From eb89e50cbb4584bb42a425089640b2931b723cca Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Tue, 23 Jul 2024 16:21:43 +0200
Subject: [PATCH 1/2] Rejiggle getGCCycles() for buildNoGc

---
 src/libexpr/eval-gc.cc | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/libexpr/eval-gc.cc b/src/libexpr/eval-gc.cc
index 97b24e3fb..73ab809e5 100644
--- a/src/libexpr/eval-gc.cc
+++ b/src/libexpr/eval-gc.cc
@@ -206,10 +206,17 @@ static inline void initGCReal()
     }
 }
 
+static size_t gcCyclesAfterInit = 0;
+
+size_t getGCCycles()
+{
+    assertGCInitialized();
+    return static_cast<size_t>(GC_get_gc_no()) - gcCyclesAfterInit;
+}
+
 #endif
 
 static bool gcInitialised = false;
-static GC_word gcCyclesAfterInit = 0;
 
 void initGC()
 {
@@ -218,10 +225,11 @@ void initGC()
 
 #if HAVE_BOEHMGC
     initGCReal();
+
+    gcCyclesAfterInit = GC_get_gc_no();
 #endif
 
     gcInitialised = true;
-    gcCyclesAfterInit = GC_get_gc_no();
 }
 
 void assertGCInitialized()
@@ -229,10 +237,4 @@ void assertGCInitialized()
     assert(gcInitialised);
 }
 
-size_t getGCCycles()
-{
-    assertGCInitialized();
-    return GC_get_gc_no() - gcCyclesAfterInit;
-}
-
 } // namespace nix

From 5d6bc484beab6ff822815b5b26745710d8c86305 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Tue, 23 Jul 2024 16:24:43 +0200
Subject: [PATCH 2/2] Hide getGCCycles when we have no GC

Alternatively, we could make it return 0, but we don't need it in
the first place because the caller exists conditionally too.
---
 src/libexpr/eval-gc.hh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/libexpr/eval-gc.hh b/src/libexpr/eval-gc.hh
index 76f019729..005175eb7 100644
--- a/src/libexpr/eval-gc.hh
+++ b/src/libexpr/eval-gc.hh
@@ -15,9 +15,11 @@ void initGC();
  */
 void assertGCInitialized();
 
+#ifdef HAVE_BOEHMGC
 /**
  * The number of GC cycles since initGC().
  */
 size_t getGCCycles();
+#endif
 
-}
+} // namespace nix