GLintptr

GLintptr is a data type defined by the OpenGL specification that represents a signed integer large enough to hold a pointer. It is used to express memory offsets within buffer objects and, when no buffer object is bound, to pass client-side pointers. The type provides a pointer-sized integer representation to accommodate different architectures and address spaces.

In practice, GLintptr is defined as a platform-dependent integral type, commonly corresponding to intptr_t. On 64-bit systems it is 64 bits, and on 32-bit systems it is 32 bits. It is paired with GLsizeiptr, a signed integer type that holds a size in bytes. This pairing allows OpenGL to specify both an offset and a length for data transfers and buffer operations in a way that matches pointer arithmetic across platforms.

Usage examples include functions such as glBufferSubData(target, GLintptr offset, GLsizeiptr size, const void data) and glMapBufferRange(target, GLintptr offset, GLsizeiptr length, GLbitfield access). In addition, when a buffer object is bound to an appropriate target (for example, an element array buffer), parameters that would otherwise be a client memory pointer are treated as byte offsets into the buffer. This applies to index data passed to functions like glDrawElements, where the indices can be supplied as an offset within the bound buffer.

GLintptr is one of the core GL type definitions used to ensure compatibility of pointer-sized values in the API, alongside GLsizeiptr and other size-related types.