CmdStan executables and utility programs use streams standard output (stdout) and standard error (stderr) to report information and error messages, respectively.
All program executables provide a return code between 0 and 255:
0 - Program ran to termination as expected.
value in range [1 : 125] - Method invoked could not run due to problems with model or data.
value > 128 - Fatal error during execution, process terminated by signal. The signal number is retcode - 128.
Common sources of program error are:
Missing or ill-formed input data. All variables declared in the data block must be supplied in the input data file.
Model parameters cannot be initialized due to model misspecification.
Indexing errors. The Stan language provides indexing and slicing operations. Indexing errors are easy to make and difficult to debug. The compiler and runtime detect index out of bounds errors; they cannot detect the semantic errors such as indexing into the wrong variables or incorrect index updates.