Created attachment 15191 [details]
Testcase

Stripped down version of the manpage on which I first experienced the bug.

SVN commit 526984 by dhaumann:

fix crash
CCBUG:123887


 M  +7 -2      katedialogs.cpp  


--- branches/KDE/3.4/kdelibs/kate/part/katedialogs.cpp #526983:526984
@@ -1604,7 +1604,7 @@
 
   uint lastln =  m_doc->numLines();
   for ( uint l = 0; l <  lastln; l++ )
-    p->writeStdin(  m_doc->textLine( l ), l < lastln );
+    p->writeStdin(  m_doc->textLine( l ) );
 
   p->closeWhenDone();
 }
@@ -1616,10 +1616,15 @@
     m_tmpfile = new KTempFile();
   // put all the data we have in it
   QString stmp;
+  bool readData = false;
   while ( p->readln( stmp, false ) > -1 )
+  {
     *m_tmpfile->textStream() << stmp << endl;
+    readData = true;
+  }
 
-  p->ackRead();
+  if( readData )
+    p->ackRead();
 }
 
 void KateModOnHdPrompt::slotPDone( KProcess *p )

SVN commit 526985 by dhaumann:

fix crash in View Difference
CCBUG: 123887


 M  +20 -3     katedialogs.cpp  


--- branches/KDE/3.5/kdelibs/kate/part/katedialogs.cpp #526984:526985
@@ -1634,7 +1634,7 @@
   // Start a KProcess that creates a diff
   KProcIO *p = new KProcIO();
   p->setComm( KProcess::All );
-  *p << "diff" << "-ub" << "-" <<  m_doc->url().path();
+  *p << "diff" << "-u" << "-" <<  m_doc->url().path();
   connect( p, SIGNAL(processExited(KProcess*)), this, SLOT(slotPDone(KProcess*)) );
   connect( p, SIGNAL(readReady(KProcIO*)), this, SLOT(slotPRead(KProcIO*)) );
 
@@ -1644,7 +1644,7 @@
 
   uint lastln =  m_doc->numLines();
   for ( uint l = 0; l <  lastln; l++ )
-    p->writeStdin(  m_doc->textLine( l ), l < lastln );
+    p->writeStdin( m_doc->textLine( l ) );
 
   p->closeWhenDone();
 }
@@ -1656,15 +1656,32 @@
     m_tmpfile = new KTempFile();
   // put all the data we have in it
   QString stmp;
+  bool dataRead = false;
   while ( p->readln( stmp, false ) > -1 )
+  {
     *m_tmpfile->textStream() << stmp << endl;
+    dataRead = true;
+  }
 
-  p->ackRead();
+  // dominik: only ackRead(), when we *really* read data, otherwise, this slot
+  // is called initity times, which leads to a crash
+  if( dataRead )
+    p->ackRead();
 }
 
 void KateModOnHdPrompt::slotPDone( KProcess *p )
 {
   setCursor( ArrowCursor );
+  if( ! m_tmpfile )
+  {
+    // dominik: there were only whitespace changes, so that the diff returned by
+    // diff(1) has 0 bytes. So slotPRead() is never called, as there is
+    // no data, so that m_tmpfile was never created and thus is NULL.
+    // NOTE: would be nice, if we could produce a fake-diff, so that kompare
+    //       tells us "The files are identical". Right now, we get an ugly
+    //       "Could not parse diff output".
+    m_tmpfile = new KTempFile();
+  }
   m_tmpfile->close();
 
   if ( ! p->normalExit() /*|| p->exitStatus()*/ )

SVN commit 526988 by dhaumann:

fix crash: only call KProcIO::readAck(), when we really read data.
BUG:123887


 M  +21 -3     katedialogs.cpp  


--- trunk/KDE/kdelibs/kate/part/katedialogs.cpp #526987:526988
@@ -1716,7 +1716,7 @@
 
   int lastln =  m_doc->lines();
   for ( int l = 0; l <  lastln; ++l )
-    p->writeStdin(  m_doc->line( l ), l < lastln );
+    p->writeStdin(  m_doc->line( l ) );
 
   p->closeWhenDone();
 }
@@ -1728,16 +1728,26 @@
     m_tmpfile = new KTempFile();
   // put all the data we have in it
   QString stmp;
+  bool readData = false;
   while ( p->readln( stmp, false ) > -1 )
+  {
     *m_tmpfile->textStream() << stmp << endl;
+    readData = true;
+  }
 
-  p->ackRead();
+  // dominik: only ackRead(), when we *really* read data, otherwise, this slot
+  // is called initity times, which leads to a crash
+  if( readData )
+    p->ackRead();
 }
 
 void KateModOnHdPrompt::slotPDone( KProcess *p )
 {
   setCursor( Qt::ArrowCursor );
-  m_tmpfile->close();
+  // dominik: whitespace changes lead to diff with 0 bytes, so that slotPRead is
+  // never called. Thus, m_tmpfile can be NULL
+  if( m_tmpfile )
+    m_tmpfile->close();
 
   if ( ! p->normalExit() /*|| p->exitStatus()*/ )
   {
@@ -1748,6 +1758,14 @@
     return;
   }
 
+  if ( ! m_tmpfile )
+  {
+    KMessageBox::information( this,
+                              i18n("Besides white space changes the files are identical."),
+                              i18n("Diff Output") );
+    return;
+  }
+
   KRun::runURL( m_tmpfile->name(), "text/x-diff", true );
   delete m_tmpfile;
   m_tmpfile = 0;

SVN commit 581699 by dhaumann:

Fix crashes in 'View Difference'
I wasn't aware that we duplicated the code from kate part to kate app and
thus had the same bug in the app, too.
CCBUG: 123887


 M  +16 -2     katemwmodonhddialog.cpp  


--- branches/KDE/3.5/kdebase/kate/app/katemwmodonhddialog.cpp #581698:581699
@@ -237,15 +237,29 @@
     m_tmpfile = new KTempFile();
   // put all the data we have in it
   QString stmp;
-  while ( p->readln( stmp, false ) > -1 )
+  bool dataRead = false;
+  while ( p->readln( stmp, false ) > -1 ) {
     *m_tmpfile->textStream() << stmp << endl;
+    dataRead = true;
+  }
 
-  p->ackRead();
+  if (dataRead)
+    p->ackRead();
 }
 
 void KateMwModOnHdDialog::slotPDone( KProcess *p )
 {
   setCursor( ArrowCursor );
+  if( ! m_tmpfile )
+  {
+    // dominik: there were only whitespace changes, so that the diff returned by
+    // diff(1) has 0 bytes. So slotPRead() is never called, as there is
+    // no data, so that m_tmpfile was never created and thus is NULL.
+    // NOTE: would be nice, if we could produce a fake-diff, so that kompare
+    //       tells us "The files are identical". Right now, we get an ugly
+    //       "Could not parse diff output".
+    m_tmpfile = new KTempFile();
+  }
   m_tmpfile->close();
 
   if ( ! p->normalExit() /*|| p->exitStatus()*/ )