tdf#88442 SBasic: Don't double-initialize a Global ... As New ...

"As New" variables use lazy instantiation, but that should not re-apply each
time one re-enters the module. If the object is still there, don't replace it.

Change-Id: Ic568a56b93db9bc9139d434d97a4a4deb05840df
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/112018
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

3 files changed, 56 insertions, 6 deletions

diff --git a/basic/source/comp/dim.cxx b/basic/source/comp/dim.cxx
index 20396cd729ad..cf14d1c7818c 100644
--- a/basic/source/comp/dim.cxx
+++ b/basic/source/comp/dim.cxx
@@ -446,12 +446,39 @@ void SbiParser::DefVar( SbiOpcode eOp, bool bStatic )
             {
                 SbiExpression aExpr( this, *pDef );
                 aExpr.Gen();
+
+                /* tdf#88442
+                 * Don't initialize a
+                 *      Global X as New SomeObjectType
+                 * if it has already been initialized.
+                 * This approach relies on JUMPT evaluating Object->NULL as being 'false'
+                 * But the effect of this code is similar to inserting
+                 *  If IsNull(YourGlobal)
+                 *      Set YourGlobal = ' new obj
+                 *  End If ' If IsNull(YourGlobal)
+                 * Only for globals. For locals that check is skipped as it's unnecessary
+                 */
+                sal_uInt32 come_from = 0;
+                if ( pDef->GetScope() == SbGLOBAL )
+                {
+                    come_from = aGen.Gen( SbiOpcode::JUMPT_, 0 );
+                    aGen.Gen( SbiOpcode::FIND_, pDef->GetId(), pDef->GetTypeId() );
+                }
+
                 SbiOpcode eOp_ = pDef->IsNew() ? SbiOpcode::CREATE_ : SbiOpcode::TCREATE_;
                 aGen.Gen( eOp_, pDef->GetId(), pDef->GetTypeId() );
                 if ( bVBASupportOn )
                     aGen.Gen( SbiOpcode::VBASET_ );
                 else
                     aGen.Gen( SbiOpcode::SET_ );
+
+                if ( come_from )
+                {
+                    // See other tdf#88442 comment above where come_from is
+                        // initialized. This is effectively 'inserting' the
+                        // End If ' If IsNull(YourGlobal)
+                    aGen.BackChain( come_from );
+                }
             }
         }
         else
diff --git a/basic/source/inc/runtime.hxx b/basic/source/inc/runtime.hxx
index 1169820e753b..73e56838e2aa 100644
--- a/basic/source/inc/runtime.hxx
+++ b/basic/source/inc/runtime.hxx
@@ -288,6 +288,7 @@ class SbiRuntime
 
     // #56204 swap out DIM-functionality into help method (step0.cxx)
     void DimImpl(const SbxVariableRef& refVar);
+    bool EvaluateTopOfStackAsBool();
 
     static bool implIsClass( SbxObject const * pObj, const OUString& aClass );
 
diff --git a/basic/source/runtime/runtime.cxx b/basic/source/runtime/runtime.cxx
index 9de5da64d5f2..d1dcd3d74502 100644
--- a/basic/source/runtime/runtime.cxx
+++ b/basic/source/runtime/runtime.cxx
@@ -2975,24 +2975,46 @@ void SbiRuntime::StepJUMP( sal_uInt32 nOp1 )
     pCode = pImg->GetCode() + nOp1;
 }
 
+bool SbiRuntime::EvaluateTopOfStackAsBool()
+{
+    SbxVariableRef tos = PopVar();
+    // In a test e.g. If Null then
+        // will evaluate Null will act as if False
+    if ( bVBAEnabled && tos->IsNull() )
+    {
+        return false;
+    }
+    if ( tos->IsObject() )
+    {
+        //GetBool applied to an Object attempts to dereference and evaluate
+            //the underlying value as Bool. Here, we're checking rather that
+            //it is not null
+        return tos->GetObject();
+    }
+    else
+    {
+        return tos->GetBool();
+    }
+}
+
 // evaluate TOS, conditional jump (+target)
 
 void SbiRuntime::StepJUMPT( sal_uInt32 nOp1 )
 {
-    SbxVariableRef p = PopVar();
-    if( p->GetBool() )
+    if ( EvaluateTopOfStackAsBool() )
+    {
         StepJUMP( nOp1 );
+    }
 }
 
 // evaluate TOS, conditional jump (+target)
 
 void SbiRuntime::StepJUMPF( sal_uInt32 nOp1 )
 {
-    SbxVariableRef p = PopVar();
-    // In a test e.g. If Null then
-        // will evaluate Null will act as if False
-    if( ( bVBAEnabled && p->IsNull() ) || !p->GetBool() )
+    if ( !EvaluateTopOfStackAsBool() )
+    {
         StepJUMP( nOp1 );
+    }
 }
 
 // evaluate TOS, jump into JUMP-table (+MaxVal)