[#bsl-basic_syncbuf-pbackfail]
= xref:bsl.adoc[bsl]::xref:bsl/basic_syncbuf.adoc[basic&lowbar;syncbuf]::pbackfail
:relfileprefix: ../../
:mrdocs:

Tries to back up the input sequence&period;

== Synopsis

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

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
virtual
int&lowbar;type
pbackfail(int&lowbar;type &lowbar;&lowbar;c = traits&lowbar;type&colon;&colon;eof());
----

== Description

[NOTE]
====
Base class version does nothing, returns eof()&period;

====

== Return Value

eof() on failure, _some other value_ on success

== Parameters

[cols="1,4"]
|===
| Name| Description
| *&lowbar;&lowbar;c*
| The character to be inserted back into the sequence&period;
|===

== Postconditions

* The constraints of `gptr(),` `eback(),` and `pptr()` are the same as for `underflow()&period;`


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