fdo#41712: sw: fix crash in layout frame linked lists:

The pPrecede member is not maintained properly when setting the
corresponding pFollow member.
The change in SwTxtFrm::JoinFrm() fixes the crash, the other changes
are perhaps fixes for other crashes...
(regression from cc3d0d182cafef9649e45f4657233ac2221fdd0a)

4 files changed, 24 insertions, 2 deletions

diff --git a/sw/source/core/inc/flowfrm.hxx b/sw/source/core/inc/flowfrm.hxx
index 25a7502ea7a3..32542e8b7ce9 100644
--- a/sw/source/core/inc/flowfrm.hxx
+++ b/sw/source/core/inc/flowfrm.hxx
@@ -145,6 +145,7 @@ protected:
 
 public:
     SwFlowFrm( SwFrm &rFrm );
+    virtual ~SwFlowFrm();
 
     const SwFrm *GetFrm() const            { return &rThis; }
           SwFrm *GetFrm()                  { return &rThis; }
diff --git a/sw/source/core/layout/flowfrm.cxx b/sw/source/core/layout/flowfrm.cxx
index 24f1b518e912..15c678e4fe5a 100644
--- a/sw/source/core/layout/flowfrm.cxx
+++ b/sw/source/core/layout/flowfrm.cxx
@@ -87,12 +87,33 @@ SwFlowFrm::SwFlowFrm( SwFrm &rFrm ) :
     bFlyLock( false )
 {}
 
+SwFlowFrm::~SwFlowFrm()
+{
+    if (m_pFollow)
+    {
+        m_pFollow->m_pPrecede = 0;
+    }
+    if (m_pPrecede)
+    {
+        m_pPrecede->m_pFollow = 0;
+    }
+}
 
 void SwFlowFrm::SetFollow(SwFlowFrm *const pFollow)
 {
+    if (m_pFollow)
+    {
+        assert(this == m_pFollow->m_pPrecede);
+        m_pFollow->m_pPrecede = 0;
+    }
     m_pFollow = pFollow;
     if (m_pFollow != NULL)
     {
+        if (m_pFollow->m_pPrecede) // re-chaining pFollow?
+        {
+            assert(m_pFollow == m_pFollow->m_pPrecede->m_pFollow);
+            m_pFollow->m_pPrecede->m_pFollow = 0;
+        }
         m_pFollow->m_pPrecede = this;
     }
 }
diff --git a/sw/source/core/layout/sectfrm.cxx b/sw/source/core/layout/sectfrm.cxx
index 581c1239732f..4ff80e14fc93 100644
--- a/sw/source/core/layout/sectfrm.cxx
+++ b/sw/source/core/layout/sectfrm.cxx
@@ -222,7 +222,7 @@ void SwSectionFrm::DelEmpty( sal_Bool bRemove )
     }
     else if( HasFollow() )
         GetFollow()->bIsFollow = sal_False;
-    m_pFollow = NULL;
+    SetFollow(0);
     if( pUp )
     {
         Frm().Height( 0 );
diff --git a/sw/source/core/text/frmform.cxx b/sw/source/core/text/frmform.cxx
index 1b3418725d37..0731b1021abf 100644
--- a/sw/source/core/text/frmform.cxx
+++ b/sw/source/core/text/frmform.cxx
@@ -680,8 +680,8 @@ SwCntntFrm *SwTxtFrm::JoinFrm()
         }
     }
     pFoll->Cut();
+    SetFollow(pNxt);
     delete pFoll;
-    m_pFollow = pNxt;
     return pNxt;
 }