Free temporary enums on failure (#50471)

* Free temporary enums on failure

* PR feedback

Author: tmds

src/coreclr/md/compiler/assemblymd.cpp

@@ -444,7 +444,7 @@ STDMETHODIMP RegMeta::EnumExportedTypes(           // S_OK or error
     BEGIN_ENTRYPOINT_NOTHROW;
 
     HENUMInternal       **ppmdEnum = reinterpret_cast<HENUMInternal **> (phEnum);
-    HENUMInternal       *pEnum;
+    HENUMInternal       *pEnum = NULL;
 
     LOG((LOGMD, "MD RegMeta::EnumExportedTypes(%#08x, %#08x, %#08x, %#08x)\n",
         phEnum, rExportedTypes, cMax, pcTokens));
@@ -488,14 +488,14 @@ STDMETHODIMP RegMeta::EnumExportedTypes(           // S_OK or error
 
         // set the output parameter.
         *ppmdEnum = pEnum;
+        pEnum = NULL;
     }
-    else
-        pEnum = *ppmdEnum;
 
     // we can only fill the minimum of what the caller asked for or what we have left.
-    IfFailGo(HENUMInternal::EnumWithCount(pEnum, cMax, rExportedTypes, pcTokens));
+    IfFailGo(HENUMInternal::EnumWithCount(*ppmdEnum, cMax, rExportedTypes, pcTokens));
 ErrExit:
     HENUMInternal::DestroyEnumIfEmpty(ppmdEnum);
+    HENUMInternal::DestroyEnum(pEnum);
 
     STOP_MD_PERF(EnumExportedTypes);
     END_ENTRYPOINT_NOTHROW;

src/coreclr/md/compiler/custattr_import.cpp

@@ -108,7 +108,7 @@ STDMETHODIMP RegMeta::EnumCustomAttributes(
     HENUMInternal   **ppmdEnum = reinterpret_cast<HENUMInternal **> (phEnum);
     RID             ridStart;
     RID             ridEnd;
-    HENUMInternal   *pEnum = *ppmdEnum;
+    HENUMInternal   *pEnum = NULL;
     CustomAttributeRec  *pRec;
     ULONG           index;
 
@@ -117,7 +117,7 @@ STDMETHODIMP RegMeta::EnumCustomAttributes(
     START_MD_PERF();
     LOCKREAD();
 
-    if ( pEnum == 0 )
+    if ( *ppmdEnum == 0 )
     {
         // instantiating a new ENUM
         CMiniMdRW       *pMiniMd = &(m_pStgdb->m_MiniMd);
@@ -220,13 +220,15 @@ STDMETHODIMP RegMeta::EnumCustomAttributes(
 
         // set the output parameter
         *ppmdEnum = pEnum;
+        pEnum = NULL;
     }
 
     // fill the output token buffer
-    hr = HENUMInternal::EnumWithCount(pEnum, cMax, rCustomAttributes, pcCustomAttributes);
+    hr = HENUMInternal::EnumWithCount(*ppmdEnum, cMax, rCustomAttributes, pcCustomAttributes);
 
 ErrExit:
     HENUMInternal::DestroyEnumIfEmpty(ppmdEnum);
+    HENUMInternal::DestroyEnum(pEnum);
 
     STOP_MD_PERF(EnumCustomAttributes);
     END_ENTRYPOINT_NOTHROW;