fix build with boehm-gc 7.4.0+ (patch by Vladimir Smirnov, slightly modified by me)

Fixed bugs:
  - https://launchpad.net/bugs/1265072

(bzr r12918)

2 files changed, 14 insertions, 6 deletions

diff --git a/src/gc-core.h b/src/gc-core.h
index 85fbada60..3957bda1a 100644
--- a/src/gc-core.h
+++ b/src/gc-core.h
@@ -57,7 +57,7 @@ struct Ops {
                                            CleanupFunc *old_func,
                                            void **old_data);
     int (*general_register_disappearing_link)(void **p_ptr,
-                                              void *base);
+                                              void const *base);
     int (*unregister_disappearing_link)(void **p_ptr);
     std::size_t (*get_heap_size)();
     std::size_t (*get_free_bytes)();
diff --git a/src/gc.cpp b/src/gc.cpp
index 9c59691cb..280a8b1dc 100644
--- a/src/gc.cpp
+++ b/src/gc.cpp
@@ -70,9 +70,13 @@ void *debug_base(void *ptr) {
     return base + debug_base_fixup();
 }
 
-int debug_general_register_disappearing_link(void **p_ptr, void *base) {
-    char *real_base=reinterpret_cast<char *>(base) - debug_base_fixup();
+int debug_general_register_disappearing_link(void **p_ptr, void const *base) {
+    char const *real_base = reinterpret_cast<char const *>(base) - debug_base_fixup();
+#if (GC_MAJOR_VERSION >= 7 && GC_MINOR_VERSION >= 4)
     return GC_general_register_disappearing_link(p_ptr, real_base);
+#else // compatibility with older Boehm GC versions
+    return GC_general_register_disappearing_link(p_ptr, const_cast<char *>(real_base));
+#endif
 }
 
 void dummy_do_init() {}
@@ -90,7 +94,7 @@ void dummy_register_finalizer(void *, CleanupFunc, void *,
     }
 }
 
-int dummy_general_register_disappearing_link(void **, void *) { return false; }
+int dummy_general_register_disappearing_link(void **, void const *) { return false; }
 
 int dummy_unregister_disappearing_link(void **/*link*/) { return false; }
 
@@ -112,7 +116,11 @@ Ops enabled_ops = {
     &GC_malloc_atomic_uncollectable,
     &GC_base,
     &GC_register_finalizer_ignore_self,
-    &GC_general_register_disappearing_link,
+#if (GC_MAJOR_VERSION >= 7 && GC_MINOR_VERSION >= 4)
+     &GC_general_register_disappearing_link,
+#else // compatibility with older Boehm GC versions
+    (int (*)(void**, const void*))(&GC_general_register_disappearing_link),
+#endif
     &GC_unregister_disappearing_link,
     &GC_get_heap_size,
     &GC_get_free_bytes,
@@ -202,7 +210,7 @@ void stub_register_finalizer_ignore_self(void *, CleanupFunc, void *,
     die_because_not_initialized();
 }
 
-int stub_general_register_disappearing_link(void **, void *) {
+int stub_general_register_disappearing_link(void **, void const *) {
     die_because_not_initialized();
     return 0;
 }