[#BSLSTL_OPTIONAL_USES_STD_ALIASES]
= BSLSTL&lowbar;OPTIONAL&lowbar;USES&lowbar;STD&lowbar;ALIASES
:mrdocs:

Macro controlling whether `bsl` optional aliases `std` types&period;

== Synopsis

Declared in `&lt;bslstl&lowbar;optional&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
#define BSLSTL&lowbar;OPTIONAL&lowbar;USES&lowbar;STD&lowbar;ALIASES

----

== Description

The following macro `BSLSTL&lowbar;OPTIONAL&lowbar;USES&lowbar;STD&lowbar;ALIASES` controls whether platform standard library is used as a basis for `bsl` types in the following ways&colon; &hyphen; `bsl&colon;&colon;nullopt` is an alias to `std&colon;&colon;nullopt`

* `bsl&colon;&colon;optional&lt;T&gt;` inherits from `std&colon;&colon;optional&lt;T&gt;` when `T` is not allocator&hyphen;aware&period;

This macro does _not_ control whether there are conversions and comparisons between `std&colon;&colon;optional` and `bsl&colon;&colon;optional`, that is conditioned only on whether `std&colon;&colon;optional` is available (i&period;e&period;, `BSLS&lowbar;LIBRARYFEATURES&lowbar;HAS&lowbar;CPP17&lowbar;BASELINE&lowbar;LIBRARY` is defined)&period;


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