[PATCH] D87449: [clang-tidy] Add new check for SEI CERT rule SIG30-C

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang-tools-extra/clang-tidy/cert/SignalHandlerCheck.cpp:117-118
+    FunctionCallCollector Collector{[&CalledFunctions](const CallExpr *CE) {
+      if (isa<FunctionDecl>(CE->getCalleeDecl()))
+        CalledFunctions.push_back(CE);
+    }};
----------------
balazske wrote:
> aaron.ballman wrote:
> > balazske wrote:
> > > aaron.ballman wrote:
> > > > aaron.ballman wrote:
> > > > > balazske wrote:
> > > > > > aaron.ballman wrote:
> > > > > > > For correctness, I think you need to handle more than just calls to function declarations -- for instance, this should be just as problematic:
> > > > > > > ```
> > > > > > > void some_signal_handler(int sig) {
> > > > > > >   []{ puts("this should not be an escape hatch for the check); }();
> > > > > > > }
> > > > > > > ```
> > > > > > > even though the call expression in the signal handler doesn't resolve back to a function declaration. (Similar for blocks instead of lambdas.) WDYT?
> > > > > > I do not know how many other cases could be there. Probably this can be left for future  improvement, the checker is mainly usable for C code then. There is a `clang::CallGraph` functionality that could be used instead of `FunctionCallCollector` but the `CallExpr` for the calls is not provided by it so it does not work for this case. Maybe there is other similar functionality that is usable?
> > > > > Given that we want it in the CERT module, we should try to ensure it follows the rule as closely as we can. I went and checked what the C++ rules say about this and... it was interesting to notice that SIG30-C is not one of the C rules included by reference in C++ (https://wiki.sei.cmu.edu/confluence/pages/viewpage.action?pageId=88046336).
> > > > > 
> > > > > It's not clear to me that this rule was accidentally tagged as `not-for-cpp` or not, so I'd say it's fine to ignore lambdas for the moment but we may have some follow-up work if CERT changes the rule to be included in C++. My recommendation is: make the check a C-only check for now, document it as such, and I'll ping the folks at CERT to see if this rule was mistagged or not. WDYT?
> > > > Ah, this rule really is a C-only rule, because https://wiki.sei.cmu.edu/confluence/display/cplusplus/MSC54-CPP.+A+signal+handler+must+be+a+plain+old+function is the C++ rule. So I think the SIG30-C checker should be run in C-only mode and we can ignore the C++isms in it.
> > > > 
> > > > FWIW, we have an ongoing discussion about MSC54-CPP in https://reviews.llvm.org/D33825.
> > > Probably this checker can be merged with the other in D33825. According to cppreference (https://en.cppreference.com/w/cpp/utility/program/signal) the check for the called functions should be present for C++ too. And the other checker should do a similar lookup of called functions as this checker, including lambdas and C++ specific things.
> > While you would think that, it's a bit more complicated unfortunately. The C++ committee has been moving forward with this paper http://wg21.link/p0270 so that C++ is no longer tied to the same constraints as C. That may suggest that separate checks are appropriate, or it may still mean we want to merge the checks into one.
> I think it is more convenient to merge the two checkers. The visitation of called functions goes the same way, the support for C++ constructs should not cause problems if used with C code. The handling of a detected function can be different code for C and C++ mode but if there are similar parts code can be reused.
> Otherwise code of this checker would be a better starting point for "SignalHandlerMustBePlainOldFunctionCheck" because it handles detection of the `signal` function already better specially for C++.
Okay, I could see that. Would you like to collaborate with the author of D33825 to see if you can produce a combined check? Or would you prefer to wait for that review to land for C++ and then modify it for C? (Or some other approach entirely?)


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  https://reviews.llvm.org/D87449/new/

https://reviews.llvm.org/D87449