How can I safely convert a void* pointer to an integer in C ?

Converting a Pointer into an Integer

In a situation where a void* argument needs to be converted into a suitable type, it's crucial to ensure compatibility across different machine architectures.

On a 64-bit machine, casting a void* to an int may result in precision loss. To address this, a modern C approach involves using reinterpret_cast. This ensures a portable and efficient conversion.

Correct Integer Type:

To store a pointer as an integer correctly, the appropriate type is uintptr_t or intptr_t, defined in for C99 or the std namespace for C 11.

• C 11 (and onwards): std::uintptr_t
• C 03: uintptr_t (wrapped in extern "C" { if necessary})
• C99: uintptr_t

Correct Casting Operator:

In C , reinterpret_cast is the preferred cast for pointer conversions. Avoid using the C cast.

Example:

#include <cstdint>

void *p;
std::uintptr_t i = reinterpret_cast<std::uintptr_t>(p);

Related Questions:

• What is the uintptr_t data type?

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