From 4c1c4f79a3286d76ec5f2e4746b89af009b55e46 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 4 Aug 2025 10:57:24 +0200
Subject: [PATCH] Move setting GC_THREADS into eval-gc.hh

---
 src/libexpr/eval-gc.cc                      | 2 --
 src/libexpr/include/nix/expr/eval-gc.hh     | 3 ++-
 src/libexpr/include/nix/expr/eval-inline.hh | 3 ---
 src/libexpr/meson.build                     | 2 --
 4 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/src/libexpr/eval-gc.cc b/src/libexpr/eval-gc.cc
index ce2bcae8a..b17336a90 100644
--- a/src/libexpr/eval-gc.cc
+++ b/src/libexpr/eval-gc.cc
@@ -15,8 +15,6 @@
 #    include <pthread_np.h>
 #  endif
 
-#  include <gc/gc.h>
-#  include <gc/gc_cpp.h>
 #  include <gc/gc_allocator.h>
 
 #  include <boost/coroutine2/coroutine.hpp>
diff --git a/src/libexpr/include/nix/expr/eval-gc.hh b/src/libexpr/include/nix/expr/eval-gc.hh
index 25144d40c..813c2920d 100644
--- a/src/libexpr/include/nix/expr/eval-gc.hh
+++ b/src/libexpr/include/nix/expr/eval-gc.hh
@@ -3,12 +3,13 @@
 
 #include <cstddef>
 
-// For `NIX_USE_BOEHMGC`, and if that's set, `GC_THREADS`
+// For `NIX_USE_BOEHMGC`
 #include "nix/expr/config.hh"
 
 #if NIX_USE_BOEHMGC
 
 #  define GC_INCLUDE_NEW
+#  define GC_THREADS 1
 
 #  include <gc/gc.h>
 #  include <gc/gc_cpp.h>
diff --git a/src/libexpr/include/nix/expr/eval-inline.hh b/src/libexpr/include/nix/expr/eval-inline.hh
index a1fd0ae4a..749e51537 100644
--- a/src/libexpr/include/nix/expr/eval-inline.hh
+++ b/src/libexpr/include/nix/expr/eval-inline.hh
@@ -6,9 +6,6 @@
 #include "nix/expr/eval-error.hh"
 #include "nix/expr/eval-settings.hh"
 
-// For `NIX_USE_BOEHMGC`, and if that's set, `GC_THREADS`
-#include "nix/expr/config.hh"
-
 namespace nix {
 
 /**
diff --git a/src/libexpr/meson.build b/src/libexpr/meson.build
index adf26008d..e1a12106d 100644
--- a/src/libexpr/meson.build
+++ b/src/libexpr/meson.build
@@ -61,8 +61,6 @@ if bdw_gc.found()
     define_value = cxx.has_function(funcspec).to_int()
     configdata_priv.set(define_name, define_value)
   endforeach
-  # Affects ABI, because it changes what bdw_gc itself does!
-  configdata_pub.set('GC_THREADS', 1)
 endif
 # Used in public header. Affects ABI!
 configdata_pub.set('NIX_USE_BOEHMGC', bdw_gc.found().to_int())