Repository navigation
Analyzer: Adjust code for numeric IntPtr. #72348
Description
With the advert of the numeric IntPtr feature, nint is an alias for System.IntPtr just like int is an alias for System.Int32. We should add analyzers and fixers to make it clear to user code, especially to those who think that IntPtr represents an opaque pointer-sized value. Here's what the analyzers should do:
IDE0049should be updated to suggest convertingIntPtrtonintandUIntPtrtonuint.U?IntPtr.Zero➡0or(nu?int)0if it would introduce ambiguitynew U?IntPtr(x)➡xor(nu?int)xif it would introduce ambiguity, orunchecked((nu?int)x)if we are in acheckedcontext.x.ToU?Int32()➡checked((u?int)x)or(u?int)xif we are in acheckedcontextx.ToU?Int64()➡unchecked((u?long)x)or(u?long)xif we are in anuncheckedcontextx.ToPointer()➡(void*) x- Convert explicit casts between
U?IntPtrandu?intoru?long, tonu?int, while taking the overflow checking context into account (too many to list).
These analyzers and fixers should be triggered only if the underlying runtime supports numeric IntPtr. Some of them might be legal even without it but it's not necessary to make it more complicated.
Reacted by Buyaa Namnan
Reacted by NN
Activity
jeffhandley commentedon Jul 27, 2022
@tannergooding Do the details of this proposal match your expectations for the analyzer you had in mind?
tannergooding commentedon Jul 27, 2022
Yes, this looks to capture the most relevant details.
jkotas commentedon Jul 27, 2022
It would be nice for the code-fixer to suggest replacing
IntPtrwith actual pointer types where the code is actually operating on pointers.Blank replacing
IntPtrwithnintwill often make code harder to understand. See discussion in #70297dakersnar commentedon Aug 8, 2022
We're planning on getting an analyzer out that flags the known behavioral changes for 7.0, code fixers will be a future consideration (post 7.0).
jeffhandley commentedon Aug 12, 2022
I thought we had a separate issue tracking the analyzer itself, but we don't. Leaving a comment here to capture what the analyzer work is separate from the fixer as proposed in the description. From there, we can spawn off issue(s) as needed.
U?IntPtr.Zero➡0or(nu?int)0if it would introduce ambiguitynew U?IntPtr(x)➡xor(nu?int)xif it would introduce ambiguity, orunchecked((nu?int)x)if we are in acheckedcontext.x.ToU?Int32()➡checked((u?int)x)or(u?int)xif we are in acheckedcontextx.ToU?Int64()➡unchecked((u?long)x)or(u?long)xif we are in anuncheckedcontextx.ToPointer()➡(void*) xU?IntPtr, while taking the overflow checking context into accountIntPtroperator +(IntPtr, int): Unchecked: same behavior; Checked: may overflow now when it didn't before; Wrap in unchecked context to prevent the overflow and preserve behavioroperator -(IntPtr, int): Unchecked: same behavior; Checked: may overflow now when it didn't before; Wrap in unchecked context to prevent the overflow and preserve behaviorexplicit operator IntPtr(long): Checked: same behavior; Unchecked: will not throw an overflow exception when it could have before in 32-bit contexts; Wrap in a checked context to ensure the exception will be thrown as before in 32-bit contextsexplicit operator void*(IntPtr): Unchecked: same behavior; Checked: may overflow now when it didn't before; Wrap in unchecked context to prevent the overflow and preserve behaviorexplicit operator IntPtr(void*): Unchecked: same behavior; Checked: may overflow now when it didn't before; Wrap in unchecked context to prevent the overflow and preserve behaviorexplicit operator int(IntPtr): Checked: same behavior; Unchecked: will not throw an overflow exception when it could have before in 64-bit contexts; Wrap in checked context to ensure the exception will be thrown as before in 64-bit contextsUIntPtroperator +(UIntPtr, int): Unchecked: same behavior; Checked: may overflow now when it didn't before; Wrap in unchecked context to prevent the overflow and preserve behavioroperator -(UIntPtr, int): Unchecked: same behavior; Checked: may overflow now when it didn't before; Wrap in unchecked context to prevent the overflow and preserve behaviorexplicit operator UIntPtr(ulong): Checked: same behavior; Unchecked: will not throw an overflow exception when it could have before in 32-bit contexts; Wrap in a checked context to ensure the exception will be thrown as before in 32-bit contextsexplicit operator uint(UIntPtr): Checked: same behavior; Unchecked: will not throw an overflow exception when it could have before in 64-bit contexts; Wrap in checked context to ensure the exception will be thrown as before in 64-bit contextsbuyaa-n commentedon Mar 12, 2024
Looks only the 2nd check box is pending (Code simplification opportunities now available that could be suggested (but these are not changes in behavior to existing usage)) for which an issue was created #74518, so closing this issue