[#BloombergLP-bdlma-GuardingAllocator]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlma.adoc[bdlma]::GuardingAllocator
:relfileprefix: ../../
:mrdocs:

Concrete thread‐safe guarding allocator that adjoins a protected guard page to each allocated block.

== Synopsis

Declared in `<bdlma_guardingallocator.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
class GuardingAllocator
    : public xref:BloombergLP/bslma/Allocator.adoc[bslma::Allocator]
----

== Description

This class defines a concrete thread‐safe "guarding" allocator mechanism that implements the `bslma::Allocator` protocol, and adjoins a read/write protected guard page to each block of memory returned by the `allocate` method. The guard page is placed immediately before or immediately following the block returned from `allocate` according to the `GuardPageLocation` enumerator value (optionally) supplied at construction. Note that, unlike many other allocators, an allocator cannot be (optionally) supplied at construction; instead, a system facility is used that allocates blocks of memory in multiples of the system page size. Also note that this allocator is intended for debugging purposes _only_.

== Base Classes

[cols="1,4"]
|===
| Name| Description
| `xref:BloombergLP/bslma/Allocator.adoc[bslma::Allocator]`
| Pure abstract protocol for clients and suppliers of raw memory.
|===

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/Allocator/size_type.adoc[`size_type`] 
| Alias for an unsigned integral type capable of representing the number of bytes in this platform's virtual address space.
|===


== Enums

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlma/GuardingAllocator/GuardPageLocation.adoc[`GuardPageLocation`] 
| Enumerate the configuration options for `GuardingAllocator` that may be (optionally) supplied at construction.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlma/GuardingAllocator/2constructor.adoc[`GuardingAllocator`]         [.small]#[constructor]#
| Create a guarding allocator.
| xref:BloombergLP/bdlma/GuardingAllocator/2destructor.adoc[`~GuardingAllocator`] [.small]#[destructor]# [.small]#[virtual]#
| Destroy this allocator object. Note that destroying this allocator has no effect on any outstanding allocated memory.
| xref:BloombergLP/bslma/Allocator/operator_assign.adoc[`operator=`] 
| 
| xref:BloombergLP/bdlma/GuardingAllocator/allocate-07.adoc[`allocate`] 
| `allocate` overloads
| xref:BloombergLP/bdlma/GuardingAllocator/deallocate-03.adoc[`deallocate`] 
| Return the memory block at the specified `address` back to this allocator.
| xref:BloombergLP/bslma/Allocator/deleteObject-09.adoc[`deleteObject`] 
| `deleteObject` overloads
| xref:BloombergLP/bslma/Allocator/deleteObjectRaw-06f.adoc[`deleteObjectRaw`] 
| `deleteObjectRaw` overloads
| xref:BloombergLP/bslma/Allocator/is_equal.adoc[`is_equal`] 
| 
|===


== Static Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/Allocator/throwBadAlloc.adoc[`throwBadAlloc`] 
| Throw `std::bad_alloc` or abort the program.
|===


== Protected Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bslma/Allocator/do_allocate.adoc[`do_allocate`]  [.small]#[virtual]#
| Return a newly allocated block of at least `bytes` with `alignment`.
| xref:BloombergLP/bslma/Allocator/do_deallocate.adoc[`do_deallocate`]  [.small]#[virtual]#
| Return the memory block at `p` having `bytes` and `alignment`.
| xref:BloombergLP/bslma/Allocator/do_is_equal.adoc[`do_is_equal`]  [.small]#[virtual]#
| Return whether this allocator can exchange memory with `other`.
|===



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