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The compliant solution disables the nonconforming declaration of strerror_r() by explicitly requesting POSIX conformance before including the <string.h> header that declares the function and handles the function's failure by copying the "Unknown error" string into the buffer. An alternate solution is to use the strerror_s() function defined by Annex K.
Note that the function assigns the result of the call to strerror_r() to a variable of type int. This assignment is a defense-in-depth strategy guarding against inadvertently invoking strerror_r() that returns char*: a conforming compiler is required to issue a diagnostic for the ill-formed conversion from char* to int.
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