[#BloombergLP-bdlde-Utf8CheckingInStreamBufWrapper-pbackfail]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlde.adoc[bdlde]::xref:BloombergLP/bdlde/Utf8CheckingInStreamBufWrapper.adoc[Utf8CheckingInStreamBufWrapper]::pbackfail
:relfileprefix: ../../../
:mrdocs:

Back up input one byte&period; Return the byte at the new position, or `eof` with the state of this object unchanged on failure&period; If the optionally specified `c` is not `eof`, substitute `c` for the previous byte and return that value&period; If `c` is `eof`, do not substitute it for the previous byte and return the byte was there, or if the previous byte is unknown, fail&period; If values of `c` that are not `eof` are specified, this function will succeed for at least 8 successive calls, possibly many more times&period; The behavior is undefined unless `c` is either `eof` or a value representable as a `char&lowbar;type`&period; Note that this is forwarded to with a `char&lowbar;type` passed to `c` by the public method `sputbackc` in the base class, and called with `eof` passed to `c` by the public method `sungetc` in the base class&period;

== Synopsis

Declared in `&lt;bdlde&lowbar;utf8checkinginstreambufwrapper&period;h&gt;`

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


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