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GCC gives a -Wignored-attributes warning when a class template is instantiated with a type that has an aligned(n) attribute. Specifically, cris-elf uses 'typedef int __attribute_((__aligned(4))) _Atomic_word;' and so compiling libstdc++ headers gives: warning: ignoring attributes on template argument ‘int’ [-Wignored-attributes] This commit reduces four occurrences of make_unsigned<_Atomic_word> into two, one in bits/shared_ptr_base.h and one in ext/atomicity.h, and uses diagnostic pragmas around the two remaining uses to avoid the warnings. Because the unsigned type might have lost the alignment of _Atomic_word that is needed for atomic ops (at least on cris-elf), the unsigned type should only be used for plain non-atomic arithmetic. To prevent misuse, it's defined as a private type in _Sp_counted_base, and is defined and then undefined as a macro in ext/atomicity.h, so that it's not usable after __exchange_and_add_single and __atomic_add_single have been defined. We also get a warning from instantiating __int_traits<_Atomic_word> in shared_ptr_base.h which can be avoided by calculating the maximum signed value from the maximum unsigned value. libstdc++-v3/ChangeLog: PR libstdc++/122172 * include/bits/shared_ptr_base.h (_Sp_counted_base): Define _Unsigned_count_type for make_unsigned<_Atomic_word>. Replace __int_traits<_Atomic_word> with equivalent expression. * include/ext/atomicity.h (_GLIBCXX_UNSIGNED_ATOMIC_WORD): Define macro for unsigned type to use for arithmetic. (__exchange_and_add_single, __atomic_add_single): Use it. Reviewed-by: Hans-Peter Nilsson <hp@axis.com>