# Improvements to C/C++ analysis

The following changes in version 1.23 affect C/C++ analysis in all applications.

## General improvements

## New queries

| **Query**                   | **Tags**  | **Purpose**                                                        |
|-----------------------------|-----------|--------------------------------------------------------------------|
| Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) | reliability, japanese-era | This query is a combination of two old queries that were identical in purpose but separate as an implementation detail.  This new query replaces Hard-coded Japanese era start date in call (`cpp/japanese-era/constructor-or-method-with-exact-era-date`) and Hard-coded Japanese era start date in struct (`cpp/japanese-era/struct-with-exact-era-date`). |

## Changes to existing queries

| **Query**                  | **Expected impact**    | **Change**                                                       |
|----------------------------|------------------------|------------------------------------------------------------------|
| Query name (`query id`) | Expected impact | Message. |
| Hard-coded Japanese era start date in call (`cpp/japanese-era/constructor-or-method-with-exact-era-date`) | Deprecated | This query has been deprecated.  Use the new combined query Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) instead. |
| Hard-coded Japanese era start date in struct (`cpp/japanese-era/struct-with-exact-era-date`) | Deprecated | This query has been deprecated.  Use the new combined query Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) instead. |
| Hard-coded Japanese era start date (`cpp/japanese-era/exact-era-date`) | More correct results | This query now checks for the beginning date of the Reiwa era (1st May 2019). |
| Too few arguments to formatting function (`cpp/wrong-number-format-arguments`) | Fewer false positive results | Fixed false positives resulting from mistmatching declarations of a formatting function. |
| Too many arguments to formatting function (`cpp/too-many-format-arguments`) | Fewer false positive results | Fixed false positives resulting from mistmatching declarations of a formatting function. |

## Changes to QL libraries

* The data-flow library has been extended with a new feature to aid debugging.
  Instead of specifying `isSink(Node n) { any() }` on a configuration to
  explore the possible flow from a source, it is recommended to use the new
  `Configuration::hasPartialFlow` predicate, as this gives a more complete
  picture of the partial flow paths from a given source. The feature is
  disabled by default and can be enabled for individual configurations by
  overriding `int explorationLimit()`.
* The data-flow library now allows flow through the address-of operator (`&`).
* The `DataFlow::DefinitionByReferenceNode` class now considers `f(x)` to be a
  definition of `x` when `x` is a variable of pointer type. It no longer
  considers deep paths such as `f(&x.myField)` to be definitions of `x`. These
  changes are in line with the user expectations we've observed.
* There is now a `DataFlow::localExprFlow` predicate and a
  `TaintTracking::localExprTaint` predicate to make it easy to use the most
  common case of local data flow and taint: from one `Expr` to another.
* The member predicates of the `FunctionInput` and `FunctionOutput` classes have been renamed for
  clarity (e.g. `isOutReturnPointer()` to `isReturnValueDeref()`). The existing member predicates
  have been deprecated, and will be removed in a future release. Code that uses the old member
  predicates should be updated to use the corresponding new member predicate.