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Replace preprocessor macro with typedef of the same name

I want to replace the macro with the corresponding type with the same name. I have

#define FooType char*

in a third-party library, and this breaks some of my code (more precisely: some code that I have to use, and which I cannot change myself). I want to replace it with a typedef with the same name, and then #undef with a macro. I tried something like this:

 #define TMP_MACRO FooType #undef FooType typedef TMP_MACRO FooType; #undef TMP_MACRO

But the preprocessor extends this value to:

 typedef FooType FooType;

(at least that's what g++ -E told me). Therefore, the TMP_MACRO macro TMP_MACRO not expand immediately. Since "FooType" does not exist, it does not compile.

How can I replace the FooType macro FooType the correct type and subsequently define the macro? Or is it impossible?

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2 answers

A typedef declaration is usually on the same line, but line numbers mean nothing to the compiler.

 typedef FooType #undef FooType FooType;
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Why not just

 #undef FooType typedef char* FooType

The result you get is correct, since you are instructing the preprocessor to replace TMP_MACRO with FooType (the fact that you undef FooType subsequently means nothing in this regard).

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