C++: Ensure instantiation. In an upcoming PR it's important to ensure that

templated constructors are instantiated. So this commit ensures that all
the constructors that were not previously instantiated are now instantiated.

Author: MathiasVP

cpp/ql/test/library-tests/dataflow/external-models/azure.cpp

@@ -317,6 +317,7 @@ void test_RawResponse(Azure::Core::Http::RawResponse& resp) {
 }
 
 void test_GetHeader() {
+  std::pair<std::string, std::string>();
   Azure::Core::Http::Request request(Azure::Core::Http::Get, Azure::Core::Url("http://example.com"));
   {
     auto headerValue = request.GetHeader("Content-Type").Value();

cpp/ql/test/library-tests/dataflow/taint-tests/map.cpp

@@ -219,7 +219,7 @@ void test_map()
 	sink(m22); // $ ast,ir
 
 	// erase, clear
-	std::map<const char *, const char *> m23;
+	std::map<const char *, const char *> m23; std::map<const char *, const char *>::value_type(source(), source()); // ensure instantiation
 	m23.insert(std::pair<const char *, const char *>(source(), source()));
 	m23.insert(std::pair<const char *, const char *>(source(), source()));
 	sink(m23); // $ ast,ir=223:49 ast,ir=224:49
@@ -229,7 +229,7 @@ void test_map()
 	sink(m23); // $ SPURIOUS: ast,ir=223:49 ast,ir=224:49
 
 	// emplace, emplace_hint
-	std::map<const char *, const char *> m24, m25;
+	std::map<const char *, const char *> m24, m25; std::map<const char *, const char *>::value_type("abc", source()); // force the template instantiation
 	sink(m24.emplace("abc", "def").first);
 	sink(m24);
 	sink(m24.emplace("abc", source()).first);
@@ -406,7 +406,7 @@ void test_unordered_map()
 	sink(m28); // $ MISSING: ast,ir
 
 	// additional try_emplace test cases
-	std::unordered_map<const char *, std::pair<int, int>> m29, m30, m31, m32;
+	std::unordered_map<const char *, std::pair<int, int>> m29, m30, m31, m32; std::pair<int, int> inst1(0, 0); int x; std::pair<int, int> inst2(x, x);
 	sink(m29.try_emplace("abc", 1, 2));
 	sink(m29);
 	sink(m29["abc"]);