Question

I am learning about compilers and am trying to understand what goes on in the separate phases. The questions I have are dealing with a 2-phase compiler. So, the front-end and the back-end. In the front-end is where we have the lexical analysis, syntax analysis, and semantic analysis. In the back-end is where we have instruction selection, register allocation, and instruction scheduling.

I am given some situations that produce errors and told to determine if the error could be detected by a compiler and in which phase it occurs.

A statement in an Ada program is missing the terminating semicolon. I know this would be detected in the front-end, but I'm not sure if it would be deteced by the lexical analyzer, syntax analyzer, or semantic analyzer. The lexical analyzer goes through each line character by character and separates them into tokens. So for something like "x = y + 1;" the tokens are <x>, <=>, <y>, <+>, <1>, <;>. So if the semicolon was mission, would the lexical analyzer get to the end of the line and detect that there is no semicolon and raise the error? Or would something like "x = x + 1" be detected by the syntax analyzer. The syntax analyzer checks to see if the programs structure is legal for the language we are compiling. In this case, since we are missing the semicolon, it wouldn't be legal, would it? I could also see how this would be detected by the semantic analyzer too though. My problem is determining which one it is. Any help would be appreciated.