Merge pull request #830 from ian-semmle/constexpr

nickrolfe · web-flow · commit 53de2d8d3e6f · 2019-02-25T22:11:24.000Z
C++: Add Function.{isDeclaredConstexpr,isConstexpr}() predicates
diff --git a/change-notes/1.20/analysis-cpp.md b/change-notes/1.20/analysis-cpp.md
@@ -36,3 +36,4 @@
 
 * There is a new `Namespace.isInline()` predicate, which holds if the namespace was declared as `inline namespace`.
 * The `Expr.isConstant()` predicate now also holds for _address constant expressions_, which are addresses that will be constant after the program has been linked. These address constants do not have a result for `Expr.getValue()`.
+* There are new `Function.isDeclaredConstexpr()` and `Function.isConstexpr()` predicates. They can be used to tell whether a function was declared as `constexpr`, and whether it actually is `constexpr`.
diff --git a/cpp/ql/src/semmle/code/cpp/Function.qll b/cpp/ql/src/semmle/code/cpp/Function.qll
@@ -103,6 +103,27 @@ class Function extends Declaration, ControlFlowNode, AccessHolder, @function {
     function_defaulted(underlyingElement(this))
   }
 
+  /**
+   * Holds if this function is declared to be `constexpr`.
+   */
+  predicate isDeclaredConstexpr() {
+    this.hasSpecifier("declared_constexpr")
+  }
+
+  /**
+   * Holds if this function is `constexpr`. Normally, this holds if and
+   * only if `isDeclaredConstexpr()` holds, but in some circumstances
+   * they differ. For example, with
+   * ```
+   * int f(int i) { return 6; }
+   * template <typename T> constexpr int g(T x) { return f(x); }
+   * ```
+   * `g<int>` is declared constexpr, but is not constexpr.
+   */
+  predicate isConstexpr() {
+    this.hasSpecifier("is_constexpr")
+  }
+
   /**
    * Holds if this function is declared with `__attribute__((naked))` or
    * `__declspec(naked)`.
diff --git a/cpp/ql/test/library-tests/clang_ms/element.expected b/cpp/ql/test/library-tests/clang_ms/element.expected
@@ -67,6 +67,7 @@
 | file://:0:0:0:0 | const mystruct & |
 | file://:0:0:0:0 | declaration of 1st parameter |
 | file://:0:0:0:0 | declaration of 1st parameter |
+| file://:0:0:0:0 | declared_constexpr |
 | file://:0:0:0:0 | decltype(nullptr) |
 | file://:0:0:0:0 | definition of fp_offset |
 | file://:0:0:0:0 | definition of gp_offset |
@@ -86,6 +87,7 @@
 | file://:0:0:0:0 | implicit_int |
 | file://:0:0:0:0 | inline |
 | file://:0:0:0:0 | int |
+| file://:0:0:0:0 | is_constexpr |
 | file://:0:0:0:0 | long |
 | file://:0:0:0:0 | long double |
 | file://:0:0:0:0 | long long |
diff --git a/cpp/ql/test/library-tests/conditions/elements.expected b/cpp/ql/test/library-tests/conditions/elements.expected
@@ -42,6 +42,7 @@
 | file://:0:0:0:0 | const |
 | file://:0:0:0:0 | const __va_list_tag |
 | file://:0:0:0:0 | const __va_list_tag & |
+| file://:0:0:0:0 | declared_constexpr |
 | file://:0:0:0:0 | decltype(nullptr) |
 | file://:0:0:0:0 | definition of <error> |
 | file://:0:0:0:0 | definition of fp_offset |
@@ -63,6 +64,7 @@
 | file://:0:0:0:0 | initializer for <error> |
 | file://:0:0:0:0 | inline |
 | file://:0:0:0:0 | int |
+| file://:0:0:0:0 | is_constexpr |
 | file://:0:0:0:0 | long |
 | file://:0:0:0:0 | long double |
 | file://:0:0:0:0 | long long |
diff --git a/cpp/ql/test/library-tests/functions/constexpr/constexpr.cpp b/cpp/ql/test/library-tests/functions/constexpr/constexpr.cpp
@@ -0,0 +1,24 @@
+
+constexpr int fun_constexpr();
+int fun_not_constexpr();
+
+constexpr int overloaded_fun(int i) {
+    return 5;
+}
+
+int overloaded_fun(float f) {
+    return 6;
+}
+
+template <typename T>
+constexpr int template_fun(T t) {
+    return overloaded_fun(t);
+}
+
+void caller(void) {
+    int i;
+    float f;
+    template_fun(i);
+    template_fun(f);
+}
+
diff --git a/cpp/ql/test/library-tests/functions/constexpr/constexpr.expected b/cpp/ql/test/library-tests/functions/constexpr/constexpr.expected
@@ -0,0 +1,10 @@
+| constexpr.cpp:2:15:2:27 | fun_constexpr | int fun_constexpr() | true | true |
+| constexpr.cpp:3:5:3:21 | fun_not_constexpr | int fun_not_constexpr() | false | false |
+| constexpr.cpp:5:15:5:28 | overloaded_fun | int overloaded_fun(int) | true | true |
+| constexpr.cpp:9:5:9:18 | overloaded_fun | int overloaded_fun(float) | false | false |
+| constexpr.cpp:14:15:14:15 | template_fun | int template_fun<float>(float) | true | false |
+| constexpr.cpp:14:15:14:15 | template_fun | int template_fun<int>(int) | true | true |
+| constexpr.cpp:14:15:14:26 | template_fun | int template_fun<T>(T) | true | true |
+| constexpr.cpp:18:6:18:11 | caller | void caller() | false | false |
+| file://:0:0:0:0 | operator= | __va_list_tag& __va_list_tag::operator=(__va_list_tag const&) | false | false |
+| file://:0:0:0:0 | operator= | __va_list_tag& __va_list_tag::operator=(__va_list_tag&&) | false | false |
diff --git a/cpp/ql/test/library-tests/functions/constexpr/constexpr.ql b/cpp/ql/test/library-tests/functions/constexpr/constexpr.ql
@@ -0,0 +1,7 @@
+import cpp
+import semmle.code.cpp.Print
+
+from Function f
+select f, getIdentityString(f),
+       any(boolean b | if f.isDeclaredConstexpr() then b = true else b = false),
+       any(boolean b | if f.isConstexpr() then b = true else b = false)
diff --git a/cpp/ql/test/library-tests/specifiers2/specifiers2.expected b/cpp/ql/test/library-tests/specifiers2/specifiers2.expected
@@ -11,6 +11,8 @@
 | Function | specifiers2pp.cpp:8:7:8:7 | MyClass | MyClass | extern |
 | Function | specifiers2pp.cpp:8:7:8:7 | MyClass | MyClass | inline |
 | Function | specifiers2pp.cpp:8:7:8:7 | MyClass | MyClass | inline |
+| Function | specifiers2pp.cpp:8:7:8:7 | MyClass | MyClass | is_constexpr |
+| Function | specifiers2pp.cpp:8:7:8:7 | MyClass | MyClass | is_constexpr |
 | Function | specifiers2pp.cpp:8:7:8:7 | MyClass | MyClass | public |
 | Function | specifiers2pp.cpp:8:7:8:7 | MyClass | MyClass | public |
 | Function | specifiers2pp.cpp:8:7:8:7 | operator= | operator= | extern |
@@ -41,6 +43,8 @@
 | Function | specifiers2pp.cpp:24:7:24:7 | MyClass2 | MyClass2 | inline |
 | Function | specifiers2pp.cpp:24:7:24:7 | MyClass2 | MyClass2 | inline |
 | Function | specifiers2pp.cpp:24:7:24:7 | MyClass2 | MyClass2 | inline |
+| Function | specifiers2pp.cpp:24:7:24:7 | MyClass2 | MyClass2 | is_constexpr |
+| Function | specifiers2pp.cpp:24:7:24:7 | MyClass2 | MyClass2 | is_constexpr |
 | Function | specifiers2pp.cpp:24:7:24:7 | MyClass2 | MyClass2 | public |
 | Function | specifiers2pp.cpp:24:7:24:7 | MyClass2 | MyClass2 | public |
 | Function | specifiers2pp.cpp:24:7:24:7 | MyClass2 | MyClass2 | public |
diff --git a/cpp/ql/test/library-tests/templates/instantiations_functions/elements.expected b/cpp/ql/test/library-tests/templates/instantiations_functions/elements.expected
@@ -88,6 +88,7 @@
 | file://:0:0:0:0 | declaration of 1st parameter |
 | file://:0:0:0:0 | declaration of 1st parameter |
 | file://:0:0:0:0 | declaration of 1st parameter |
+| file://:0:0:0:0 | declared_constexpr |
 | file://:0:0:0:0 | decltype(nullptr) |
 | file://:0:0:0:0 | definition of fp_offset |
 | file://:0:0:0:0 | definition of gp_offset |
@@ -111,6 +112,7 @@
 | file://:0:0:0:0 | int |
 | file://:0:0:0:0 | int & |
 | file://:0:0:0:0 | int * |
+| file://:0:0:0:0 | is_constexpr |
 | file://:0:0:0:0 | long |
 | file://:0:0:0:0 | long double |
 | file://:0:0:0:0 | long long |
diff --git a/cpp/ql/test/library-tests/unnamed/elements.expected b/cpp/ql/test/library-tests/unnamed/elements.expected
@@ -35,6 +35,7 @@
 | file://:0:0:0:0 | char16_t | Other |
 | file://:0:0:0:0 | char32_t | Other |
 | file://:0:0:0:0 | const | Other |
+| file://:0:0:0:0 | declared_constexpr | Other |
 | file://:0:0:0:0 | decltype(nullptr) | Other |
 | file://:0:0:0:0 | definition of fp_offset | Other |
 | file://:0:0:0:0 | definition of gp_offset | Other |
@@ -56,6 +57,7 @@
 | file://:0:0:0:0 | int | Other |
 | file://:0:0:0:0 | int * | Other |
 | file://:0:0:0:0 | int[0] | Other |
+| file://:0:0:0:0 | is_constexpr | Other |
 | file://:0:0:0:0 | long | Other |
 | file://:0:0:0:0 | long double | Other |
 | file://:0:0:0:0 | long long | Other |

Original file line number	Diff line number	Diff line change
`@@ -36,3 +36,4 @@`
`36`	`36`
`37`	`37`	* There is a new `Namespace.isInline()` predicate, which holds if the namespace was declared as `inline namespace`.
`38`	`38`	* The `Expr.isConstant()` predicate now also holds for _address constant expressions_, which are addresses that will be constant after the program has been linked. These address constants do not have a result for `Expr.getValue()`.
	`39`	+* There are new `Function.isDeclaredConstexpr()` and `Function.isConstexpr()` predicates. They can be used to tell whether a function was declared as `constexpr`, and whether it actually is `constexpr`.