Merge pull request #1012 from ian-semmle/constexpr

C++: Add Variable.isConstexpr()

Author: nickrolfe

change-notes/1.20/analysis-cpp.md

@@ -39,3 +39,4 @@
 * 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`.
+* There is a new `Variable.isConstexpr()` predicate. It can be used to tell whether a variable is `constexpr`.

cpp/ql/src/semmle/code/cpp/Variable.qll

@@ -121,6 +121,13 @@ class Variable extends Declaration, @variable {
     result.getLValue() = this.getAnAccess()
   }
 
+  /**
+   * Holds if this variable is `constexpr`.
+   */
+  predicate isConstexpr() {
+    this.hasSpecifier("is_constexpr")
+  }
+
   /**
    * Holds if this variable is constructed from `v` as a result
    * of template instantiation. If so, it originates either from a template

cpp/ql/test/library-tests/variables/constexpr/constexpr.cpp

@@ -0,0 +1,6 @@
+
+constexpr int var_constexpr = 5;
+int var_not_constexpr_initialised = 6;
+const int var_not_constexpr_const = 7;
+int var_not_constexpr;
+

cpp/ql/test/library-tests/variables/constexpr/constexpr.expected

@@ -0,0 +1,10 @@
+| constexpr.cpp:2:15:2:27 | var_constexpr | true |
+| constexpr.cpp:3:5:3:33 | var_not_constexpr_initialised | false |
+| constexpr.cpp:4:11:4:33 | var_not_constexpr_const | false |
+| constexpr.cpp:5:5:5:21 | var_not_constexpr | false |
+| file://:0:0:0:0 | fp_offset | false |
+| file://:0:0:0:0 | gp_offset | false |
+| file://:0:0:0:0 | overflow_arg_area | false |
+| file://:0:0:0:0 | p#0 | false |
+| file://:0:0:0:0 | p#0 | false |
+| file://:0:0:0:0 | reg_save_area | false |

cpp/ql/test/library-tests/variables/constexpr/constexpr.ql

@@ -0,0 +1,5 @@
+import cpp
+
+from Variable v
+select v,
+       any(boolean b | if v.isConstexpr() then b = true else b = false)