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Should x represent a hardware register or some other memory-mapped device that has side effects when accessed, the previous miscompiled code example may produce unexpected behavior.

Compliant Solution

Eide and Regehr tested a workaround by wrapping volatile accesses with function calls. They describe it with the intuition that "we can replace an action that compilers empirically get wrong by a different action—a function call—that compilers can get right" [Eide and Regehr]. For example, the workaround for the noncompliant code example would be

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The workarounds proposed by Eide and Regehr fix many of the volatile-access bugs in the tested compilers. However, compilers are always changing, so critical sections of code should be compiled as if for deployment, and the compiled object code should be inspected for the correct behavior.

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The volatile qualifier should be used with caution in mission-critical situations. Always make sure code that assumes certain behavior when using the volatile qualifier is inspected at the object code level for compiler bugs.

Automated Detection

Bibliography

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