Opposite of C preprocessor “stringification”

问题:

When using C preprocessor one can stringify macro argument like this:

#define TO_STRING(x) "a string with " #x

and so when used, the result is as follows:

TO_STRING(test) will expand to: "a string with test"

Is there any way to do the opposite? Get a string literal as an input argument and produce a C identifier? For example:

TO_IDENTIFIER("some_identifier") would expand to: some_identifier

Thank you for your answers.

EDIT: For those wondering what do I need it for:

I wanted to refer to nodes in a scene graph of my 3D engine by string identifiers but at the same time avoid comparing strings in tight loops. So I figured I'll write a simple tool that will run in pre-build step of compilation and search for predefined string - for example ID("something"). Then for every such token it would calculate CRC32 of the string between the parenthesis and generate a header file with #defines containing those numerical identifiers. For example for the string "something" it would be:

#define __CRC32ID_something 0x09DA31FB

Then, generated header file would be included by each cpp file using ID(x) macros. The ID("something") would of course expand to __CRC32ID_something, so in effect what the compiler would see are simple integer identifiers instead of human friendly strings. Of course now I'll simply settle for ID(something) but I thought that using quotes would make more sense - a programmer who doesn't know how the ID macro works can think that something without quotes is a C identifier when in reality such identifier doesn't exist at all.

回答1:

No, you can't unstringify something.

回答2:

//unstringify test

enum fruits{apple,pear};

#define IF_WS_COMPARE_SET_ENUM(x) if(ws.compare(L#x)==0)f_ret=x;

fruits enum_from_string(wstring ws)
{
 fruits f_ret;
 IF_WS_COMPARE_SET_ENUM(apple)
 IF_WS_COMPARE_SET_ENUM(pear)
 return f_ret;
}

void main()
{
 fruits f;
 f=enum_from_string(L"apple");
 f=enum_from_string(L"pear");
}