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Do not convert convert a pointer value to a pointer type that is more strictly aligned than the referenced type. Different  Different alignments are possible for different types of objects. If the type-checking system is overridden by an explicit cast or the pointer is converted to a void pointer (void *) and then to a different type, the alignment of an object may be changed.

The C Standard, 6.3.2.3, paragraph 7 [ISO/IEC 9899:2011], states:

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In this noncompliant example, the char pointer  pointer &c is  is converted to the more strictly aligned int pointer  pointer ip. On some implementations, cp will  will not match &c. As a result, if a pointer to one object type is converted to a pointer to a different object type, the second object type must not require stricter alignment than the first.

#include <assert.h>
 
void func(void) {
  char c = 'x';
  int *ip = (int *)&c; /* This can lose information */
  char *cp = (char *)ip;

  /* Will fail on some conforming implementations */
  assert(cp == &c);
}

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In this compliant solution, the char value  value is stored into an object of type int so  so that the pointer's value will be properly aligned:

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Related Guidelines

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