Merge pull request #20124 from JuliaLang/sb/libgit2/refcount

Add reference count to LibGit2 objects
JuliaLang · Jan 21, 2017 · d3bac6e · d3bac6e
2 parents fc4dc29 + 20e24bc
commit d3bac6e
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Showing 2 changed files with 18 additions and 1 deletion.
diff --git a/base/libgit2/libgit2.jl b/base/libgit2/libgit2.jl
@@ -9,6 +9,8 @@ export with, GitRepo, GitConfig
 const GITHUB_REGEX =
     r"^(?:git@|git://|https://(?:[\w\.\+\-]+@)?)github.com[:/](([^/].+)/(.+?))(?:\.git)?$"i
 
+const REFCOUNT = Threads.Atomic{UInt}()
+
 include("utils.jl")
 include("consts.jl")
 include("types.jl")
@@ -612,8 +614,13 @@ function __init__()
 
     err = ccall((:git_libgit2_init, :libgit2), Cint, ())
     err > 0 || throw(ErrorException("error initializing LibGit2 module"))
+    REFCOUNT[] = 1
+
     atexit() do
-        ccall((:git_libgit2_shutdown, :libgit2), Cint, ())
+        if Threads.atomic_sub!(REFCOUNT, UInt(1)) == 1
+            # refcount zero, no objects to be finalized
+            ccall((:git_libgit2_shutdown, :libgit2), Cint, ())
+        end
     end
 
     @static if is_linux()

diff --git a/base/libgit2/types.jl b/base/libgit2/types.jl
@@ -449,9 +449,12 @@ for (typ, reporef, sup, cname) in [
         @eval type $typ <: $sup
             ptr::Ptr{Void}
             function $typ(ptr::Ptr{Void},fin=true)
+                # fin=false should only be used when the pointer should not be free'd
+                # e.g. from within callback functions which are passed a pointer
                 @assert ptr != C_NULL
                 obj = new(ptr)
                 if fin
+                    Threads.atomic_add!(REFCOUNT, UInt(1))
                     finalizer(obj, Base.close)
                 end
                 return obj
@@ -464,12 +467,14 @@ for (typ, reporef, sup, cname) in [
             function $typ(repo::GitRepo, ptr::Ptr{Void})
                 @assert ptr != C_NULL
                 obj = new(Nullable(repo), ptr)
+                Threads.atomic_add!(REFCOUNT, UInt(1))
                 finalizer(obj, Base.close)
                 return obj
             end
             function $typ(ptr::Ptr{Void})
                 @assert ptr != C_NULL
                 obj = new(Nullable{GitRepo}(), ptr)
+                Threads.atomic_add!(REFCOUNT, UInt(1))
                 finalizer(obj, Base.close)
                 return obj
             end
@@ -481,6 +486,7 @@ for (typ, reporef, sup, cname) in [
             function $typ(repo::GitRepo, ptr::Ptr{Void})
                 @assert ptr != C_NULL
                 obj = new(repo, ptr)
+                Threads.atomic_add!(REFCOUNT, UInt(1))
                 finalizer(obj, Base.close)
                 return obj
             end
@@ -490,6 +496,10 @@ for (typ, reporef, sup, cname) in [
         if obj.ptr != C_NULL
             ccall(($(string(cname, :_free)), :libgit2), Void, (Ptr{Void},), obj.ptr)
             obj.ptr = C_NULL
+            if Threads.atomic_sub!(REFCOUNT, UInt(1)) == 1
+                # will the last finalizer please turn out the lights?
+                ccall((:git_libgit2_shutdown, :libgit2), Cint, ())
+            end
         end
     end
 end