Fix #11289 FP wrongPrintfScanfArgNum - snprintf with parameter pack (#4644)

Author: chrchr-github

lib/checkio.cpp

@@ -1306,6 +1306,8 @@ void CheckIO::checkFormatString(const Token * const tok,
     // Count printf/scanf parameters..
     int numFunction = 0;
     while (argListTok2) {
+        if (Token::Match(argListTok2, "%name% ...")) // bailout for parameter pack
+            return;
         numFunction++;
         argListTok2 = argListTok2->nextArgument(); // Find next argument
     }

test/testio.cpp

@@ -80,6 +80,7 @@ class TestIO : public TestFixture {
         TEST_CASE(testPrintfAuto); // #8992
         TEST_CASE(testPrintfParenthesis); // #8489
         TEST_CASE(testStdDistance); // #10304
+        TEST_CASE(testParameterPack); // #11289
     }
 
 #define check(...) check_(__FILE__, __LINE__, __VA_ARGS__)
@@ -4868,6 +4869,16 @@ class TestIO : public TestFixture {
               "}", /*inconclusive*/ false, /*portability*/ true);
         ASSERT_EQUALS("", errout.str());
     }
+
+    void testParameterPack() { // #11289
+        check("template <typename... Args> auto f(const char* format, const Args&... args) {\n"
+              "    return snprintf(nullptr, 0, format, args...);\n"
+              "}\n"
+              "void g() {\n"
+              "    f(\"%d%d\", 1, 2);\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+    }
 };
 
 REGISTER_TEST(TestIO)