Component bslmf_isvolatile [Package bslmf]

Provide a compile-time check for volatile-qualified types. More...

Classes
struct	bsl::is_volatile< t_TYPE >
struct	bsl::is_volatile< volatile t_TYPE >

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Detailed Description

Outline

• Purpose
• Classes
• Description
  • Usage
    • Example 1: Verify volatile Types

Purpose:

Provide a compile-time check for volatile-qualified types.

Classes:

bsl::is_volatile	meta-function for determining volatile-qualified types
bsl::is_volatile_v	the result value of bsl::is_volatile

See also:

Component bslmf_integralconstant

Description:

This component defines a meta-function, bsl::is_volatile and a template variable bsl::is_volatile_v, that represents the result value of the meta-function, that may be used to query whether a type is volatile-qualified as defined in the C++11 standard [basic.type.qualifier].

bsl::is_volatile meets the requirements of the is_volatile template defined in the C++11 standard [meta.unary.prop].

Note that the template variable is_volatile_v is defined in the C++17 standard as an inline variable. If the current compiler supports the inline variable C++17 compiler feature, bsl::is_volatile_v is defined as an inline constexpr bool variable. Otherwise, if the compiler supports the variable templates C++14 compiler feature, bsl::is_volatile_v is defined as a non-inline constexpr bool variable. See BSLS_COMPILERFEATURES_SUPPORT_INLINE_VARIABLES and BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES macros in bsls_compilerfeatures component for details.

Usage:

In this section we show intended use of this component.

Example 1: Verify volatile Types:

Suppose that we want to assert whether a particular type is volatile-qualified.

First, we create two typedefs -- a volatile-qualified type and an unqualified type:

  typedef int           MyType;
  typedef volatile int  MyVolatileType;

Now, we instantiate the bsl::is_volatile template for each of the typedefs and assert the value static data member of each instantiation:

  assert(false == bsl::is_volatile<MyType>::value);
  assert(true  == bsl::is_volatile<MyVolatileType>::value);

Note that if the current compiler supports the variable templates C++14 feature, then we can re-write the snippet of code above as follows:

  #ifdef BSLS_COMPILERFEATURES_SUPPORT_VARIABLE_TEMPLATES
  assert(false == bsl::is_volatile_v<MyType>);
  assert(true  == bsl::is_volatile_v<MyVolatileType>);
  #endif