Standard library header <ciso646> (until C++20), <iso646.h>
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<forward_list> (C++11)
<hive> (C++26)
<mdspan> (C++23)
<span> (C++20)
<unordered_map> (C++11)
<unordered_set> (C++11)
<generator> (C++23)
<ranges> (C++20)
<cuchar> (C++11)
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<codecvt> (C++11/17/26*)
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<cfenv> (C++11)
<linalg> (C++26)
<numbers> (C++20)
<random> (C++11)
<simd> (C++26)
<stdckdint.h> (C++26)
<chrono> (C++11)
<ccomplex> (C++11/17/20*)
<ciso646> (until C++20)
<cstdalign> (C++11/17/20*)
<cstdbool> (C++11/17/20*)
<ctgmath> (C++11/17/20*)
<cinttypes> (C++11)
<filesystem> (C++17)
<print> (C++23)
<spanstream> (C++23)
<strstream> (C++98/26*)
<syncstream> (C++20)
<atomic> (C++11)
<barrier> (C++20)
<condition_variable> (C++11)
<future> (C++11)
<hazard_pointer> (C++26)
<latch> (C++20)
<mutex> (C++11)
<rcu> (C++26)
<semaphore> (C++20)
<shared_mutex> (C++14)
<stdatomic.h> (C++23)
<stop_token> (C++20)
<thread> (C++11)
<execution> (C++17)
This header was originally in the C standard library as <iso646.h>.
Compatibility header, in C defines alternative operator representations which are keywords in C++.
This means that in a conforming implementation, including this header has no effect.
[edit] Notes
In old or nonconforming compilers, using the alternative operator representations may still require including this header.
<ciso646> is removed in C++20. Corresponding <iso646.h> is still available in C++20.
Prior to C++20, including <ciso646> was sometimes used as a technique for obtaining definitions of implementation-specific library version macros without causing other effects.
As of C++20, the header <version> was added for this purpose.
Run this code
#include <ciso646> #ifdef _LIBCPP_VERSION #error Using LLVM libc++ #elif __GLIBCXX__ // Note: only version 6.1 or newer define this in ciso646 #error Using GNU libstdc++ #elif _CPPLIB_VER // Note: used by Visual Studio #error Using Microsoft STL #else #error Using an unknown standard library #endif
Possible output:
main.cpp:7:2: error: Using Microsoft STL #error Using Microsoft STL ^ 1 error generated.