问题
Two questions:
1.
In "ntdef.h" the NTSTATUS is defined as follow:
typedef __success(return >= 0) LONG NTSTATUS;
what the hell is the "__success(return >= 0)"?
2.
In "ntstatus.h", STATUS_SUCCESS is defined to 0.
#define STATUS_SUCCESS ((NTSTATUS)0x00000000L) // ntsubauth
But the NT_SUCCESS macro in "ntdef.h" is:
#define NT_SUCCESS(Status) (((NTSTATUS)(Status)) >= 0)
Shouldn't it be "Status == 0" ?
回答1:
__success is an "Advanced Annotation" defined in SpecStrings_strict.h, which defines it as follows.
* __success(expr) T f() : indicates whether function f succeeded or * not. If is true at exit, all the function's guarantees (as given * by other annotations) must hold. If is false at exit, the caller * should not expect any of the function's guarantees to hold. If not used, * the function must always satisfy its guarantees. Added automatically to * functions that indicate success in standard ways, such as by returning an * HRESULT.
The reason that NT_SUCCESS
doesn't do a strict test against STATUS_SUCCESS (0)
is probably that other codes like STATUS_PENDING
aren't actually failures.
回答2:
The fragment __success(return >= 0)
is a SAL annotation, which gives a clue to the PreFast tool about what the intended semantics of the macro are. This is used to do static analysis and identify potential bugs.
The NT_SUCCESS
macro tests for >= 0
because there are success codes other than STATUS_SUCCESS
. Some success codes include extra information about the outcome of the operation, although at the moment I can only think of S_FALSE
, which notifies the caller that the operation succeeded, but the result was false. As a rule, success codes are equal to or greater than zero, and failure codes are less than zero.
[Strictly speaking, S_FALSE
is an HRESULT
, not an NT_STATUS
, though the two types have the same size and similar conventions.]
回答3:
__success is described nicely dead-link.
Answer to 2 is No, all positive codes are non-failures. They may mean something other than OK though.
来源:https://stackoverflow.com/questions/3378622/how-to-understand-the-ntstatus-nt-success-typedef-in-windows-ddk