DbgPrint function (wdm.h)

The DbgPrint routine sends a message to the kernel debugger when the conditions that you specify apply (see the Remarks section below).


ULONG DbgPrint(
  PCSTR Format,



Specifies a pointer to the format string to print. The Format string supports most of the printf-style format specification fields. However, the Unicode format codes (%C, %S, %lc, %ls, %wc, %ws, and %wZ) can only be used with IRQL = PASSIVE_LEVEL. The DbgPrint routine does not support any of the floating point types (%f, %e, %E, %g, %G, %a, or %A).


Specifies arguments for the format string, as in printf.

Return value

If successful, DbgPrint returns the NTSTATUS code STATUS_SUCCESS; otherwise it returns the appropriate error code.


DbgPrint and DbgPrintEx can be called at IRQL<=DIRQL. However, Unicode format codes (%C, %S, %lc, %ls, %wc, %ws, and %wZ) can be used only at IRQL=PASSIVE_LEVEL. Also, because the debugger uses interprocess interrupts (IPIs) to communicate with other processors, calling DbgPrint at IRQL>DIRQL can cause deadlocks.

Only kernel-mode drivers can call the DbgPrint routine.

DbgPrint sends a message only if certain conditions apply. Specifically, it behaves like the DbgPrintEx routine with the DEFAULT component and a message importance level of DPFLTR_INFO_LEVEL. In other words, the following two function calls are identical:

DbgPrint ( Format, arguments )

DbgPrintEx ( DPFLTR_DEFAULT_ID, DPFLTR_INFO_LEVEL, Format, arguments )

For more information about message filtering, components, and message importance level, see Reading and Filtering Debugging Messages.

It is recommended that you use DbgPrintEx instead of DbgPrint, since this allows you to control the conditions under which the message is sent.

Unless it is absolutely necessary, you should not obtain a string from user input or another process and pass it to DbgPrint. If you do use a string that you did not create, you must verify that this is a valid format string, and that the format codes match the argument list in type and quantity. The best coding practice is for all Format strings to be static and defined at compile time.

There is no upper limit to the size of the Format string or the number of arguments. However, any single call to DbgPrint will only transmit 512 bytes of information. There is also a limit to the size of the DbgPrint buffer. See DbgPrint Buffer and the Debugger for details.


Requirement Value
Target Platform Universal
Header wdm.h (include Wdm.h)
Library NtDll.lib (user mode); NtosKrnl.lib (kernel mode)
DLL NtDll.dll (user mode); NtosKrnl.exe (kernel mode)
IRQL IRQL <= DIRQL (see Comments section)

See also