Formats a string according to
format and prefix it to an existing
error message. If
NULL (ie: no error variable) then do nothing.
NULL (ie: an error variable is present but there is no
error condition) then also do nothing.
Available since: 2.16
This function is not directly available to language bindings.
A return location for a
The argument will be modified by the function. The argument can be set to
NULLby the function.
The argument can be
The caller of the function takes ownership of the data, and is responsible for freeing it.
Printf()-style format string.
The data is owned by the caller of the function. The value is a NUL terminated UTF-8 string.