I have reading the source code, specifically in the objective directory: xgboost/src/objective at master · dmlc/xgboost (github.com)
There are files and classes for regression, ranking, and multiclass classification tasks. For example the regression_obj.cu file has a RegLossObj class in it and the multiclass_obj.cu file has the SoftmaxMultiClassObj class in it (which inherits from ObjFunction). However, I cannot find a module or class structure for normal binary classification task. Would the SoftmaxMultiClassObj class just be reduced to binary classification with only two classes?