[analyzer] StdLibraryFunctionsChecker: Add test for function with default parameter

[Szelethus]

Yay.

clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp

llvm::StringMap<Summaries> TestFunctionSummaryMap = {
                  .ArgConstraint(
                      ArgumentCondition(1U, WithinRange, SingleValue(1)))}},
         {"__arg_constrained_twice",
          Summaries{Summary(ArgTypes{IntTy}, RetType{IntTy}, EvalCallAsPure)
                        .ArgConstraint(
                            ArgumentCondition(0U, OutOfRange, SingleValue(1)))
                        .ArgConstraint(
                            ArgumentCondition(0U, OutOfRange, SingleValue(2)))}},
+        {"__defaultparam", Summaries{Summary(ArgTypes{Irrelevant, IntTy},
+                                             RetType{IntTy}, EvalCallAsPure)
+                                         .ArgConstraint(NotNull(ArgNo(0)))}},
     };
     for (auto &E : TestFunctionSummaryMap) {
       auto InsertRes =
           FunctionSummaryMap.insert({std::string(E.getKey()), E.getValue()});
       assert(InsertRes.second &&
              "Test functions must not clash with modeled functions");
       (void)InsertRes;
     }

clang/test/Analysis/std-c-library-functions-arg-constraints.cpp

+// RUN: %clang_analyze_cc1 %s \
+// RUN:   -analyzer-checker=core \
+// RUN:   -analyzer-checker=apiModeling.StdCLibraryFunctions \
+// RUN:   -analyzer-checker=apiModeling.StdCLibraryFunctionArgs \
+// RUN:   -analyzer-checker=debug.StdCLibraryFunctionsTester \
+// RUN:   -analyzer-checker=debug.ExprInspection \
+// RUN:   -analyzer-config eagerly-assume=false \
+// RUN:   -triple i686-unknown-linux \
+// RUN:   -verify
+
+void clang_analyzer_eval(int);
+
+int __defaultparam(void *, int y = 3);
+
+void test_arg_constraint_on_fun_with_default_param() {
+  __defaultparam(nullptr); // \
+  // expected-warning{{Function argument constraint is not satisfied}}
+}