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</o:shapelayout></xml><![endif]--></head><body lang=HU link="#0563C1" vlink="#954F72" style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal><span lang=EN-US>Hi,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Let’s examine this code snippet:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US> void simply_deref_null() {<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> int *p = 0;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> *p ; // no warning?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> *p = 42; // warns!<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> }<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Turns out the NullDereference checker treats the two pointer derefs differently.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>For simply reading through a null pointer is allowed but storing a value is prohibited.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Why don't we prohibit reading through null pointers?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>----<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>By returning a null pointer from a function it suddenly we no longer report an error:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US> int *get() { return 0; }<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> void foo() {<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> int *p = get();<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> *p = 42; // no warning?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US> }<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>According to my investigation the bug actually found and a sink node will be generated in the Exploded graph, but the bug report will be marked as invalid by the ReturnVisitor.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>This behavior could be altered to prevent such suppression from happening by setting the `suppress-null-return-paths` analyzer option to `true`.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Am I right that this is the intentional behavior and if we want to catch bugs like this, then we should enable the aforementioned option?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>/CC NoQ<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>Regards,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Balazs<o:p></o:p></span></p></div></body></html>