C RELOC_HIDE() Macro Function

This document analyzes the RELOC_HIDE() macro function.

1. Macro

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#define RELOC_HIDE(ptr, off)                    \
  ({ unsigned long __ptr;                       \
    __asm__ ("" : "=r"(__ptr) : "0"(ptr));      \
    (typeof(ptr)) (__ptr + (off)); })

The RELOC_HIDE() macro function calculates the sum of ptr and off passed as parameters. It is used to remove errors that can occur due to compiler optimization techniques. [Code 1] shows the RELOC_HIDE() macro function. Due to the inline assembly on line 3 of [Code 1], the compiler cannot perform optimization. __asm__ ("" : "=r"(__ptr) : "0"(ptr)) is equivalent to __ptr = ptr.

2. References

• http://studyfoss.egloos.com/viewer/5374731