Merge pull request #1959 from jbj/const-pmf

C++: Classify more expressions as constant

cpp/ql/src/semmle/code/cpp/exprs/Expr.qll

@@ -131,6 +131,8 @@ class Expr extends StmtParent, @expr {
     valuebind(_, underlyingElement(this))
     or
     addressConstantExpression(this)
+    or
+    constantTemplateLiteral(this)
   }
 
   /**
@@ -1119,3 +1121,17 @@ private predicate isStandardPlacementNewAllocator(Function operatorNew) {
 
 // Pulled out for performance. See QL-796.
 private predicate hasNoConversions(Expr e) { not e.hasConversion() }
+
+/**
+ * Holds if `e` is a literal of unknown value in a template, or a cast thereof.
+ * We assume that such literals are constant.
+ */
+private predicate constantTemplateLiteral(Expr e) {
+  // Unknown literals in uninstantiated templates could be enum constant
+  // accesses or pointer-to-member literals.
+  e instanceof Literal and
+  e.isFromUninstantiatedTemplate(_) and
+  not exists(e.getValue())
+  or
+  constantTemplateLiteral(e.(Cast).getExpr())
+}

cpp/ql/src/semmle/code/cpp/internal/AddressConstantExpression.qll

@@ -32,6 +32,11 @@ private predicate constantAddressLValue(Expr lvalue) {
   // tells us how it's going to be used.
   lvalue.(FunctionAccess).getType() instanceof RoutineType
   or
+  // Pointer-to-member literals in uninstantiated templates
+  lvalue instanceof Literal and
+  not exists(lvalue.getValue()) and
+  lvalue.isFromUninstantiatedTemplate(_)
+  or
   // String literals have array types and undergo array-to-pointer conversion.
   lvalue instanceof StringLiteral
   or
@@ -61,6 +66,10 @@ private predicate constantAddressPointer(Expr pointer) {
   // tells us how it's going to be used.
   pointer.(FunctionAccess).getType() instanceof FunctionPointerType
   or
+  // Pointer to member function. These accesses are always pointers even though
+  // their type is `RoutineType`.
+  pointer.(FunctionAccess).getTarget() instanceof MemberFunction
+  or
   addressConstantVariable(pointer.(VariableAccess).getTarget()) and
   pointer.getType().getUnderlyingType() instanceof PointerType
   or

cpp/ql/test/library-tests/syntax-zoo/aliased_ssa_sanity.expected

@@ -20,7 +20,7 @@ instructionWithoutSuccessor
 | ms_try_mix.cpp:11:12:11:15 | Chi: call to C |
 | ms_try_mix.cpp:28:12:28:15 | Chi: call to C |
 | ms_try_mix.cpp:48:10:48:13 | Chi: call to C |
-| pointer_to_member.cpp:35:11:35:21 | FieldAddress: {...} |
+| pointer_to_member.cpp:36:11:36:30 | FieldAddress: {...} |
 | stmt_expr.cpp:27:5:27:15 | Store: ... = ... |
 | vla.c:5:9:5:14 | Uninitialized: definition of matrix |
 | vla.c:11:6:11:16 | UnmodeledDefinition: vla_typedef |

cpp/ql/test/library-tests/syntax-zoo/pointer_to_member.cpp

@@ -32,5 +32,16 @@ int usePM(int PM::* pm) {
 void pmIsConst() {
   static const struct {
     int PM::* pm1;
-  } pms = { &PM::x1 };
+    void (PM::* pm2)();
+  } pms = { &PM::x1, &PM::f1 };
 }
+
+template<typename T>
+void pmIsConstT() {
+  static const struct {
+    int T::* pm1;
+    void (T::* pm2)();
+  } pms = { &T::x1, &T::f1 };
+}
+
+template void pmIsConstT<PM>();

cpp/ql/test/library-tests/syntax-zoo/raw_sanity.expected

@@ -7,7 +7,7 @@ missingOperand
 | misc.c:220:3:223:3 | Store: ... = ... | Instruction 'Store' is missing an expected operand with tag 'StoreValue' in function '$@'. | misc.c:219:5:219:26 | IR: assign_designated_init | int assign_designated_init(someStruct*) |
 | misc.c:220:9:223:3 | FieldAddress: {...} | Instruction 'FieldAddress' is missing an expected operand with tag 'Unary' in function '$@'. | misc.c:219:5:219:26 | IR: assign_designated_init | int assign_designated_init(someStruct*) |
 | misc.c:220:9:223:3 | FieldAddress: {...} | Instruction 'FieldAddress' is missing an expected operand with tag 'Unary' in function '$@'. | misc.c:219:5:219:26 | IR: assign_designated_init | int assign_designated_init(someStruct*) |
-| pointer_to_member.cpp:35:13:35:19 | FieldAddress: x1 | Instruction 'FieldAddress' is missing an expected operand with tag 'Unary' in function '$@'. | pointer_to_member.cpp:32:6:32:14 | IR: pmIsConst | void pmIsConst() |
+| pointer_to_member.cpp:36:13:36:19 | FieldAddress: x1 | Instruction 'FieldAddress' is missing an expected operand with tag 'Unary' in function '$@'. | pointer_to_member.cpp:32:6:32:14 | IR: pmIsConst | void pmIsConst() |
 | range_analysis.c:368:10:368:21 | Store: ... ? ... : ... | Instruction 'Store' is missing an expected operand with tag 'StoreValue' in function '$@'. | range_analysis.c:355:14:355:27 | IR: test_ternary01 | unsigned int test_ternary01(unsigned int) |
 | range_analysis.c:369:10:369:36 | Store: ... ? ... : ... | Instruction 'Store' is missing an expected operand with tag 'StoreValue' in function '$@'. | range_analysis.c:355:14:355:27 | IR: test_ternary01 | unsigned int test_ternary01(unsigned int) |
 | range_analysis.c:370:10:370:38 | Store: ... ? ... : ... | Instruction 'Store' is missing an expected operand with tag 'StoreValue' in function '$@'. | range_analysis.c:355:14:355:27 | IR: test_ternary01 | unsigned int test_ternary01(unsigned int) |
@@ -66,7 +66,7 @@ instructionWithoutSuccessor
 | ms_try_mix.cpp:48:10:48:13 | CallSideEffect: call to C |
 | ms_try_mix.cpp:51:5:51:11 | ThrowValue: throw ... |
 | ms_try_mix.cpp:53:13:54:3 | NoOp: { ... } |
-| pointer_to_member.cpp:35:11:35:21 | FieldAddress: {...} |
+| pointer_to_member.cpp:36:11:36:30 | FieldAddress: {...} |
 | static_init_templates.cpp:80:27:80:36 | Convert: (void *)... |
 | static_init_templates.cpp:80:27:80:36 | Convert: (void *)... |
 | static_init_templates.cpp:89:27:89:36 | Convert: (void *)... |
@@ -673,7 +673,8 @@ useNotDominatedByDefinition
 | ms_try_mix.cpp:38:16:38:19 | Operand | Operand 'Operand' is not dominated by its definition in function '$@'. | ms_try_mix.cpp:27:6:27:19 | IR: ms_finally_mix | void ms_finally_mix(int) |
 | ms_try_mix.cpp:41:12:41:15 | Operand | Operand 'Operand' is not dominated by its definition in function '$@'. | ms_try_mix.cpp:27:6:27:19 | IR: ms_finally_mix | void ms_finally_mix(int) |
 | ms_try_mix.cpp:51:5:51:11 | Load | Operand 'Load' is not dominated by its definition in function '$@'. | ms_try_mix.cpp:47:6:47:28 | IR: ms_empty_finally_at_end | void ms_empty_finally_at_end() |
-| pointer_to_member.cpp:35:13:35:19 | Address | Operand 'Address' is not dominated by its definition in function '$@'. | pointer_to_member.cpp:32:6:32:14 | IR: pmIsConst | void pmIsConst() |
+| pointer_to_member.cpp:36:11:36:30 | Unary | Operand 'Unary' is not dominated by its definition in function '$@'. | pointer_to_member.cpp:32:6:32:14 | IR: pmIsConst | void pmIsConst() |
+| pointer_to_member.cpp:36:13:36:19 | Address | Operand 'Address' is not dominated by its definition in function '$@'. | pointer_to_member.cpp:32:6:32:14 | IR: pmIsConst | void pmIsConst() |
 | stmt_expr.cpp:30:20:30:21 | Operand | Operand 'Operand' is not dominated by its definition in function '$@'. | stmt_expr.cpp:21:6:21:6 | IR: g | void stmtexpr::g(int) |
 | stmt_expr.cpp:31:16:31:18 | Load | Operand 'Load' is not dominated by its definition in function '$@'. | stmt_expr.cpp:21:6:21:6 | IR: g | void stmtexpr::g(int) |
 | try_catch.cpp:21:13:21:24 | Address | Operand 'Address' is not dominated by its definition in function '$@'. | try_catch.cpp:19:6:19:23 | IR: throw_from_nonstmt | void throw_from_nonstmt(int) |

cpp/ql/test/library-tests/syntax-zoo/staticlocals.cpp

@@ -29,4 +29,16 @@ void f2() {
     static C c{};
 }
 
+template<typename T>
+struct Sizeof {
+  enum sizeof_enum { value = sizeof(T) };
+};
+
+template<typename T>
+void f3() {
+  static int i = Sizeof<T>::value;
+}
+
+template void f3<int>();
+
 }

cpp/ql/test/library-tests/syntax-zoo/tellDifferent.expected

@@ -1,3 +1,3 @@
-| staticlocals__staticlocals_f2 | file://:0:0:0:0 | call to C | staticlocals.cpp:30:1:30:1 | return ... | Standard edge, only from QL |
-| staticlocals__staticlocals_f2 | file://:0:0:0:0 | initializer for c | file://:0:0:0:0 | call to C | Standard edge, only from QL |
-| staticlocals__staticlocals_f2 | staticlocals.cpp:29:5:29:17 | declaration | file://:0:0:0:0 | initializer for c | Standard edge, only from QL |
+| staticlocals__staticlocals_f2 | file://:0:0:0:0 | call to C | staticlocals.cpp:30:1:30:1 | return ... | Standard edge, only from QL |  |
+| staticlocals__staticlocals_f2 | file://:0:0:0:0 | initializer for c | file://:0:0:0:0 | call to C | Standard edge, only from QL |  |
+| staticlocals__staticlocals_f2 | staticlocals.cpp:29:5:29:17 | declaration | file://:0:0:0:0 | initializer for c | Standard edge, only from QL |  |

cpp/ql/test/library-tests/syntax-zoo/tellDifferent.ql

@@ -1,5 +1,13 @@
 import Compare
 
+string describeTemplate(ControlFlowNode node) {
+  node.isFromTemplateInstantiation(_) and
+  result = "instantiation"
+  or
+  node.isFromUninstantiatedTemplate(_) and
+  result = "uninstantiated"
+}
+
 from ControlFlowNode n1, ControlFlowNode n2, string msg
 where differentEdge(n1, n2, msg)
-select getScopeName(n1), n1, n2, msg
+select getScopeName(n1), n1, n2, msg, concat(describeTemplate(n1), ", ")

cpp/ql/test/library-tests/syntax-zoo/unaliased_ssa_sanity.expected

@@ -29,7 +29,7 @@ instructionWithoutSuccessor
 | ms_try_mix.cpp:11:12:11:15 | CallSideEffect: call to C |
 | ms_try_mix.cpp:28:12:28:15 | CallSideEffect: call to C |
 | ms_try_mix.cpp:48:10:48:13 | CallSideEffect: call to C |
-| pointer_to_member.cpp:35:11:35:21 | FieldAddress: {...} |
+| pointer_to_member.cpp:36:11:36:30 | FieldAddress: {...} |
 | stmt_expr.cpp:27:5:27:15 | Store: ... = ... |
 | vla.c:5:9:5:14 | Uninitialized: definition of matrix |
 | vla.c:11:6:11:16 | UnmodeledDefinition: vla_typedef |