You can use SPDLOG_VERSION to select the latest spdlog features
where available while falling back to older implementations otherwise.
Using SPDLOG_TO_VERSION() for the value to compare with is recommended.
for Example:
```c++
void sink_it_(const details::log_msg &msg) override
{
#if SPDLOG_VERSION < SPDLOG_TO_VERSION(1,4,0)
fmt::memory_buffer formatted;
#else
memory_buf_t formatted;
#endif
sinks::base_sink<Mutex>::formatter_->format(msg, formatted);
// bala bala...
}
```
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