[clang-tidy] Fix a crash on invalid code for memset-usage check.

clang-tools-extra/clang-tidy/bugprone/SuspiciousMemsetUsageCheck.cpp

auto MemsetDecl =
                    parameterCountIs(3),
                    hasParameter(0, hasType(pointerType(pointee(voidType())))),
                    hasParameter(1, hasType(isInteger())),
                    hasParameter(2, hasType(isInteger())));
 
   // Look for memset(x, '0', z). Probably memset(x, 0, z) was intended.
   Finder->addMatcher(
       callExpr(
-          callee(MemsetDecl),
+          callee(MemsetDecl), argumentCountIs(3),
           hasArgument(1, characterLiteral(equals(static_cast<unsigned>('0')))
                              .bind("char-zero-fill")),
           unless(hasArgument(
               0, anyOf(hasType(pointsTo(isAnyCharacter())),
                        hasType(arrayType(hasElementType(isAnyCharacter()))))))),
       this);
 
   // Look for memset with an integer literal in its fill_char argument.
   // Will check if it gets truncated.
   Finder->addMatcher(
-      callExpr(callee(MemsetDecl),
+      callExpr(callee(MemsetDecl), argumentCountIs(3),
                hasArgument(1, integerLiteral().bind("num-fill"))),
       this);
 
   // Look for memset(x, y, 0) as that is most likely an argument swap.
   Finder->addMatcher(
-      callExpr(callee(MemsetDecl),
+      callExpr(callee(MemsetDecl), argumentCountIs(3),
                unless(hasArgument(1, anyOf(characterLiteral(equals(
                                                static_cast<unsigned>('0'))),
                                            integerLiteral()))))
           .bind("call"),
       this);
 }
 
 void SuspiciousMemsetUsageCheck::check(const MatchFinder::MatchResult &Result) {

clang-tools-extra/test/clang-tidy/checkers/bugprone-suspicious-memset-usage.c

+// RUN: %check_clang_tidy  -expect-clang-tidy-error  %s bugprone-suspicious-memset-usage %t
+
+void *memset(void *, int, __SIZE_TYPE__);
+void *memset(void *);
+// CHECK-MESSAGES: :[[@LINE-1]]:7: error: conflicting types for 'memset'
+
+void test() {
+  // no crash
+  memset(undefine);
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: error: use of undeclared identifier
+}