf \
     ci-simple-io \
     ci-stdlib2 \
diff --git a/dev/ci/README-users.md b/dev/ci/README-users.md
index 01769aeddb..06b617d4c1 100644
--- a/dev/ci/README-users.md
+++ b/dev/ci/README-users.md
@@ -45,6 +45,26 @@ using [coqbot](https://github.com/coq/bot); meanwhile, a workaround is
 to give merge permissions to someone from the Coq team as to help with
 these kind of merges.
 
+### OCaml and plugin-specific considerations
+
+Developments that link against Coq's OCaml API [most of them are known
+as "plugins"] do have some special requirements:
+
+- Coq's OCaml API is not stable. We hope to improve this in the future
+  but as of today you should expect to have to merge a fair amount of
+  "overlays", usually in the form of Pull Requests from Coq developers
+  in order to keep your plugin compatible with Coq master.
+
+  In order to alleviate the load, you can delegate the merging of such
+  compatibility pull requests to Coq developers themselves, by
+  granting access to the plugin repository or by using `bots` such as
+  [Bors](https://github.com/apps/bors) that allow for automatic
+  management of Pull Requests.
+
+- Plugins in the CI should compile with the OCaml flags that Coq
+  uses. In particular, warnings that are considered fatal by the Coq
+  developers _must_ be also fatal for plugin CI code.
+
 ### Add your development by submitting a pull request
 
 Add a new `ci-mydev.sh` script to [`dev/ci`](.); set the corresponding
diff --git a/dev/ci/ci-basic-overlay.sh b/dev/ci/ci-basic-overlay.sh
index 0c89809ee9..4f5988c59c 100755
--- a/dev/ci/ci-basic-overlay.sh
+++ b/dev/ci/ci-basic-overlay.sh
@@ -254,7 +254,7 @@
 : "${paramcoq_CI_ARCHIVEURL:=${paramcoq_CI_GITURL}/archive}"
 
 ########################################################################
-# relation-algebra
+# relation_algebra
 ########################################################################
 : "${relation_algebra_CI_REF:=master}"
 : "${relation_algebra_CI_GITURL:=https://github.com/damien-pous/relation-algebra}"
diff --git a/dev/ci/ci-relation-algebra.sh b/dev/ci/ci-relation_algebra.sh
index 84bed5bdfe..84bed5bdfe 100755
--- a/dev/ci/ci-relation-algebra.sh
+++ b/dev/ci/ci-relation_algebra.sh
diff --git a/dev/doc/changes.md b/dev/doc/changes.md
index 40c3c32e4f..4533a4dc01 100644
--- a/dev/doc/changes.md
+++ b/dev/doc/changes.md
@@ -20,6 +20,15 @@ General deprecation
   removed. Please, make sure your plugin is warning-free in 8.8 before
   trying to port it over 8.9.
 
+Warnings
+
+- Coq now builds plugins with `-warn-error` enabled by default. The
+  amount of dangerous warnings in plugin code was very high, so we now
+  require plugins in the CI to adhere to the Coq warning policy. We
+  _strongly_ recommend against disabling the default set of warnings.
+  If you have special needs, see the documentation of your build
+  system and/or OCaml for further help.
+
 Names
 
 - Kernel names no longer contain a section path. They now have only two
diff --git a/doc/sphinx/practical-tools/utilities.rst b/doc/sphinx/practical-tools/utilities.rst
index 8346b72cb9..35231610fe 100644
--- a/doc/sphinx/practical-tools/utilities.rst
+++ b/doc/sphinx/practical-tools/utilities.rst
@@ -144,6 +144,10 @@ Here we describe only few of them.
 :CAMLFLAGS:
    can be used to specify additional flags to the |OCaml|
    compiler, like ``-bin-annot`` or ``-w``....
+:OCAMLWARN:
+   it contains a default of ``-warn-error +a-3``, useful to modify
+   this setting; beware this is not recommended for projects in
+   Coq's CI.
 :COQC, COQDEP, COQDOC:
    can be set in order to use alternative binaries
    (e.g. wrappers)
diff --git a/lib/envars.ml b/lib/envars.ml
index 0f4670688b..af8e45b137 100644
--- a/lib/envars.ml
+++ b/lib/envars.ml
@@ -178,6 +178,7 @@ let print_config ?(prefix_var_name="") f coq_src_subdirs =
   fprintf f "%sDOCDIR=%s/\n" prefix_var_name (docdir ());
   fprintf f "%sOCAMLFIND=%s\n" prefix_var_name (ocamlfind ());
   fprintf f "%sCAMLFLAGS=%s\n" prefix_var_name Coq_config.caml_flags;
+  fprintf f "%sWARN=%s\n" prefix_var_name "-warn-error +a-3";
   fprintf f "%sHASNATDYNLINK=%s\n" prefix_var_name
     (if Coq_config.has_natdynlink then "true" else "false");
   fprintf f "%sCOQ_SRC_SUBDIRS=%s\n" prefix_var_name (String.concat " " coq_src_subdirs)
diff --git a/tools/CoqMakefile.in b/tools/CoqMakefile.in
index 51e0300182..2ec55d1bd0 100644
--- a/tools/CoqMakefile.in
+++ b/tools/CoqMakefile.in
@@ -38,6 +38,7 @@ DOCDIR            := $(COQMF_DOCDIR)
 OCAMLFIND         := $(COQMF_OCAMLFIND)
 CAMLFLAGS         := $(COQMF_CAMLFLAGS)
 HASNATDYNLINK     := $(COQMF_HASNATDYNLINK)
+OCAMLWARN         := $(COQMF_WARN)
 
 @CONF_FILE@: @PROJECT_FILE@
 	@COQ_MAKEFILE_INVOCATION@
@@ -190,9 +191,9 @@ COQMAKEFILE_VERSION:=@COQ_VERSION@
 COQSRCLIBS?= $(foreach d,$(COQ_SRC_SUBDIRS), -I "$(COQLIB)/$(d)")
 
 CAMLFLAGS+=$(OCAMLLIBS) $(COQSRCLIBS)
-
 # ocamldoc fails with unknown argument otherwise
-CAMLDOCFLAGS=$(filter-out -annot, $(filter-out -bin-annot, $(CAMLFLAGS)))
+CAMLDOCFLAGS:=$(filter-out -annot, $(filter-out -bin-annot, $(CAMLFLAGS)))
+CAMLFLAGS+=$(OCAMLWARN)
 
 ifneq (,$(TIMING))
 TIMING_ARG=-time