# Potential Incompatibilities with Earlier Versions

This section describes incompatibilities introduced by particular versions of SIP. Normally these are the removal of previously deprecated features.

## SIP v4.16

Prior to this version, if no valid version tag was specified using the `-t` command line option to sip then all versions of the corresponding timeline were considered disabled.

Starting with this version SIP assumes that the latest version is enabled if no valid version tag was specified. Exactly what is meant by the latest version can be changed by using the `-B` command line option to define a backstop for a timeline. See the `%Timeline` directive for more details.

## SIP v4.14.4

Prior to this version, the handwritten code defined by the `%VirtualErrorHandler` directive was called without the Python Global Interpreter Lock (GIL) being held and from an arbitrary thread.

Starting with this version the code is called with the GIL being held and from the thread that raised the error. In addition the code is provided a value called `sipGILState` that may be passed to `SIP_RELEASE_GIL()` in order to release the GIL. This must be done if the code changes the execution path (e.g. by throwing a C++ exception).

## SIP v4.12.3

Prior to this version, when SIP searches a class hierachy to see if there is a Python reimplementation of a virtual C++ method, it ignored any objects that were not Python functions or methods.

Starting with this version such an object is not ignored and will be called. If it is not callable then a Python exception will be raised. For example, the following code will now raise an excepton because the `Mixin.event` attribute will now be called as it is assumed to be a valid reimplementation of `QObject.event()`:

    class Mixin:
        event = False

    class MyObject(QObject, Mixin):
        pass

## SIP v4.12

Prior to this version several directives ignored any enclosing `%If` directive. Starting with this version all directives are affected by the `%If` directive.

## SIP v4.10.1

### Newly Deprecated Features

The following parts of the C API are now deprecated (but still supported).

- The `D` format character of `sipParseResult()`.

## SIP v4.8

### __truediv__

Prior to this version the `__div__()` special method implicitly defined the `__truediv__()` special method. From this version the `__truediv__()` special method must be explicitly defined.

### sipWrapper user Member

Prior to this version the `sipWrapper` structure had a member called `user` which is available for handwritten code to use. From this version `user` is a member of the `sipSimpleWrapper` structure.

`sipWrapper` pointers can be safely cast to `sipSimpleWrapper` pointers, so if your code does something like:

    ((sipWrapper *)obj)->user = an_object_reference;

then you just need to change it to:

    ((sipSimpleWrapper *)obj)->user = an_object_reference;

### Removal of Previously Deprecated Features

The following parts of the C API have been removed.

- The `a`, `A`, `M`, `N`, `O`, `P` and `T` format characters from `sipBuildResult()` and `sipCallMethod()`.
- The `a`, `A`, `L` and `M` format characters from `sipParseResult()`.
- `sipConvertToCpp()`
- `sipIsSubClassInstance()`
- `sipTransfer()`
- The `transfer()` function of the `sip` module.
- The old-style generated type convertors.

In addition the `-a` command line option to `configure.py` has been removed.

### Removal of PyQt-specific Features

The following PyQt-specific support functions have been removed.

- `sipConnectRx()`
- `sipDisconnectRx()`
- `sipEmitSlot()`
- `sipGetSender()`

### Newly Deprecated Features

The following parts of the C API are now deprecated (but still supported).

- The Generated Type Objects.
- The Generated Named Enum Type Objects.
- `sipConvertFromInstance()`
- `sipConvertFromMappedType()`
- `sipConvertFromNamedEnum()`
- `sipConvertFromNewInstance()`
- `sipCanConvertToInstance()`
- `sipCanConvertToMappedType()`
- `sipConvertToInstance()`
- `sipConvertToMappedType()`
- `sipForceConvertToInstance()`
- `sipForceConvertToMappedType()`
- `sipClassName()`
- `sipFindClass()`
- `sipFindNamedEnum()`
- `sipFindMappedType()`
- `sipGetWrapper()`
- `sipReleaseInstance()`
- `sipReleaseMappedType()`
- `sipWrapper_Check()`
- The `B`, `C` and `E` format characters of `sipBuildResult()` and `sipCallMethod()`.
- The `s`, `C` and `E` format characters of `sipParseResult()`.

## SIP v4.7.8

### Automatic int to Enum Conversions

This version allows a Python `int` object to be passed whenever an enum is expected. This can mean that two signatures that were different with prior versions are now the same as far as Python is concerned.

The `Constrained` argument annotation can now be applied to an enum argument to revert to the earlier behaviour.

## SIP v4.7.3

### Complementary Comparison Operators

Prior to this version SIP did not automatically generate missing complementary comparison operators. Typically this was worked around by adding them explicitly to the .sip files, even though they weren’t implemented in C++ and relied on the C++ compiler calling the complementary operator that was implemented.

A necessary change to the code generator meant that this not longer worked and so SIP was changed to automatically generate any missing complementary operators. If you have added such operators explicitly then you should remove them or make them dependent on the particular version of SIP.

## SIP v4.4

### %ConvertFromTypeCode and %ConvertToTypeCode

Handwritten `%ConvertFromTypeCode` and `%ConvertToTypeCode` now have the responsibility for implementing the `Transfer` and `TransferBack` annotations.

### SIP_BUILD

The `SIP_BUILD` C preprocessor symbol has been removed.

### Newly Deprecated Features

The following parts of the C API are now deprecated (but still supported).

- The old-style generated type convertors.
- `sipConvertToCpp()`
- `sipIsSubClassInstance()`