Free out safe arrays after conversion (#2557)

Author: the-snork

.github/workflows/main.yml

@@ -157,8 +157,7 @@ jobs:
         with:
           version: "0.8.4"
       - run: ruff format --check
-      - run:
-          | # Too many files to fit in a single command, also exclude vendored Scintilla and MAPIStubLibrary
+      - run: | # Too many files to fit in a single command, also exclude vendored Scintilla and MAPIStubLibrary
           clang-format --Werror --dry-run $(git ls-files '*.cpp' ':!:com/win32comext/mapi/src/MAPIStubLibrary/')
           if ($LastExitCode -ne 0) { exit $LastExitCode }
           clang-format --Werror --dry-run $(git ls-files '*.h' ':!:Pythonwin/Scintilla/' ':!:com/win32comext/mapi/src/MAPIStubLibrary/')

CHANGES.txt

@@ -14,6 +14,7 @@ https://mhammond.github.io/pywin32_installers.html .
 Coming in build 311, as yet unreleased
 --------------------------------------
 * Fixed a regression that broke special __dunder__ methods with CoClass. (#1870, #2493, @Avasam, @geppi)
+* Fixed a memory leak when SafeArrays are used as out parameters (@the-snork)
 * Fixed dispatch handling for properties (@the-snork)
 
 Build 310, released 2025/03/16

com/TestSources/PyCOMTest/PyCOMImpl.cpp

@@ -379,6 +379,13 @@ STDMETHODIMP CPyCOMTest::GetSafeArrays(SAFEARRAY **attrs, SAFEARRAY **attrs2, SA
     return S_OK;
 }
 
+STDMETHODIMP CPyCOMTest::GetByteArray(long sizeBytes, SAFEARRAY **array)
+{
+    SAFEARRAYBOUND bound = {static_cast<ULONG>(sizeBytes), 0};
+    *array = SafeArrayCreate(VT_UI1, 1, &bound);
+    return S_OK;
+}
+
 STDMETHODIMP CPyCOMTest::GetSimpleSafeArray(SAFEARRAY **attrs) { return MakeFillIntArray(attrs, 10, VT_I4); }
 
 STDMETHODIMP CPyCOMTest::CheckVariantSafeArray(SAFEARRAY **attrs, int *result)

com/TestSources/PyCOMTest/PyCOMImpl.h

@@ -80,6 +80,7 @@ class CPyCOMTest : public IDispatchImpl<IPyCOMTest, &IID_IPyCOMTest, &LIBID_PyCO
     STDMETHOD(SetDoubleSafeArray)(SAFEARRAY *vars, int *retSize);
     STDMETHOD(SetFloatSafeArray)(SAFEARRAY *vars, int *retSize);
     STDMETHOD(GetSafeArrays)(SAFEARRAY **attrs, SAFEARRAY **attrs2, SAFEARRAY **ints);
+    STDMETHOD(GetByteArray)(long sizeBytes, SAFEARRAY **array);
     STDMETHOD(GetSimpleSafeArray)(SAFEARRAY **ints);
     STDMETHOD(ChangeDoubleSafeArray)(SAFEARRAY **vals);
     STDMETHOD(GetSimpleCounter)(ISimpleCounter **counter);

com/TestSources/PyCOMTest/PyCOMTest.idl

@@ -235,6 +235,7 @@ library PyCOMTestLib
 		HRESULT GetSafeArrays([out] SAFEARRAY(QsAttribute)* attrs,
                                       [out] SAFEARRAY(enum tagQsAttribute)*attrs2,
                                       [out] SAFEARRAY(int)*ints);
+        HRESULT GetByteArray([in] long sizeInBytes, [out] SAFEARRAY(byte) *bytes);
 		HRESULT ChangeDoubleSafeArray([in, out]SAFEARRAY(double)*vals);
 		HRESULT GetSimpleCounter([out, retval] ISimpleCounter** counter);
 		HRESULT CheckVariantSafeArray([in] SAFEARRAY(VARIANT)* data, [out, retval]int *sum);

com/TestSources/PyCOMTest/PyCOMTest.vcxproj

@@ -161,4 +161,4 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
-</Project>
+</Project>

com/win32com/src/PyIDispatch.cpp

@@ -517,7 +517,12 @@ PyObject *PyIDispatch::InvokeTypes(PyObject *self, PyObject *args)
 
 error:
     if (dispparams.rgvarg) {
-        for (i = dispparams.cArgs; i--;) VariantClear(&dispparams.rgvarg[i]);
+        for (i = dispparams.cArgs; i--;) {
+            if ((V_VT(&dispparams.rgvarg[i]) & ~VT_TYPEMASK) == (VT_BYREF | VT_ARRAY)) {
+                SafeArrayDestroy(*V_ARRAYREF(&dispparams.rgvarg[i]));
+            }
+            VariantClear(&dispparams.rgvarg[i]);
+        }
         delete[] dispparams.rgvarg;
     }
     delete[] ArgHelpers;

com/win32com/test/testPyComTest.py

@@ -16,6 +16,7 @@
 import win32com.test.util
 import win32timezone
 import winerror
+from win32api import CloseHandle, GetCurrentProcessId, OpenProcess
 from win32com.client import (
     VARIANT,
     CastTo,
@@ -24,6 +25,7 @@
     constants,
     register_record_class,
 )
+from win32process import GetProcessMemoryInfo
 
 importMsg = "**** PyCOMTest is not installed ***\n  PyCOMTest is a Python test specific COM client and server.\n  It is likely this server is not installed on this machine\n  To install the server, you must get the win32com sources\n  and build it using MS Visual C++"
 
@@ -137,6 +139,16 @@ def TestConstant(constName, pyConst):
     ), f"Constant value wrong for {constName} - got {comConst}, wanted {pyConst}"
 
 
+def GetMemoryUsage():
+    pid = GetCurrentProcessId()
+    PROCESS_QUERY_INFORMATION = 0x0400
+    PROCESS_VM_READ = 0x0010
+    hprocess = OpenProcess(PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, False, pid)
+    mem_info = GetProcessMemoryInfo(hprocess)
+    CloseHandle(hprocess)
+    return mem_info["WorkingSetSize"]
+
+
 # Simple handler class.  This demo only fires one event.
 class RandomEventHandler:
     def _Init(self):
@@ -601,6 +613,13 @@ def TestGenerated():
     TestApplyResult(o.SetLongLongSafeArray, (ll,), len(ll))
     TestApplyResult(o.SetULongLongSafeArray, (ll,), len(ll))
 
+    # check freeing of safe arrays
+    mem_before = GetMemoryUsage()
+    o.GetByteArray(50 * 1024 * 1024)
+    mem_after = GetMemoryUsage()
+    delta = mem_after - mem_before
+    assert delta < 1024 * 1024, f"Memory not freed - delta {delta / (1024 * 1024)} MB"
+
     # Tell the server to do what it does!
     TestApplyResult(o.Test2, (constants.Attr2,), constants.Attr2)
     TestApplyResult(o.Test3, (constants.Attr2,), constants.Attr2)