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<p class="MsoNormal"><span style="color:#1F497D">I generally followed Artem’s suggestions (for my approach) and things worked out okay. Specifically:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">void MyChecker::checkPreCall(const CallEvent &Call, CheckerContext &ChCtx) const {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> const Stmt *Parent = ChCtx.getStackFrame()->getParentMap().getParent(Call.getOriginExpr());<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (!Parent || !isa<CompoundStmt>(Parent))<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> // Proceed with my checks.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Then I generalized this a bit, but still in a syntactic way (not in the path-sensitive way Artem suggested). The idea is to follow the parent chain to get the first non-Expr statement containing the call, and
then check if that statement makes use of the expression value (which is built from the call’s return value).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">bool isReturnValueUsed(const CallEvent &Call, CheckerContext &ChCtx) {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> const ParentMap &PM = ChCtx.getStackFrame()->getParentMap();<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> const Expr *TopLevelExpr = Call.getOriginExpr();<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> const Stmt *Containing Stmt = PM.getParent(TopLevelExpr);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> while (ContainingStmt && isa<Expr>(ContainingStmt)) {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (is<BinaryOperator>(ContainingStmt) && cast<BinaryOperator>(ContainingStmt)->isAssignmentOp())<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return true; // return value is used in an assignment<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> TopLevelExpr = cast<Expr>(ContainingStmt);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> ContainingStmt = PM.getParent(TopLevelExpr);<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> }<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (!ContainingStmt)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return false;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (isa<DeclStmt>(ContainingStmt))<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return true; // return value is used in an initialization<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (isa<IfStmt>(ContainingStmt) && TopLevelExpr == cast<IfStmt>(ContainingStmt)->getCond())<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return true; // return value is used in an if condition<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (isa<SwitchStmt>(ContainingStmt) && TopLevelExpr == cast<SwitchStmt>(ContainingStmt)->getCond())<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return true; // return value is used in a switch condition<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (isa<WhileStmt>(ContainingStmt) && TopLevelExpr == cast<WhileStmt>(ContainingStmt)->getCond())<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return true; // return value is used in a while loop condition<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (isa<DoStmt>(ContainingStmt) && TopLevelExpr == cast<DoStmt>(ContainingStmt)->getCond())<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return true; // return value is used in do loop condition<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (isa<ReturnStmt>(ContainingStmt) && TopLevelExpr == cast<ReturnStmt>(ContainingStmt)->getRetValue())<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return true; // return value is used to construct a higher-level return value<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return false;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">void MyChecker::checkPreCall(const CallEvent &Call, CheckerContext &ChCtx) const {<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> const Stmt *Parent = ChCtx.getStackFrame()->getParentMap().getParent(Call.getOriginExpr());<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> if (!Parent || !isa<CompoundStmt>(Parent))<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> return;<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New""> // Proceed with my checks.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Courier New"">}<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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