created RandomSegmentationFaults tip

Author: stephengaito

docs/TipsAndTricks/RandomSegmentationFaults.md

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+# Solving random segmenation faults...
+
+Ideally the source code *should* be littered with ANSI-C `assert`ions.
+These are indispensable in detecting segmentation faults due to
+dereferencing null pointers. 
+
+Obviously there are not enough... so consider adding more!
+
+One way to track down the source of a random segmentation fault, 
+is to litter the pdf2htmlEX and/or poppler source code with
+printfs... This will allow you to detect the last working code, 
+and this might suggest where to start reading the code in detail.
+
+## Poppler reference counting
+
+Poppler uses object reference counting. Unfortunately the assumption
+about "who" is responsible for incrementing and decrementing these
+refernce counts *does* change between poppler releases. This means
+that between poppler releases the pdf2htmlEX code should include
+new increments or decrements *or* now has too many...
+
+**Solution:** Check all {inc,dec}RefCnt uses...
+from poppler-0.68.0 the USER (i.e. pdf2htmlEX) is supposed to
+incRefCnt as well as decRefCnt.
+