What worked for me:
Enabling S3 Transfer Acceleration within AWS console
When configuring the client, only utilize the accelerated endpoint service:
clientConfig->endpointOverride = "s3-accelerate.amazonaws.com";
@gabry - your solution was extremely close, I think the reason it wasn't working for me was perhaps due to SDK changes since originally posted as the change is relatively small. Or maybe because I am constructing put object templates for requests used with the transfer manager.
Looking through the logs (Debug level) the SDK automatically concatenates the bucket used in transferManager::UploadFile() with the overridden endpoint. I was getting unresolved host errors as the requested host looked like:
[DEBUG] host: myBucket.myBucket.s3-accelerate.amazonaws.com
This way I could still keep the same S3_BUCKET macro name while only selectively calling this when instantiating a new configuration for upload.
e.g.
<<
...
auto putTemplate = new Aws::S3::Model::PutObjectRequest();
putTemplate->SetStorageClass(STORAGE_CLASS);
transferConfig->putObjectTemplate = *putTemplate;
auto multiTemplate = new Aws::S3::Model::CreateMultipartUploadRequest();
multiTemplate->SetStorageClass(STORAGE_CLASS);
transferConfig->createMultipartUploadTemplate = *multiTemplate;
transferMgr = Aws::Transfer::TransferManager::Create(*transferConfig);
auto transferHandle = transferMgr->UploadFile(localFile, S3_BUCKET, s3File);
transferMgr = Aws::Transfer::TransferManager::Create(*transferConfig);
...
>>