An object that has volatile-qualified type may be modified in ways unknown to the implementation or have other unknown side effects. It is possible to reference a volatile object by using a non-volatile value, but the resulting behavior is undefined. According to C99 Section 6.7.3, "Type qualifiers," Paragraph 5:
If an attempt is made to refer to an object defined with a volatile-qualified type through use of an lvalue with non-volatile-qualified type, the behavior is undefined.
This also applies to objects that behave as if they were defined with qualified types, such as an object at a memory-mapped input/output address.
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Risk Assessment
Accessing a volatile object through a non-volatile reference results in undefined behavior.
Rule |
Severity |
Likelihood |
Remediation Cost |
Priority |
Level |
|---|---|---|---|---|---|
EXP32-C |
1 (low) |
3 (unlikely) |
2 (medium) |
P6 |
L2 |
References
[[ISO/IEC 9899-1999]] Section 6.7.3, "Type qualifiers," and Section 6.5.16.1, "Simple assignment"