C compiler support

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C23 features

Note that this list may change, as the draft C23/2x standard evolves.

C23 core language features

This section is incomplete Reason: status for Apple Clang and other compilers supporting C2x

C23 feature	Paper(s)	GCC	Clang	MSVC	Apple Clang	EDG eccp	Intel C++	IBM XL C++	IBM Open XL C++ for AIX	IBM Open XL C++ for z/OS	Sun/Oracle C++	Embarcadero C++ Builder	Cray	Nvidia HPC C++ (ex PGI)*	Nvidia nvcc
_Static_assert with no message	N2265	9	9	Yes	Yes	6.5	2021.1.2 (clang based)
[[ nodiscard ]]	N2267	10	9		Yes	6.4	2021.1.2 (clang based)
[[ maybe_unused ]]	N2270	10	9		Yes	6.4	2021.1.2 (clang based)
[[ deprecated ]]	N2334	10	9		Yes	6.4	2021.1.2 (clang based)
Attributes	N2335 N2554	10	9		Yes	6.4	2021.1.2 (clang based)
IEEE 754 decimal floating-point types	N2341	4.2 (partial)* 12					13.0 (partial)*
[[ fallthrough ]]	N2408	10	9		Yes	6.4	2021.1.2 (clang based)
u8 character constants	N2418	10	15			6.5	2022.2
Removal of function definitions without prototype	N2432	10	15				2022.2
[[ nodiscard ]] with message	N2448	11	10		Yes	6.4	2021.1.2 (clang based)
Unnamed parameters in function definitions	N2480	11	11		Yes	6.4	2021.1.2 (clang based)
Labels before declarations and end of blocks	N2508	11	16	Partial*		6.5	17.0 *
Binary integer constants	N2549	4.3 * 11	2.9 * 9	19.0 (2015)* *	Yes	6.5	11.0 *
__has_c_attribute in preprocessor conditionals	N2553	11	9		Yes	6.5	2021.1.2 (clang based)
Allow duplicate attributes	N2557	11	13		Yes	6.5	2021.4 (clang-based
IEEE 754 interchange and extended types	N2601	7 (partial)* 14	6 (partial)*		Partial*
Digit separators	N2626	12	13	19.0 (2015)* *	Yes	6.5	18.0 *
#elifdef and #elifndef	N2645	12	13	19.40*	13.1.6*	6.5	2021.4
Type change of u8 string literals	N2653	13
[[ maybe_unused ]] for labels	N2662	11	16			6.5	2022.2
#warning	N2686	Yes	Yes		Yes	6.5	Yes
Bit-precise integer types ( _BitInt )	N2763	14 (partial)*	15			6.5	2022.2
[[ noreturn ]]	N2764	13	15			6.5	2022.2
Suffixes for bit-precise integer constants	N2775	14	15				2022.2
__has_include in preprocessor conditionals	N2799	5	Yes	19.11*	Yes	6.5	18.0
Identifier Syntax using Unicode Standard Annex 31	N2836	13	15			6.5	2022.2
Removal of function declarations without prototype	N2841	13	15				2022.2
Empty initializers	N2900	Partial* 13	Partial*		Partial*	Partial*	Partial*
typeof and typeof_unqual	N2927 N2930	Partial* 13	Partial* 16	19.39*	Partial*	Partial*	Partial*						Partial*
New spelling of keywords	N2934	13	16			6.5
Predefined true and false	N2935	13	15				2022.2
[[ unsequenced ]] and [[ reproducible ]]	N2956	15
Relax requirements for variadic parameter list	N2975	13	16			6.5	2023.1
Type inference in object definitions	N3007	13	18
#embed	N3017	15	19
constexpr objects	N3018	13	19
Improved Normal Enumerations	N3029	13	20 *
Enumerations with fixed underlying types	N3030	13	20 *
__VA_OPT__	N3033	8 13	12	19.39*		6.5
Storage-class specifiers for compound literals	N3038	13
nullptr	N3042	13	16
C23 feature	Paper(s)	GCC	Clang	MSVC	Apple Clang	EDG eccp	Intel C++	IBM XL C++	IBM Open XL C++ for AIX	IBM Open XL C++ for z/OS	Sun/Oracle C++	Embarcadero C++ Builder	Cray	Nvidia HPC C++ (ex PGI)*	Nvidia nvcc

C23 library features

This section is incomplete Reason: a different list for C standard libraries

C99 features

C99 core language features

This section is incomplete Reason: needs to list C compilers, verification

C99 feature	Paper(s)	GCC	Clang	MSVC	Apple Clang	EDG eccp	Intel C++	IBM XL C++	IBM Open XL C++ for AIX	IBM Open XL C++ for z/OS	Sun/Oracle C++	Embarcadero C++ Builder	Cray	Nvidia HPC C++ (ex PGI)*	Nvidia nvcc
Universal-character-names in identifiers	N/A	3.1	Yes	Yes
Increased translation limits	N590	0.9	N/A
// comments	N644	2.7	Yes	Yes
restrict pointers	N448	2.95	Yes	partial *
Enhanced arithmetic types	N815 N601 N620 N638 N657 N694 N809	Yes	partial	Maybe
Flexible array members	N/A	3.0	Yes	Yes
Variable-length array (VLA) types	N683	0.9	Yes
Variably-modified (VM) types	N2778	N/A	Yes
Designated initializers	N494	3.0	Yes	Yes
Non-constant initializers	N/A	1.21	N/A
Idempotent cvr-qualifiers	N505	3.0	N/A
Trailing comma in enumerator-list	N/A	0.9	Yes	Yes
Hexadecimal floating constants	N308	2.8	Yes	Yes
Compound literals	N716	3.1	Yes	Yes
Floating-point environment	N/A	partial	partial
Requiring truncation for divisions of signed integer types	N617	0.9	N/A
Implicit return 0 ; in the main() function	N/A	Yes	Yes	Yes
Declarations and statements in mixed order	N740	3.0	Yes	Yes
init-statement in for loops	N/A	Yes	Yes	Yes
inline functions	N741	4.3	Yes	Yes
Predefined variable __func__	N611	2.95	Yes	Yes
Cvr-qualifiers and static in [ ] within function declarations	N/A	3.1	Yes
Variadic macros	N707	2.95	Yes	Yes
_Pragma preprocessor operator	N634	3.0	Yes	partial *
Standard pragmas for floating-point evaluation	N631 N696	No	No								Yes
C99 feature	Paper(s)	GCC	Clang	MSVC	Apple Clang	EDG eccp	Intel C++	IBM XL C++	IBM Open XL C++ for AIX	IBM Open XL C++ for z/OS	Sun/Oracle C++	Embarcadero C++ Builder	Cray	Nvidia HPC C++ (ex PGI)*	Nvidia nvcc

See also

C++ documentation for compiler support