Version: 3.1.2
tls.h File Reference


#define wxTLS_TYPE(type)   compiler-dependent-implementation
 Macro to be used for thread-specific variables declarations. More...
#define wxTLS_VALUE(var)
 Macro to access thread-specific variables. More...
#define wxTLS_PTR(var)
 Macro to return address of a thread-specific variables. More...

Macro Definition Documentation

#define wxTLS_PTR (   var)

Macro to return address of a thread-specific variables.

This macro is similar to wxTLS_VALUE() except that it always returns a pointer to the type of thread-specific variable.

Notice that this is not a constant expression even if the macro is defined simply as &var – the value returned is still different for every thread.

#define wxTLS_TYPE (   type)    compiler-dependent-implementation

Macro to be used for thread-specific variables declarations.

This macro can be used to define thread-specific variables of the specified type. Such variables must be global or static and must be POD, i.e. not have any constructors or destructor (even implicitly generated by the compiler due to use of base classes or members which are not POD in a struct).

Example of use:

1 struct PerThreadData
2 {
3  ... data which will be different for every thread ...
4 };
6 static wxTLS_TYPE(PerThreadData) s_threadDataVar;
7 #define s_threadData (wxTLS_VALUE(s_threadDataVar))
9 ... use s_threadData as a variable of type PerThreadData ...

Notice that the use of the ugly wxTLS_VALUE() macro is unfortunately required if you need to support platforms without native compiler support for thread-specific variables. If you compile your code only on platforms which do have such support (recent versions of GNU C++ compiler, Microsoft Visual C++ and Sun C++ compiler are known to have it), you can avoid it and use the variable directly.

#define wxTLS_VALUE (   var)

Macro to access thread-specific variables.

This macro is used to hide the difference in implementation of thread-specific variables under different platforms: they can be of type T used in wxTLS_TYPE() if they are directly supported by the compiler or of type emulating T *, i.e. a pointer to this type otherwise. This macro always returns an expression of type T itself.

As shown in wxTLS_TYPE() example, you may want to #define a symbol wrapping a thread-specific variable with this macro. And, as also explained in wxTLS_TYPE() documentation, you may avoid using it entirely if you target only recent compilers.

See also