https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90370
Bug ID: 90370
Summary: Does 0 correspond to a POSIX errno value for
std::system_category?
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
The C++ standard says in [syserr.errcat.objects]:
"If the argument ev corresponds to a POSIX errno value posv, the function shall
return error_condition(posv, generic_category()). Otherwise, the function shall
return error_condition(ev, system_category()). What constitutes correspondence
for any given operating system is unspecified."
Our current implementation (in src/c++11/system_error.cc) does not consider 0
to correspond to a POSIX errno value. I did that because there is no EXXX macro
defined by POSIX with value zero, as all error numbers are required to be
positive values.
Libc++ and Boost.System do consider 0 to correspond to a POSIX errno value,
meaning "no error" (and Boost even defines the boost::system::errc::success
enumerator with the value zero).
I think both positions can be justified. Zero is not an errno value, but it
does have special meaning.
Should we change our implementation?
