c++ - Boolean in ifdef: is "#ifdef A && B" the same as "#if defined(A) && defined(B)"?

Question

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

In C++, is this:

#ifdef A && B

the same as:

#if defined(A) && defined(B)

?

I was thinking it wasn't, but I haven't been able to find a difference with my compiler (VS2005).

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1 Answer

深蓝 · Answer 1 · 2021-10-23T18:29:30+0000

They are not the same. The first one doesn't work (I tested in gcc 4.4.1). Error message was:

test.cc:1:15: warning: extra tokens at end of #ifdef directive

If you want to check if multiple things are defined, use the second one.