CODEWITHSUNDEEP
c-preprocessor
eonil
eonil

Reputation: 86125

How to trigger C-preprocessor error about undefined symbol at #if? (LLVM/CLang/Xcode)

How to trigger C-preprocessor error about missing definition at #if? I'm using LLVM/Clang/Xcode.

This code works.

#define AAAAA 1
#if AAAAA
#endif

And I expected this code will be an error for undefined symbol.

//#define AAAAA 1     Removed definition.
#if AAAAA
#endif

But it did not. Is this standard/regular behavior? And is there other way to triggering preprocessor error?

Upvotes: 3

Views: 2092

Answers (2)

Binks
Binks

Reputation: 1806

If you want to let the compiler check this for you, without rewriting your code, you can use the -Wundef switch as documented here.

In your Xcode project under TARGETS / YourTarget / Build Settings, add -Wundef to "Other Warning Flags" (aka. WARNING_CFLAGS).

Upvotes: 1

JaredPar
JaredPar

Reputation: 755317

It sounds like you want to raise an error if a particular symbol is not defined. If so then just use the #error preprocessor directive

#ifndef AAAAA
#error Some Message
#endif

Upvotes: 2

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