c/c++程序中的print(而不是printf())由编译器的哪一部分检测

Question

Suppose I have written ac program and I have written print instead of printf .
Now my question is which part of compiler will detect this ?

Answer 1

I'm assuming OP means which part of the compiler internally , such as the lexer, parser, type analyzer, name analyzer, code generator, etc.

Without knowing specifically about gcc/llvm, I would assume that it's the Name Analyzer (more specifically, this is a part of the "Semantic Analyzer" generally, which also does Type Analysis), as that wouldn't be able to match "print" to anything that exists name wise. This is the same thing that prevents things such as:

x = 5;

When x does not exist previously.

Answer 2

Strictly speaking, assume that print will be represented by token in the form:

{ token type = Identifier, token value = 'print' }

This transformation from source characters in tokens is done by lexical analyzer. Lets say you have function get_token , it reads source file characters and returns token (in the form of above structure). We can say that source file is viewed as a sequence of such tokens.

To do higher-level job we call lower-level routines, so assume now that you have function parse_declaration that uses get_token . parse_declaration is responsible to recognize declaration in your program (it is done using parsing algorithm, eg recursive descent ) If declaration is recognized it will save token value in symbol table, with type information and attributes.

Now, assume you have function parse_expression , it will call get_token , and if token type is Identifier it will perform name lookup . This means that it will search for token value in the symbol table. If search is unsuccessful it will print error message (something like "token value : undeclared identifier" ).

Of course this concept is simplified. In practice there is rather sophisticated logic for lexical analysis, parsing, semantics (how language 'behaves', name lookup is part of language semantics), and this logic should be as independent (separate) on one another as possible.