What is the best way to know if a value is defined in an enum?

Question

I read that it is difficult to find out if an element is in an enumeration. So what would be the best way ?

For example, the following code comes from the Linux kernel 2.6.32:

enum v4l2_colorfx { V4L2_COLORFX_NONE = 0, V4L2_COLORFX_BW = 1, V4L2_COLORFX_SEPIA = 2, };

And this one from the 2.6.38 version:

enum v4l2_colorfx { V4L2_COLORFX_NONE = 0, V4L2_COLORFX_BW = 1, V4L2_COLORFX_SEPIA = 2, V4L2_COLORFX_NEGATIVE = 3, V4L2_COLORFX_EMBOSS = 4, V4L2_COLORFX_SKETCH = 5, V4L2_COLORFX_SKY_BLUE = 6, V4L2_COLORFX_GRASS_GREEN = 7, V4L2_COLORFX_SKIN_WHITEN = 8, V4L2_COLORFX_VIVID = 9, };

How would you check if V4L2_COLORFX_NEGATIVE is defined ? Would #ifndef V4L2_COLORFX_NEGATIVE be okay ?

Joe · Accepted Answer · 2011-10-14 06:14:12Z

You would have to look at a compiler macro in the wider context (for example the version of linux, I don't know what's available) or some other piece of information at compile time. ifndef is for checking if compiler macros are defined, not symbols in code.

crazyjul · Accepted Answer · 2011-10-14 06:22:12Z

Check the version of linux in /usr/include/linux/version.h ( you need to install kernel headers though )

it contains something like :

#define LINUX_VERSION_CODE 132640 #define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))

So you can use this :

#if LINUX_VERSION_CODE >= KERNEL_VERSION( 2, 6, 38 )

Collectives™ on Stack Overflow

What is the best way to know if a value is defined in an enum?

2 Answers 2

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Related