How to define Max and Min value of CFIndex? - ios

Question

I try to define a macro like this:
#import <CoreFoundation/CFBase.h>
#if __LLP64__
#define CFIndexMax LONG_LONG_MAX;
#define CFIndexMin LONG_LONG_MIN;
#else
#define CFIndexMax LONG_MAX;
#define CFIndexMin LONG_MIN;
#endif
But Xcode always warn me has no define of __LLP64_ which is conditional defined in CFBase.h.

Answer 1

Your problem is that you are checking the value of __LLP64__ but you want to check for the existence of __LLP64__:
#ifdef __LLP64__
#define CFIndexMax LONG_LONG_MAX
#define CFIndexMin LONG_LONG_MIN
#else
#define CFIndexMax LONG_MAX
#define CFIndexMin LONG_MIN
#endif
However, only Windows uses the LLP64 model. Are you planning to build this code on Windows? If not, you should simplify your code by eliminating the conditional.

Answer 2

Actually, the compiler defines __LLP64__ (or more likely __LP64__).
If you take a look at the CFBase.h pre-processor logic again, you'll see it forcibly defines __LLP64__ when compiling for a 64-bit Windows target:
#if defined(__WIN64__) && !defined(__LLP64__)
#define __LLP64__ 1
#endif
Copyright (c) 1998-20016 Apple Inc.
If you're concerned about the size of CGFloat (or even CFIndex types on macOS, take a look at CGBase.h to see how things are defined:
#if defined(__LP64__) && __LP64__
#define CGFLOAT_TYPE double
#define CGFLOAT_IS_DOUBLE 1
#define CGFLOAT_MIN DBL_MIN
#define CGFLOAT_MAX DBL_MAX
#else
#define CGFLOAT_TYPE float
#define CGFLOAT_IS_DOUBLE 0
#define CGFLOAT_MIN FLT_MIN
#define CGFLOAT_MAX FLT_MAX
#endif
Copyright (c) 2000-2011 Apple Inc.
You can conditionally define your max and min CFIndexes based on the boolean value of CGFLOAT_IS_DOUBLE, which is not changing any time soon.
Lastly, I believe Windows is the only OS whose size of long types are 32 bits in a 64-bit runtime (that is, compared to linux and macOS which are 64 bits in a 64-bit runtime).
If you're sure you're switching on the right define, always check if the variable be defined first in the pre-compiler:
#if defined(__LLP64__) & __LLP64__
// conditionally define more stuff
#endif