EngRestoreFloatingPointState function (winddi.h)

The EngRestoreFloatingPointState function restores the Windows 2000 (and later) kernel floating-point state after the driver uses any floating-point or MMX hardware instructions.

Syntax

BOOL EngRestoreFloatingPointState(
  [in] VOID *pBuffer
);

Parameters

[in] pBuffer

Pointer to the buffer whose contents were filled by EngSaveFloatingPointState.

Return value

EngRestoreFloatingPointState returns TRUE if successful. Otherwise, it returns FALSE.

Remarks

The driver must save the current kernel floating-point state before using floating-point hardware instructions. On Intel architecture systems, this permits the use of MMX instructions if they are supported by the processor. Drivers that do not properly use EngSaveFloatingPointState and EngRestoreFloatingPointState when using floating-point or MMX hardware will cause random floating-point or MMX corruption in the calling application.

On every call to the driver, the driver must call EngSaveFloatingPointState once to preserve kernel state before using floating-point or MMX operations. It must also call EngRestoreFloatingPointState once after all floating-point or MMX operations are complete to reset the kernel state.

GDI automatically saves the floating-point state for any calls to a driver's DrvEscape routine when the escape is OPENGL_CMD, OPENGL_GETINFO, or MCDFUNCS.

Requirements

See also

DrvEscape

EngSaveFloatingPointState