Re: [libvirt] [PATCH 1/3] Preserve errno across calls to error reporting functions

There are cases when we want log an error message while still preserving errno for a caller, but the functions that log errors make system calls that will clear errno. This patch preserves errno during those most basic error logging functions (corresponding to virReportSystemError(), virReportOOMError(), networkReportError(), etc, as well as virStrError()). It does *not preserve errno across calls to higher level items such as virDispatchError(), as it's assumed the caller is all finished with any need for errno by the time it dispatches the error.

const char *virStrerror(int theerrno, char *errBuf, size_t errBufLen) { + int save_errno = errno; + const char *ret; + #ifdef HAVE_STRERROR_R # ifdef __USE_GNU /* Annoying linux specific API contract */ - return strerror_r(theerrno, errBuf, errBufLen); + ret = strerror_r(theerrno, errBuf, errBufLen); # else strerror_r(theerrno, errBuf, errBufLen); - return errBuf; + ret = errBuf; # endif #else /* Mingw lacks strerror_r and its strerror is definitely not