C++: Fix IR edge case where there are no function calls taking an argument

cpp/ql/lib/semmle/code/cpp/ir/internal/IRCppLanguage.qll

@@ -67,8 +67,13 @@ class Class = Cpp::Class; // Used for inheritance conversions
 predicate hasCaseEdge(string minValue, string maxValue) { hasCaseEdge(_, minValue, maxValue) }
 
 predicate hasPositionalArgIndex(int argIndex) {
-  exists(Cpp::FunctionCall call | exists(call.getArgument(argIndex))) or
+  exists(Cpp::FunctionCall call | exists(call.getArgument(argIndex)))
+  or
   exists(Cpp::BuiltInOperation op | exists(op.getChild(argIndex)))
+  or
+  // Ensure we are always able to output the argument of a call to the delete operator.
+  exists(Cpp::DeleteExpr d) and
+  argIndex = 0
 }
 
 predicate hasAsmOperandIndex(int operandIndex) {

cpp/ql/test/library-tests/ir/no-function-calls/PrintAST.expected

@@ -0,0 +1,36 @@
+#-----| [CopyAssignmentOperator] __va_list_tag& __va_list_tag::operator=(__va_list_tag const&)
+#-----|   <params>: 
+#-----|     getParameter(0): [Parameter] (unnamed parameter 0)
+#-----|         Type = [LValueReferenceType] const __va_list_tag &
+#-----| [MoveAssignmentOperator] __va_list_tag& __va_list_tag::operator=(__va_list_tag&&)
+#-----|   <params>: 
+#-----|     getParameter(0): [Parameter] (unnamed parameter 0)
+#-----|         Type = [RValueReferenceType] __va_list_tag &&
+#-----| [Operator,TopLevelFunction] void operator delete(void*)
+#-----|   <params>: 
+#-----|     getParameter(0): [Parameter] (unnamed parameter 0)
+#-----|         Type = [VoidPointerType] void *
+test.cpp:
+#    5| [TopLevelFunction] void foo(int*)
+#    5|   <params>: 
+#    5|     getParameter(0): [Parameter] x
+#    5|         Type = [IntPointerType] int *
+#    5|   getEntryPoint(): [BlockStmt] { ... }
+#    6|     getStmt(0): [ExprStmt] ExprStmt
+#    6|       getExpr(): [DeleteExpr] delete
+#    6|           Type = [VoidType] void
+#    6|           ValueCategory = prvalue
+#    6|         getExprWithReuse(): [VariableAccess] x
+#    6|             Type = [IntPointerType] int *
+#    6|             ValueCategory = prvalue(load)
+#    7|     getStmt(1): [ReturnStmt] return ...
+#    9| [TopLevelFunction] void bar()
+#    9|   <params>: 
+#   11| [TopLevelFunction] void jazz()
+#   11|   <params>: 
+#   11|   getEntryPoint(): [BlockStmt] { ... }
+#   12|     getStmt(0): [ExprStmt] ExprStmt
+#   12|       getExpr(): [FunctionCall] call to bar
+#   12|           Type = [VoidType] void
+#   12|           ValueCategory = prvalue
+#   13|     getStmt(1): [ReturnStmt] return ...

cpp/ql/test/library-tests/ir/no-function-calls/PrintAST.ql

@@ -0,0 +1,11 @@
+/**
+ * @kind graph
+ */
+
+private import cpp
+private import semmle.code.cpp.PrintAST
+private import PrintConfig
+
+private class PrintConfig extends PrintAstConfiguration {
+  override predicate shouldPrintDeclaration(Declaration decl) { shouldDumpDeclaration(decl) }
+}

cpp/ql/test/library-tests/ir/no-function-calls/PrintConfig.qll

@@ -0,0 +1,24 @@
+private import cpp
+
+/**
+ * Holds if the specified location is in standard headers.
+ */
+predicate locationIsInStandardHeaders(Location loc) {
+  loc.getFile().getAbsolutePath().regexpMatch(".*/include/[^/]+")
+}
+
+/**
+ * Holds if the AST or IR for the specified declaration should be printed in the test output.
+ *
+ * This predicate excludes declarations defined in standard headers.
+ */
+predicate shouldDumpDeclaration(Declaration decl) {
+  not locationIsInStandardHeaders(decl.getLocation()) and
+  (
+    decl instanceof Function
+    or
+    decl.(GlobalOrNamespaceVariable).hasInitializer()
+    or
+    decl.(StaticLocalVariable).hasInitializer()
+  )
+}

cpp/ql/test/library-tests/ir/no-function-calls/aliased_ir.expected

@@ -0,0 +1,38 @@
+test.cpp:
+#    5| void foo(int*)
+#    5|   Block 0
+#    5|     v5_1(void)           = EnterFunction                    : 
+#    5|     m5_2(unknown)        = AliasedDefinition                : 
+#    5|     m5_3(unknown)        = InitializeNonLocal               : 
+#    5|     m5_4(unknown)        = Chi                              : total:m5_2, partial:m5_3
+#    5|     r5_5(glval<int *>)   = VariableAddress[x]               : 
+#    5|     m5_6(int *)          = InitializeParameter[x]           : &:r5_5
+#    5|     r5_7(int *)          = Load[x]                          : &:r5_5, m5_6
+#    5|     m5_8(unknown)        = InitializeIndirection[x]         : &:r5_7
+#    5|     m5_9(unknown)        = Chi                              : total:m5_4, partial:m5_8
+#    6|     r6_1(glval<unknown>) = FunctionAddress[operator delete] : 
+#    6|     r6_2(glval<int *>)   = VariableAddress[x]               : 
+#    6|     r6_3(int *)          = Load[x]                          : &:r6_2, m5_6
+#    6|     v6_4(void)           = Call[operator delete]            : func:r6_1, 0:r6_3
+#    6|     m6_5(unknown)        = ^CallSideEffect                  : ~m5_9
+#    6|     m6_6(unknown)        = Chi                              : total:m5_9, partial:m6_5
+#    7|     v7_1(void)           = NoOp                             : 
+#    5|     v5_10(void)          = ReturnIndirection[x]             : &:r5_7, ~m6_6
+#    5|     v5_11(void)          = ReturnVoid                       : 
+#    5|     v5_12(void)          = AliasedUse                       : ~m6_6
+#    5|     v5_13(void)          = ExitFunction                     : 
+
+#   11| void jazz()
+#   11|   Block 0
+#   11|     v11_1(void)           = EnterFunction        : 
+#   11|     m11_2(unknown)        = AliasedDefinition    : 
+#   11|     m11_3(unknown)        = InitializeNonLocal   : 
+#   11|     m11_4(unknown)        = Chi                  : total:m11_2, partial:m11_3
+#   12|     r12_1(glval<unknown>) = FunctionAddress[bar] : 
+#   12|     v12_2(void)           = Call[bar]            : func:r12_1
+#   12|     m12_3(unknown)        = ^CallSideEffect      : ~m11_4
+#   12|     m12_4(unknown)        = Chi                  : total:m11_4, partial:m12_3
+#   13|     v13_1(void)           = NoOp                 : 
+#   11|     v11_5(void)           = ReturnVoid           : 
+#   11|     v11_6(void)           = AliasedUse           : ~m12_4
+#   11|     v11_7(void)           = ExitFunction         : 

cpp/ql/test/library-tests/ir/no-function-calls/aliased_ir.ql

@@ -0,0 +1,11 @@
+/**
+ * @kind graph
+ */
+
+private import cpp
+private import semmle.code.cpp.ir.implementation.aliased_ssa.PrintIR
+private import PrintConfig
+
+private class PrintConfig extends PrintIRConfiguration {
+  override predicate shouldPrintDeclaration(Declaration decl) { shouldDumpDeclaration(decl) }
+}

cpp/ql/test/library-tests/ir/no-function-calls/test.cpp

@@ -0,0 +1,13 @@
+// Test for edge case, where we have a database without any function calls or
+// where none of the function calls have any arguments, but where we do have
+// a delete expression.
+
+void foo(int* x) {
+  delete x;
+}
+
+void bar();
+
+void jazz() {
+  bar();
+}