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cc-preprocessorconditional-compilation

Need help in understand C code

Hi I need some help in understand some C code:

#if 0
   some C code 1
#elif 0
   static int8 arry[10];
#pragma Align_to(32, arry)
   ASSERT(((int8ptr_t)arry) & 15) == 0)
#else
   ASSERT(((int8ptr_t)arry) & 15) == 0)
#endif

My questions:

  1. Is only the #else part compiled?

  2. What is the meaning of #pragma Align_to(32, arry) in the #elif 0 case?

Solution

  • Yes, the #else part is what is compiled.

    The #pragma directive is a compiler specific directive. As you compiler was not specified, it could mean anything.

    In your case #pragma Align_to(32, arry), likely tells the compiler to insure variable 'arry' is place in memory on a 32 byte boundary. This is typically for performance reasons or compatibility concerns. You may also want to look into the keyword __attribute__ use to control similar variable attributes.