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Unlike earlier versions of the standard, C++11 and later explicitly define a memory location and provide the following note in [intro.memory] paragraph 4 [ISO/IEC 14882-2014]:
[ Note: Thus a bit-field and an adjacent non-bit-field are in separate memory locations, and therefore can be concurrently updated by two threads of execution without interference. The same applies to two bit-fields, if one is declared inside a nested struct declaration and the other is not, or if the two are separated by a zero-length bit-field declaration, or if they are separated by a non-bit-field declaration. It is not safe to concurrently update two bit-fields in the same struct if all fields between them are also bit-fields of non-zero width. – end note ]
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| SEI CERT C Coding Standard | CON32-C. Prevent data races when accessing bit-fields from multiple threads |
Bibliography
| [ISO/IEC 14882-2014] | Subclause 1.7, "The C++ memory model" |
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