Build failure on nios2 architecture

[ffontaine]

Since version 1.74.0, boost fails to build on nios2:

In file included from libs/atomic/src/lock_pool.cpp:29:
libs/atomic/src/lock_pool.cpp:1029:25: error: static assertion failed: Boost.Atomic unsupported target platform: native atomic operations not implemented for bytes
 BOOST_STATIC_ASSERT_MSG(once_flag_operations::is_always_lock_free, "Boost.Atomic unsupported target platform: native atomic operations not implemented for bytes");
                         ^~~~~~~~~~~~~~~~~~~~

Full build log is available here:
http://autobuild.buildroot.org/results/c03/c03a786791e3aa7801cf1bff9934c4a105f54ce1/build-end.log

[Lastique]

If the build fails then that platform is indeed unsupported. I have no knowledge about nios2, nor have I access to this platform, so I cannot add support for it. PRs are welcome.

Can you provide the output of the g++ -x c++ -dM -E - < /dev/null command on that platform? Add any target-specific options, if needed.

[ffontaine]

It was building fine until version 1.74, I assume that the issue could be linked to the changes made with 76e25f3.

Here is the output of output/host/opt/ext-toolchain/bin/nios2-buildroot-linux-gnu-g++ -x c++ -dM -E - < /dev/null:

#define __DBL_MIN_EXP__ (-1021)
#define __FLT32X_MAX_EXP__ 1024
#define __cpp_attributes 200809
#define __UINT_LEAST16_MAX__ 0xffff
#define __ATOMIC_ACQUIRE 2
#define __FLT_MIN__ 1.1754943508222875e-38F
#define __GCC_IEC_559_COMPLEX 0
#define __cpp_aggregate_nsdmi 201304
#define __UINT_LEAST8_TYPE__ unsigned char
#define __INTMAX_C(c) c ## LL
#define __CHAR_BIT__ 8
#define __UINT8_MAX__ 0xff
#define __WINT_MAX__ 0xffffffffU
#define __FLT32_MIN_EXP__ (-125)
#define __cpp_static_assert 200410
#define nios2_little_endian 1
#define __ORDER_LITTLE_ENDIAN__ 1234
#define __SIZE_MAX__ 0xffffffffU
#define __WCHAR_MAX__ 0x7fffffff
#define __DBL_DENORM_MIN__ double(4.9406564584124654e-324L)
#define __GCC_ATOMIC_CHAR_LOCK_FREE 1
#define __GCC_IEC_559 0
#define __nios2_arch__ 1
#define __FLT32X_DECIMAL_DIG__ 17
#define __FLT_EVAL_METHOD__ 0
#define __unix__ 1
#define __cpp_binary_literals 201304
#define __FLT64_DECIMAL_DIG__ 17
#define __GCC_ATOMIC_CHAR32_T_LOCK_FREE 1
#define __nios2_little_endian__ 1
#define __cpp_variadic_templates 200704
#define __UINT_FAST64_MAX__ 0xffffffffffffffffULL
#define __SIG_ATOMIC_TYPE__ int
#define __DBL_MIN_10_EXP__ (-307)
#define __FINITE_MATH_ONLY__ 0
#define __cpp_variable_templates 201304
#define __GNUC_PATCHLEVEL__ 0
#define __FLT32_HAS_DENORM__ 1
#define __UINT_FAST8_MAX__ 0xff
#define __has_include(STR) __has_include__(STR)
#define __DEC64_MAX_EXP__ 385
#define __INT8_C(c) c
#define __INT_LEAST8_WIDTH__ 8
#define __UINT_LEAST64_MAX__ 0xffffffffffffffffULL
#define __SHRT_MAX__ 0x7fff
#define __LDBL_MAX__ 1.7976931348623157e+308L
#define __UINT_LEAST8_MAX__ 0xff
#define __GCC_ATOMIC_BOOL_LOCK_FREE 1
#define __UINTMAX_TYPE__ long long unsigned int
#define __linux 1
#define __DEC32_EPSILON__ 1E-6DF
#define __FLT_EVAL_METHOD_TS_18661_3__ 0
#define __unix 1
#define __UINT32_MAX__ 0xffffffffU
#define __GXX_EXPERIMENTAL_CXX0X__ 1
#define __LDBL_MAX_EXP__ 1024
#define __WINT_MIN__ 0U
#define __linux__ 1
#define __INT_LEAST16_WIDTH__ 16
#define __SCHAR_MAX__ 0x7f
#define __WCHAR_MIN__ (-__WCHAR_MAX__ - 1)
#define __INT64_C(c) c ## LL
#define __nios2__ 1
#define __DBL_DIG__ 15
#define __GCC_ATOMIC_POINTER_LOCK_FREE 1
#define __SIZEOF_INT__ 4
#define __SIZEOF_POINTER__ 4
#define __GCC_ATOMIC_CHAR16_T_LOCK_FREE 1
#define __USER_LABEL_PREFIX__ 
#define __STDC_HOSTED__ 1
#define __LDBL_HAS_INFINITY__ 1
#define __FLT32_DIG__ 6
#define __FLT_EPSILON__ 1.1920928955078125e-7F
#define __GXX_WEAK__ 1
#define __SHRT_WIDTH__ 16
#define __LDBL_MIN__ 2.2250738585072014e-308L
#define __DEC32_MAX__ 9.999999E96DF
#define __cpp_threadsafe_static_init 200806
#define __FLT32X_HAS_INFINITY__ 1
#define __INT32_MAX__ 0x7fffffff
#define __INT_WIDTH__ 32
#define __SIZEOF_LONG__ 4
#define __nios2 1
#define __STDC_ISO_10646__ 201706L
#define __UINT16_C(c) c
#define __PTRDIFF_WIDTH__ 32
#define __DECIMAL_DIG__ 17
#define __FLT64_EPSILON__ 2.2204460492503131e-16F64
#define __gnu_linux__ 1
#define __INTMAX_WIDTH__ 64
#define __FLT64_MIN_EXP__ (-1021)
#define __has_include_next(STR) __has_include_next__(STR)
#define __NIOS2 1
#define __LDBL_HAS_QUIET_NAN__ 1
#define __FLT64_MANT_DIG__ 53
#define __GNUC__ 8
#define __GXX_RTTI 1
#define __cpp_delegating_constructors 200604
#define __FLT_HAS_DENORM__ 1
#define __SIZEOF_LONG_DOUBLE__ 8
#define __BIGGEST_ALIGNMENT__ 4
#define __STDC_UTF_16__ 1
#define __FLT64_MAX_10_EXP__ 308
#define __NIOS2__ 1
#define __FLT32_HAS_INFINITY__ 1
#define __DBL_MAX__ double(1.7976931348623157e+308L)
#define __cpp_raw_strings 200710
#define __INT_FAST32_MAX__ 0x7fffffff
#define __DBL_HAS_INFINITY__ 1
#define __DEC32_MIN_EXP__ (-94)
#define __INTPTR_WIDTH__ 32
#define __FLT32X_HAS_DENORM__ 1
#define __INT_FAST16_TYPE__ int
#define __LDBL_HAS_DENORM__ 1
#define __cplusplus 201402L
#define __cpp_ref_qualifiers 200710
#define __DEC128_MAX__ 9.999999999999999999999999999999999E6144DL
#define __INT_LEAST32_MAX__ 0x7fffffff
#define __DEC32_MIN__ 1E-95DF
#define __DEPRECATED 1
#define __cpp_rvalue_references 200610
#define __DBL_MAX_EXP__ 1024
#define __WCHAR_WIDTH__ 32
#define __FLT32_MAX__ 3.4028234663852886e+38F32
#define __DEC128_EPSILON__ 1E-33DL
#define __PTRDIFF_MAX__ 0x7fffffff
#define __FLT32_HAS_QUIET_NAN__ 1
#define __GNUG__ 8
#define __LONG_LONG_MAX__ 0x7fffffffffffffffLL
#define __SIZEOF_SIZE_T__ 4
#define __cpp_rvalue_reference 200610
#define __cpp_nsdmi 200809
#define __SIZEOF_WINT_T__ 4
#define __LONG_LONG_WIDTH__ 64
#define __cpp_initializer_lists 200806
#define __FLT32_MAX_EXP__ 128
#define __cpp_hex_float 201603
#define __GCC_HAVE_DWARF2_CFI_ASM 1
#define __GXX_ABI_VERSION 1013
#define __FLT_MIN_EXP__ (-125)
#define __cpp_lambdas 200907
#define __INT_FAST64_TYPE__ long long int
#define __FLT64_DENORM_MIN__ 4.9406564584124654e-324F64
#define __DBL_MIN__ double(2.2250738585072014e-308L)
#define __FLT32X_EPSILON__ 2.2204460492503131e-16F32x
#define __FLT64_MIN_10_EXP__ (-307)
#define __DEC128_MIN__ 1E-6143DL
#define __REGISTER_PREFIX__ 
#define __UINT16_MAX__ 0xffff
#define __DBL_HAS_DENORM__ 1
#define __FLT32_MIN__ 1.1754943508222875e-38F32
#define __UINT8_TYPE__ unsigned char
#define __NO_INLINE__ 1
#define __FLT_MANT_DIG__ 24
#define __LDBL_DECIMAL_DIG__ 17
#define __VERSION__ "8.3.0"
#define __UINT64_C(c) c ## ULL
#define __cpp_unicode_characters 200704
#define _STDC_PREDEF_H 1
#define __cpp_decltype_auto 201304
#define __GCC_ATOMIC_INT_LOCK_FREE 1
#define __FLT32_MANT_DIG__ 24
#define __FLOAT_WORD_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __SCHAR_WIDTH__ 8
#define __INT32_C(c) c
#define __DEC64_EPSILON__ 1E-15DD
#define __ORDER_PDP_ENDIAN__ 3412
#define __DEC128_MIN_EXP__ (-6142)
#define __FLT32_MAX_10_EXP__ 38
#define __INT_FAST32_TYPE__ int
#define __UINT_LEAST16_TYPE__ short unsigned int
#define unix 1
#define __INT16_MAX__ 0x7fff
#define __cpp_rtti 199711
#define __SIZE_TYPE__ unsigned int
#define __UINT64_MAX__ 0xffffffffffffffffULL
#define __INT8_TYPE__ signed char
#define __cpp_digit_separators 201309
#define __ELF__ 1
#define __FLT_RADIX__ 2
#define __INT_LEAST16_TYPE__ short int
#define __LDBL_EPSILON__ 2.2204460492503131e-16L
#define __UINTMAX_C(c) c ## ULL
#define __SIG_ATOMIC_MAX__ 0x7fffffff
#define __GCC_ATOMIC_WCHAR_T_LOCK_FREE 1
#define __SIZEOF_PTRDIFF_T__ 4
#define __FLT32X_MANT_DIG__ 53
#define __FLT32X_MIN_EXP__ (-1021)
#define __DEC32_SUBNORMAL_MIN__ 0.000001E-95DF
#define __INT_FAST16_MAX__ 0x7fffffff
#define __FLT64_DIG__ 15
#define __UINT_FAST32_MAX__ 0xffffffffU
#define __UINT_LEAST64_TYPE__ long long unsigned int
#define __FLT_HAS_QUIET_NAN__ 1
#define __FLT_MAX_10_EXP__ 38
#define __LONG_MAX__ 0x7fffffffL
#define __DEC128_SUBNORMAL_MIN__ 0.000000000000000000000000000000001E-6143DL
#define __FLT_HAS_INFINITY__ 1
#define __cpp_unicode_literals 200710
#define __UINT_FAST16_TYPE__ unsigned int
#define __DEC64_MAX__ 9.999999999999999E384DD
#define __INT_FAST32_WIDTH__ 32
#define __CHAR16_TYPE__ short unsigned int
#define __PRAGMA_REDEFINE_EXTNAME 1
#define __SIZE_WIDTH__ 32
#define __INT_LEAST16_MAX__ 0x7fff
#define __DEC64_MANT_DIG__ 16
#define __INT64_MAX__ 0x7fffffffffffffffLL
#define __UINT_LEAST32_MAX__ 0xffffffffU
#define __FLT32_DENORM_MIN__ 1.4012984643248171e-45F32
#define __GCC_ATOMIC_LONG_LOCK_FREE 1
#define __SIG_ATOMIC_WIDTH__ 32
#define __INT_LEAST64_TYPE__ long long int
#define __INT16_TYPE__ short int
#define __INT_LEAST8_TYPE__ signed char
#define __DEC32_MAX_EXP__ 97
#define __INT_FAST8_MAX__ 0x7f
#define __INTPTR_MAX__ 0x7fffffff
#define __cpp_sized_deallocation 201309
#define linux 1
#define __cpp_range_based_for 200907
#define __FLT64_HAS_QUIET_NAN__ 1
#define __FLT32_MIN_10_EXP__ (-37)
#define __EXCEPTIONS 1
#define __nios2_little_endian 1
#define __LDBL_MANT_DIG__ 53
#define __DBL_HAS_QUIET_NAN__ 1
#define __FLT64_HAS_INFINITY__ 1
#define __SIG_ATOMIC_MIN__ (-__SIG_ATOMIC_MAX__ - 1)
#define __cpp_return_type_deduction 201304
#define __INTPTR_TYPE__ int
#define __UINT16_TYPE__ short unsigned int
#define __WCHAR_TYPE__ int
#define __SIZEOF_FLOAT__ 4
#define __UINTPTR_MAX__ 0xffffffffU
#define __INT_FAST64_WIDTH__ 64
#define __DEC64_MIN_EXP__ (-382)
#define __cpp_decltype 200707
#define __FLT32_DECIMAL_DIG__ 9
#define __INT_FAST64_MAX__ 0x7fffffffffffffffLL
#define __GCC_ATOMIC_TEST_AND_SET_TRUEVAL 1
#define __FLT_DIG__ 6
#define __UINT_FAST64_TYPE__ long long unsigned int
#define __INT_MAX__ 0x7fffffff
#define __INT64_TYPE__ long long int
#define __FLT_MAX_EXP__ 128
#define __DBL_MANT_DIG__ 53
#define __cpp_inheriting_constructors 201511
#define __INT_LEAST64_MAX__ 0x7fffffffffffffffLL
#define __DEC64_MIN__ 1E-383DD
#define __WINT_TYPE__ unsigned int
#define __UINT_LEAST32_TYPE__ unsigned int
#define __SIZEOF_SHORT__ 2
#define __LDBL_MIN_EXP__ (-1021)
#define __FLT64_MAX__ 1.7976931348623157e+308F64
#define __WINT_WIDTH__ 32
#define __INT_LEAST8_MAX__ 0x7f
#define __FLT32X_MAX_10_EXP__ 308
#define __LDBL_MAX_10_EXP__ 308
#define __ATOMIC_RELAXED 0
#define __DBL_EPSILON__ double(2.2204460492503131e-16L)
#define nios2 1
#define __UINT8_C(c) c
#define __FLT64_MAX_EXP__ 1024
#define __INT_LEAST32_TYPE__ int
#define __SIZEOF_WCHAR_T__ 4
#define NIOS2 1
#define __INT_FAST8_TYPE__ signed char
#define __GNUC_STDC_INLINE__ 1
#define __FLT64_HAS_DENORM__ 1
#define __FLT32_EPSILON__ 1.1920928955078125e-7F32
#define __DBL_DECIMAL_DIG__ 17
#define __STDC_UTF_32__ 1
#define __INT_FAST8_WIDTH__ 8
#define __DEC_EVAL_METHOD__ 2
#define __FLT32X_MAX__ 1.7976931348623157e+308F32x
#define __ORDER_BIG_ENDIAN__ 4321
#define __cpp_runtime_arrays 198712
#define __UINT64_TYPE__ long long unsigned int
#define __UINT32_C(c) c ## U
#define __INTMAX_MAX__ 0x7fffffffffffffffLL
#define __cpp_alias_templates 200704
#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
#define __FLT_DENORM_MIN__ 1.4012984643248171e-45F
#define __INT8_MAX__ 0x7f
#define __LONG_WIDTH__ 32
#define __UINT_FAST32_TYPE__ unsigned int
#define __CHAR32_TYPE__ unsigned int
#define __FLT_MAX__ 3.4028234663852886e+38F
#define __cpp_constexpr 201304
#define __INT32_TYPE__ int
#define __SIZEOF_DOUBLE__ 8
#define __cpp_exceptions 199711
#define __FLT_MIN_10_EXP__ (-37)
#define __FLT64_MIN__ 2.2250738585072014e-308F64
#define __INT_LEAST32_WIDTH__ 32
#define __INTMAX_TYPE__ long long int
#define __DEC128_MAX_EXP__ 6145
#define __FLT32X_HAS_QUIET_NAN__ 1
#define __ATOMIC_CONSUME 1
#define __GNUC_MINOR__ 3
#define __INT_FAST16_WIDTH__ 32
#define __UINTMAX_MAX__ 0xffffffffffffffffULL
#define __DEC32_MANT_DIG__ 7
#define __FLT32X_DENORM_MIN__ 4.9406564584124654e-324F32x
#define __DBL_MAX_10_EXP__ 308
#define __LDBL_DENORM_MIN__ 4.9406564584124654e-324L
#define __INT16_C(c) c
#define __cpp_generic_lambdas 201304
#define __STDC__ 1
#define __FLT32X_DIG__ 15
#define __PTRDIFF_TYPE__ int
#define __ATOMIC_SEQ_CST 5
#define __UINT32_TYPE__ unsigned int
#define __FLT32X_MIN_10_EXP__ (-307)
#define __UINTPTR_TYPE__ unsigned int
#define __DEC64_SUBNORMAL_MIN__ 0.000000000000001E-383DD
#define __DEC128_MANT_DIG__ 34
#define __LDBL_MIN_10_EXP__ (-307)
#define __SIZEOF_LONG_LONG__ 8
#define __cpp_user_defined_literals 200809
#define __GCC_ATOMIC_LLONG_LOCK_FREE 1
#define __FLT32X_MIN__ 2.2250738585072014e-308F32x
#define __LDBL_DIG__ 15
#define __FLT_DECIMAL_DIG__ 9
#define __UINT_FAST16_MAX__ 0xffffffffU
#define __GCC_ATOMIC_SHORT_LOCK_FREE 1
#define __INT_LEAST64_WIDTH__ 64
#define __UINT_FAST8_TYPE__ unsigned char
#define _GNU_SOURCE 1
#define __cpp_init_captures 201304
#define __ATOMIC_ACQ_REL 4
#define __ATOMIC_RELEASE 3

[ffontaine]

Here is an extract of the build log:

Building the Boost C++ Libraries.


    - has stat::st_mtim        : yes
    - has stat::st_mtimensec   : no
    - has stat::st_mtimespec   : no
    - native-atomic-int32-supported : no
    - native-syslog-supported  : yes
    - pthread-supports-robust-mutexes : yes
    - has_icu builds           : no
    - lockfree boost::atomic_flag : no
    - x86                      : no
    - arm                      : no
    - mips1                    : no
    - power                    : no
    - sparc                    : no
    - Boost.Config Feature Check: cxx11_defaulted_functions : yes
    - Boost.Config Feature Check: cxx11_noexcept : yes
    - Boost.Config Feature Check: cxx11_rvalue_references : yes
    - Boost.Config Feature Check: cxx11_static_assert : yes
    - std::fstream is moveable and swappable : yes
    - Has Large File Support   : yes

[Lastique]

According to the compiler output, the target does not support atomic operations (all *_LOCK_FREE macros equal to 1 instead of 2, which means runtime detection is required). Boost.Atomic requires compile-time knowledge about supported atomic operations, and has a hard requirement of the native atomic operations on bytes. Check if there is a compiler switch (-march) for your target that enables native atomic operations.

[ffontaine]

Thanks for your feedback, on most architectures, gcc provides "always lock-free" atomic types, but a few architectures (like nios2 or sparc v8) are limited to "sometimes lock-free" types. On buildroot, we manage this through the BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS variable:

# Atomic types can be:
#  - never lock-free
#  - sometimes lock-free
#  - always lock-free
# see https://en.cppreference.com/w/c/atomic/ATOMIC_LOCK_FREE_consts
#
# On most architectures, gcc provides "always lock-free" atomic types,
# but a few architectures are limited to "sometimes lock-free"
# types. This hidden option allows to know if the architecture
# provides "always lock-free" atomic types.
config BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS
	bool
	default y
	depends on !BR2_nios2
	depends on !BR2_ARM_CPU_ARMV4
	depends on !BR2_ARM_CPU_ARMV5
	depends on !BR2_sparc_v8
	depends on !BR2_m68k_cf5208

I'll disable atomic if BR2_TOOLCHAIN_SUPPORTS_ALWAYS_LOCKFREE_ATOMIC_INTS is false. Can you confirm that this hard requirement on native atomic operations on bytes has been added in boost 1.74.0 or should I backport this requirement on previous boost versions?

[Lastique]

Yes, the requirement appeared in 1.74.

[ffontaine]

Thanks for your help then this issue can be closed.