From 58d24a4cb630a6162d6f7d2a85e41949fdf2ad36 Mon Sep 17 00:00:00 2001
From: Yorick van Pelt <yorick@yorickvanpelt.nl>
Date: Wed, 1 Mar 2023 15:07:00 +0100
Subject: [PATCH] Always disable GC in a coroutine unless the patch is applied

---
 boehmgc-coroutine-sp-fallback.diff | 22 +++++++++++++++++++---
 src/libexpr/eval.cc                |  4 +++-
 src/libutil/serialise.cc           |  9 ++++-----
 src/libutil/serialise.hh           |  4 ++--
 4 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/boehmgc-coroutine-sp-fallback.diff b/boehmgc-coroutine-sp-fallback.diff
index 2826486fb..5066d8278 100644
--- a/boehmgc-coroutine-sp-fallback.diff
+++ b/boehmgc-coroutine-sp-fallback.diff
@@ -1,8 +1,8 @@
 diff --git a/darwin_stop_world.c b/darwin_stop_world.c
-index 3dbaa3fb..36a1d1f7 100644
+index 0468aaec..b348d869 100644
 --- a/darwin_stop_world.c
 +++ b/darwin_stop_world.c
-@@ -352,6 +352,7 @@ GC_INNER void GC_push_all_stacks(void)
+@@ -356,6 +356,7 @@ GC_INNER void GC_push_all_stacks(void)
    int nthreads = 0;
    word total_size = 0;
    mach_msg_type_number_t listcount = (mach_msg_type_number_t)THREAD_TABLE_SZ;
@@ -10,7 +10,7 @@ index 3dbaa3fb..36a1d1f7 100644
    if (!EXPECT(GC_thr_initialized, TRUE))
      GC_thr_init();
  
-@@ -407,6 +408,19 @@ GC_INNER void GC_push_all_stacks(void)
+@@ -411,6 +412,19 @@ GC_INNER void GC_push_all_stacks(void)
              GC_push_all_stack_sections(lo, hi, p->traced_stack_sect);
            }
            if (altstack_lo) {
@@ -30,6 +30,22 @@ index 3dbaa3fb..36a1d1f7 100644
              total_size += altstack_hi - altstack_lo;
              GC_push_all_stack(altstack_lo, altstack_hi);
            }
+diff --git a/include/gc.h b/include/gc.h
+index edab6c22..f2c61282 100644
+--- a/include/gc.h
++++ b/include/gc.h
+@@ -2172,6 +2172,11 @@ GC_API void GC_CALL GC_win32_free_heap(void);
+         (*GC_amiga_allocwrapper_do)(a,GC_malloc_atomic_ignore_off_page)
+ #endif /* _AMIGA && !GC_AMIGA_MAKINGLIB */
+ 
++#if !__APPLE__
++/* Patch doesn't work on apple */
++#define NIX_BOEHM_PATCH_VERSION 1
++#endif
++
+ #ifdef __cplusplus
+   } /* extern "C" */
+ #endif
 diff --git a/pthread_stop_world.c b/pthread_stop_world.c
 index b5d71e62..aed7b0bf 100644
 --- a/pthread_stop_world.c
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index e5e8d2b22..7dcd10d50 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -385,10 +385,12 @@ void initGC()
     StackAllocator::defaultAllocator = &boehmGCStackAllocator;
 
 
+#if NIX_BOEHM_PATCH_VERSION != 1
     /* Used to disable GC when entering coroutines on macOS */
-    create_disable_gc = []() -> std::shared_ptr<void> {
+    create_coro_gc_hook = []() -> std::shared_ptr<void> {
         return std::make_shared<BoehmDisableGC>();
     };
+#endif
 
     /* Set the initial heap size to something fairly big (25% of
        physical RAM, up to a maximum of 384 MiB) so that in most cases
diff --git a/src/libutil/serialise.cc b/src/libutil/serialise.cc
index 0bdeec0cd..6e53239f5 100644
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -186,18 +186,17 @@ static DefaultStackAllocator defaultAllocatorSingleton;
 StackAllocator *StackAllocator::defaultAllocator = &defaultAllocatorSingleton;
 
 
-std::shared_ptr<void> (*create_disable_gc)() = []() -> std::shared_ptr<void> {
+std::shared_ptr<void> (*create_coro_gc_hook)() = []() -> std::shared_ptr<void> {
     return {};
 };
 
 /* This class is used for entry and exit hooks on coroutines */
 class CoroutineContext {
-#if __APPLE__
-    /* Disable GC when entering the coroutine on macOS, since it doesn't find the main thread stack in this case.
+    /* Disable GC when entering the coroutine without the boehm patch,
+     * since it doesn't find the main thread stack in this case.
      * std::shared_ptr<void> performs type-erasure, so it will call the right
      * deleter. */
-    const std::shared_ptr<void> disable_gc = create_disable_gc();
-#endif
+    const std::shared_ptr<void> coro_gc_hook = create_coro_gc_hook();
 public:
     CoroutineContext() {};
     ~CoroutineContext() {};
diff --git a/src/libutil/serialise.hh b/src/libutil/serialise.hh
index b895db779..ba6dbf619 100644
--- a/src/libutil/serialise.hh
+++ b/src/libutil/serialise.hh
@@ -551,10 +551,10 @@ struct StackAllocator {
     static StackAllocator *defaultAllocator;
 };
 
-/* Disabling GC when entering a coroutine (on macos).
+/* Disabling GC when entering a coroutine (without the boehm patch).
    mutable to avoid boehm gc dependency in libutil.
  */
-extern std::shared_ptr<void> (*create_disable_gc)();
+extern std::shared_ptr<void> (*create_coro_gc_hook)();
 
 
 }