Merge pull request #34 from SCIP-Interfaces/rs/memleak

deal with memory leaks, by implementing finalizer and MPB's `freemodel!`

Author: rschwarz

src/mpb_interface.jl

@@ -18,7 +18,14 @@ numvar(m::SCIPMathProgModel) = _getNumVars(m)
 "The number of proper constraints, excluding those from lazy callbacks."
 numconstr(m::SCIPMathProgModel) = _getNumConss(m)
 
-freemodel!(m::SCIPMathProgModel) = error("Not implemented for SCIP.jl!")
+function freemodel!(m::SCIPMathProgModel)
+    if m.inner.ptr_model != C_NULL
+        # call finalizer directly
+        freescip(m.inner)
+    else
+        Base.warn_once("Tried to free already freed model, ignoring.")
+    end
+end
 
 # TODO: mapping for :SemiCont, :SemiInt
 const vartypemap = Dict{Symbol, Cint}(

src/types.jl

@@ -13,11 +13,21 @@ type SCIPModel
         # TODO: check return code (everywhere!)
         ccall((:CSIPcreateModel, libcsip), Cint, (Ptr{Ptr{Void}}, ), _arr)
         m = new(_arr[1], options)
-        # QUESTION: Why is _arr not garbage-collected?
+        @assert m.ptr_model != C_NULL
+
+        finalizer(m, freescip)
         return m
     end
 end
 
+function freescip(m::SCIPModel)
+    # avoid double free
+    if m.ptr_model != C_NULL
+        _freeModel(m)
+        m.ptr_model = C_NULL
+    end
+end
+
 # Linear Quadratic Model
 
 type SCIPLinearQuadraticModel <: AbstractLinearQuadraticModel

src/wrapper.jl

@@ -10,8 +10,8 @@ function _patchVersion()
     ccall((:CSIPpatchVersion, libcsip), Cint, ())
 end
 
-function _freeModel(model::SCIPMathProgModel)
-    ccall((:CSIPfreeModel, libcsip), Cint, (Ptr{Void}, ), model.inner.ptr_model)
+function _freeModel(inner::SCIPModel)
+    ccall((:CSIPfreeModel, libcsip), Cint, (Ptr{Void}, ), inner.ptr_model)
 end
 
 function _addVar(model::SCIPMathProgModel, lowerbound::Cdouble,