Export major version of latest Emacs supported by emacs-module.h.

This is useful if module authors want to support multiple versions of
emacs-module.h.

* configure.ac (emacs_major_version): Define substitution.

* src/emacs-module.h.in (EMACS_MAJOR_VERSION): Define macro.

* doc/lispref/internals.texi (Module Initialization): Document
EMACS_MAJOR_VERSION preprocessor macro.

* test/data/emacs-module/mod-test.c (emacs_module_init): Verify
behavior of EMACS_MAJOR_VERSION.

1 files changed, 3 insertions, 0 deletions

diff --git a/etc/NEWS b/etc/NEWS
index cf6f4fea3e9..9b32d720b62 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1933,6 +1933,9 @@ convert between timespec structures and Emacs Lisp time values.
 'extract_big_integer' to create and extract arbitrary-size integer
 values.
 
+** emacs-module.h now defines a macro EMACS_MAJOR_VERSION that expands
+to the major version of the latest Emacs supported by the header.
+
 
 * Changes in Emacs 27.1 on Non-Free Operating Systems