From 39f408f66a2e73545e732eaf310f37624e6561fe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mat=C4=9Bj=20Cepl?= <mcepl@cepl.eu>
Date: Wed, 21 Jan 2026 17:10:46 +0100
Subject: [PATCH] Allow overriding COMPILER with UNVERSIONED_COMPILER

Introduce UNVERSIONED_COMPILER variable in Makefile.pre.in to allow
overriding the COMPILER macro definition during the build of
Python/getcompiler.o.

This enables reproducible builds by providing a way to set a generic
compiler identification string (e.g., "[GCC]") instead of the default
versioned one.

The rule is made conditional on UNVERSIONED_COMPILER being defined.

References: https://discuss.python.org/t/unversioned-compiler-symbol-for-getcompiler-c/91735
Fixes: https://github.com/python/cpython/issues/144121
---
 Makefile.pre.in                                            | 7 +++++++
 .../Build/2026-01-21-19-28-11.gh-issue-144121.gaqpK-.rst   | 2 ++
 2 files changed, 9 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Build/2026-01-21-19-28-11.gh-issue-144121.gaqpK-.rst

diff --git a/Makefile.pre.in b/Makefile.pre.in
index 8531162943ae35..bf01f7ff4f835c 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -1926,6 +1926,13 @@ Modules/getbuildinfo.o: $(PARSER_OBJS) \
 	      -DGITBRANCH="\"`LC_ALL=C $(GITBRANCH)`\"" \
 	      -o $@ $(srcdir)/Modules/getbuildinfo.c
 
+ifdef UNVERSIONED_COMPILER
+Python/getcompiler.o: $(srcdir)/Python/getcompiler.c Makefile
+	$(CC) -c $(PY_CORE_CFLAGS) \
+		-DCOMPILER='"$(UNVERSIONED_COMPILER)"' \
+		-o $@ $(srcdir)/Python/getcompiler.c
+endif
+
 Modules/getpath.o: $(srcdir)/Modules/getpath.c Python/frozen_modules/getpath.h Makefile $(PYTHON_HEADERS)
 	$(CC) -c $(PY_CORE_CFLAGS) -DPYTHONPATH='"$(PYTHONPATH)"' \
 		-DPREFIX='"$(host_prefix)"' \
diff --git a/Misc/NEWS.d/next/Build/2026-01-21-19-28-11.gh-issue-144121.gaqpK-.rst b/Misc/NEWS.d/next/Build/2026-01-21-19-28-11.gh-issue-144121.gaqpK-.rst
new file mode 100644
index 00000000000000..d830d100b75d27
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2026-01-21-19-28-11.gh-issue-144121.gaqpK-.rst
@@ -0,0 +1,2 @@
+Make it possible for the COMPILER definition in getcompiler.c to be static
+in order to make builds reproducible.