get library, function and reason codes
for OpenSSL errors
The error code returned by
ERR_get_error(3) consists of a library number, function code,
and reason code.
can be used to extract these.
The library number and function code describe where the error occurred, whereas the reason code is the information about what went wrong.
Each sub-library of OpenSSL has a unique library number; function and reason codes are unique within each sub-library. Note that different libraries may use the same value to signal different functions and reasons.
ERR_R_* reason codes such as
ERR_R_MALLOC_FAILURE are globally unique. However,
when checking for sub-library specific reason codes, be sure to also compare
the library number.
indicates whether a given error code is a fatal error.
These functions are implemented as macros.
ERR_GET_REASON() return the library number, function
code, and reason code, respectively.
ERR_FATAL_ERROR() returns non-zero if the
error is fatal or 0 otherwise.
ERR_FATAL_ERROR() first appeared in SSLeay 0.4.4 and
have been available since OpenBSD 2.4.