<div dir="ltr"><div>RecursiveASTVisitor has an overridable which enables post-order visitation instead of pre-order. Another approach you could take is to match the functions directly, and in the callback fire another matcher - you could manually call clang::ast_matchers::match(MATCHER, Node); (several other overloads exist) which is essentially "fetch me the matched nodes and give me back a data structure on the subtree started by 'Node'." Creating custom matchers local to your code, you can use the "static const auto M = declarative(matcher(syntax()))", or the AST_MATCHER macro, in case your matching requires manually investigating the node via directly calling C++ functions on the node, or calculating some result.</div><div><br></div><div>I don't know how much of this could reasonably be channeled from the checker's code to Clang-Tidy and the execution, or more importantly, how much it could mess up potential other checkers running on the same invocation...</div><div><br></div><div>Another option you could go for is using your check() only as a "data collection" callback and build some (reasonably small!) data structure, and using "void onEndOfTranslationUnit()" at the end to read your data structure, calculate some reasonable result from it, and emit your diagnostics.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Billy O'Mahony via cfe-dev <<a href="mailto:cfe-dev@lists.llvm.org">cfe-dev@lists.llvm.org</a>> ezt írta (időpont: 2019. nov. 25., H, 11:48):<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>Hi,</div><div><br></div><div>I've been writing a project specific clang-tidy check (thanks to Artem and Steve for their help). I've matchers written and working but was seeing some strange things about the order in which my matcher callbacks were being called.<br></div><div><br></div><div>I noticed that in the documentation for MatchFinder it says "
The order of matches is guaranteed to be equivalent to doing a pre-order
traversal on the AST, and applying the matchers in the order in which
they were added to the <a href="https://clang.llvm.org/doxygen/classclang_1_1ast__matchers_1_1MatchFinder.html" title="A class to allow finding matches over the Clang AST." target="_blank">MatchFinder</a>."</div><div><br></div><div>As my checker is checking that certain functions follow certain steps in order (check the "device" arg ptr for NULL, lock the device, do NOT return while the device is locked, unlock the device) I was expecting (depending on) in AST-order of the match callbacks. Not all the device-ptr-check matches first, then all the return matches, then all the etc etc.matches.</div><div><br></div><div><br></div><div>So two questions:<br></div><div>* Can this call-back order be changed somehow? - worth a shot ;)</div><div><br></div><div>* Failing this I can maintain information about the function and line number of all the steps in all the functions and figure out the AST-order from that. But I notice that using srcLocation often returns the same value for several statements (this is because in the code the Lock is actually done in a macro which locks the device but also returns if the lock fails - so I end up with a lock and a return both reporting the same srcLocation - is there a way to determine which comes before which. (I think I came across a way of matching on macros too but I had already written working AST matchers at that point).<br></div><div><br></div><div>Thanks for reading,</div><div><br></div><div>Billy.<br></div><div><br></div><div><br></div><div>--------------</div><div><br></div><div><br></div><div>
<div>Here's an example of one of the type of function I want to check with some examples of errors in the code order:</div><div><br></div><div>int api_foo(device_t *<span>dev</span>) {</div><div> int ret_val = 0;<br></div><div><br></div><div> bar();
// fn calls & decls before api_enter is ok- just don't access <span>dev</span>.</div><div> <span>dev</span>->bla = 1; // NO! device access before api_enter() called</div><div> api_enter(<span>dev</span>); // error if this call is not present exactly once</div><div><br></div><div> if (<span>dev</span>->bla)</div><div> return; // NO! didn't call api_exit before rtn. Also two return points</div><div><br></div><div> if (<span>dev</span>->ma) {</div><div> ret_val = 1;<br></div><div> goto cleanup;</div><div> }</div><div> tweak(<span>dev</span>);<br></div><div><br></div><div>cleanup:</div><div> api_exit(<span>dev</span>); // error if this is not present exactly once<br></div><div> <span>dev</span>->bla = 1; //NO! device access after api_exit()<br></div><div> return ret_val;<br></div><div>}</div>
</div></div>
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