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LibCore: Define and use a fallible, OS-independent getgrent(_r) wrapper
Rather than maintaining a list of #ifdef guards to check systems that do not provide the reentrant version of getgrent, we can use C++ concepts to let the compiler perform this check for us. While we're at it, we can also provide this wrapper as fallible to let the caller TRY calling it.
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1ee808fae6
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3 changed files with 61 additions and 31 deletions
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@ -86,6 +86,40 @@ static ErrorOr<Optional<struct passwd>> getpwent_impl(Span<char> buffer)
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return Optional<struct passwd> {};
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}
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// clang-format off
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template<typename T>
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concept SupportsReentrantGetgrent = requires(T group, T* ptr)
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{
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getgrent_r(&group, nullptr, 0, &ptr);
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};
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// clang-format on
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// Note: This has to be in the global namespace for the extern declaration to trick the compiler
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// into finding a declaration of getgrent_r when it doesn't actually exist.
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static ErrorOr<Optional<struct group>> getgrent_impl(Span<char> buffer)
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{
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if constexpr (SupportsReentrantGetgrent<struct group>) {
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struct group group;
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struct group* ptr = nullptr;
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extern int getgrent_r(struct group*, char*, size_t, struct group**);
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auto result = getgrent_r(&group, buffer.data(), buffer.size(), &ptr);
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if (result == 0 && ptr)
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return group;
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if (result != 0 && result != ENOENT)
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return Error::from_errno(result);
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} else {
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errno = 0;
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if (auto const* group = ::getgrent())
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return *group;
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if (errno)
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return Error::from_errno(errno);
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}
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return Optional<struct group> {};
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}
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namespace Core::System {
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#ifndef HOST_NAME_MAX
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@ -676,6 +710,11 @@ ErrorOr<Optional<struct passwd>> getpwuid(uid_t uid)
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return Optional<struct passwd> {};
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}
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ErrorOr<Optional<struct group>> getgrent(Span<char> buffer)
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{
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return getgrent_impl(buffer);
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}
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ErrorOr<Optional<struct group>> getgrgid(gid_t gid)
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{
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errno = 0;
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