ckd_add

Defined in header `<stdckdint.h>`
template< class type1, class type2, class type3 > bool ckd_add( type1* result, type2 a, type3 b );		(since C++26)

Computes the addition x + y and stores the result into *result. The addition is performed as if both operands were represented in a signed integer type with infinite range, and the result was then converted from this integer type to type1. If the value assigned to *result correctly represents the mathematical result of the operation, it returns false. Otherwise, it returns true. In this case, the value assigned to *result is the mathematical result of the operation wrapped around to the width of *result.

Parameters

a, b	-	integer values
result	-	address of where result should be stored

Return value

false if the value assigned to *result correctly represents the mathematical result of the addition, true otherwise.

Note

The function template ckd_add has the same semantics as the corresponding type-generic macro with the same name specified in C23.

Each of the types type1, type2, and type3 is a cv-unqualified signed or unsigned integer type.

It is recommended to produce a diagnostic message if type2 or type3 are not suitable integer types, or if *result is not a modifiable lvalue of a suitable integer type.

Feature-test macro	Value	Std	Feature
`__cpp_lib_stdckdint_h`	`202603L`	(C++26)	Compatibility header `<stdckdint.h>` for C checked integer operations

Example

#include <cstdint>
#include <limits>
#include <print>
#include <stdckdint.h>

int main()
{
    const std::uint8_t x{14};
    std::uint16_t y{28}, result1{};
    bool overflow{};

    overflow = ckd_add(&result1, x, y);
    std::println("{} + {} => {} ({})", x, y, result1, overflow ? "Overflow" : "OK");

    y = std::numeric_limits<std::uint16_t>::max();
    overflow = ckd_add(&result1, x, y);
    std::println("{} + {} => {} ({})", x, y, result1, overflow ? "Overflow" : "OK");

    std::uint32_t result2{};
    overflow = ckd_add(&result2, x, y);
    std::println("{} + {} => {} ({})", x, y, result2, overflow ? "Overflow" : "OK");
}

Output:

14 + 28 => 42 (OK)
14 + 65535 => 13 (Overflow)
14 + 65535 => 65549 (OK)

References

C++26 standard (ISO/IEC 14882:2026):

29.11.2 Checked integer operations