WriteCharToUser function (usermode_accessors.h)

The WriteCharToUser function safely writes a CHAR value to user-mode memory.

Syntax

void WriteCharToUser(
  volatile CHAR *Destination,
  CHAR          Value
);

Parameters

Destination

[out] A pointer to the user-mode memory location where the CHAR value will be written.

Value

[in] The CHAR value to write to the destination memory location.

Return value

None

Remarks

This function provides a safe way to write a CHAR value to user-mode memory. It ensures the provided address is a user-mode address before writing to it.

This function doesn't enforce alignment.

It raises a structured exception if the memory access fails, such as when the destination address isn't a user-mode address or is inaccessible.

This function will never be optimized away by the compiler, nor will the compiler create additional accesses to this memory location before the function is called or after the function returns (unless the source code explicitly performs these accesses). The memory access is performed with memory_order_relaxed semantics.

This function works on all versions of Windows, not just the latest. You need to consume the latest WDK to get the function declaration from the usermode_accessors.h header. You also need the library (umaccess.lib) from the latest WDK. However, the resulting driver will run fine on older versions of Windows.

Requirements

See also

ReadCharFromUser

WriteCharToUserMode