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.
According to C11, Section 6.3.2.3, para. 7 of the C standard [ISO/IEC 9899:2011], states:
A pointer to an object or incomplete type may be converted to a pointer to a different object or incomplete type. If the resulting pointer is not correctly aligned for the pointed-to type, the behavior is undefined.
...
Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 94 S | Fully implemented | |||||||
| GCC |
| Can detect some violations of this rule when the | |||||||
| EDG | |||||||||
| Compass/ROSE | Can detect violations of this rule. However, it does not flag explicit casts to | ||||||||
| castexpr | Fully implemented. |
Noncompliant Code Example
For objects declared on the stack, The the C Standard standard [ISO/IEC 9899:2011] provides alignas to declare an object to have a stricter alignment. This It can be used to resolve the following noncompliant code example.
...
CERT C++ Secure Coding Standard: EXP36-CPP. Do not convert pointers into more strictly aligned pointer types
ISO/IEC 9899:2011 Section Section 6.2.5, "Types"
ISO/IEC TR 17961 (Draft) Converting pointer values to more strictly aligned pointer types [alignconv]
...