Spec out numeric IntPtr by jcouv · Pull Request #6031 · dotnet/csharplang

jcouv · 2022-04-19T05:12:27Z

Rekkonnect · 2022-04-19T11:31:59Z

proposals/numeric-intptr.md

+For the predefined operators, the number of bits to shift is computed as follows:
+
+- When the type of `x` is `int`, **`nint`** or `uint`, the shift count is given by the low-order five bits of `count`. In other words, the shift count is computed from `count & 0x1F`.
+- When the type of `x` is `long`, **`nuint`** or `ulong`, the shift count is given by the low-order six bits of `count`. In other words, the shift count is computed from `count & 0x3F`.


I think nuint belongs to the above category here #Resolved

Shouldn't nuint be masked to (sizeof(nuint) * 8) - 1 (0x3F on 64-bit and 0x1F on 32-bit)? If it's exclusively masked to 0x3F it will become non-deterministic for what the computed result is when over shifting is involved on a 32-bit platform.

tannergooding · 2022-04-19T19:21:38Z

proposals/numeric-intptr.md

+  nint operator <<(nint x, nint count);
+  nuint operator <<(nuint x, nint count);


Shouldn't count be int for consistency with the other shift operators?

Or is this including the relaxations from #4666 ? #Resolved

Good catch. Bad search&replace ;-)

proposals/numeric-intptr.md

333fred · 2022-05-24T22:15:03Z

proposals/numeric-intptr.md

+- `IntPtr - int`
+- `IntPtr -> int`
+- `long -> IntPtr`
+- `void* -> IntPtr`


I don't think this could overflow? Aren't these always the same size? #Resolved

C# considered pointers as unsigned, so this can technically overflow.

Yup. Chuck caught that. It's covered in the breaking changes document and in OverflowPointerConversion test.

333fred · 2022-05-24T22:15:51Z

proposals/numeric-intptr.md

+
+### Breaking changes
+
+One of the main impacts of this design is that `System.IntPtr` and `System.IntPtr` gain some built-in operators (conversions, unary and binary).  


Was one of these supposed to be UIntPtr? #Resolved

Indeed. Thanks

cston · 2022-05-24T23:59:50Z

proposals/numeric-intptr.md

+
+## 8.8 Unmanaged types
+
+In other words, an __unmanaged_type__ is one of the following:


unmanaged_type

Consider using italics rather than bold to match the existing spec and to avoid indicating a change. #Resolved

cston · 2022-05-25T00:05:08Z

proposals/numeric-intptr.md

+
+# 11 Expressions
+
+#### 11.6.4.6 Better conversion target


11.6.4.6 Better conversion target

Is there any change in this section? #Resolved

There would be a change inside the ellipsis ("Specifically: ..."), but I didn't spell it out. I think the general rule is clear enough.

cston · 2022-05-25T00:07:01Z

proposals/numeric-intptr.md

+
+\[...] The number of expressions in the *argument_list* shall be the same as the rank of the *array_type*, and each expression shall be of type `int`, `uint`, **`nint`, `nuint`**, `long`, or `ulong,` or shall be implicitly convertible to one or more of these types.
+
+#### 11.7.10.2 Array access


11.7.10.2 Array access

Should this section include additions for nint and nuint? #Resolved

cston · 2022-05-25T00:16:00Z

proposals/numeric-intptr.md

+
+For the predefined operators, the number of bits to shift is computed as follows:
+\[...]
+- When the type of `x` is `nint` or `nuint`, the shift count is given by the low-order five bits of `count` on a 32 bits platform, or the lower-order six bits of `count` on a 64 bits platform.  


32 bits

Should these be "32 bit" and "64 bit" rather than "... bits" here and in the next sentence? #Closed

cston · 2022-05-25T00:23:12Z

proposals/numeric-intptr.md

+### Breaking changes
+
+One of the main impacts of this design is that `System.IntPtr` and `System.UIntPtr` gain some built-in operators (conversions, unary and binary).  
+Those include `checked` operators, which means that some operators on those types will now throw when overflowing. For example:


that some operators on those types

Perhaps "the following operators" to indicate this is the complete list of overflow changes. #Closed

I don't think that's the complete list. How about multiplication?

Multiplication is not defined for IntPtr with C#10.

Good point. Thanks
Fixed

cston · 2022-05-25T16:38:02Z

proposals/numeric-intptr.md

+For the predefined operators, the number of bits to shift is computed as follows:
+\[...]
+- When the type of `x` is `nint` or `nuint`, the shift count is given by the low-order five bits of `count` on a 32 bits platform, or the lower-order six bits of `count` on a 64 bits platform.  
+The shift count is computed from `count & (sizeof(nint) * 8 - 1)`, which is `count & 0x1F` on a 32 bits platform and `count & 0x3F` on a 64 bits platform.


count & (sizeof(nint) * 8 - 1), which is

The calculation using sizeof(nint) seems like an implementation detail. Consider omitting that part from the spec. #Closed

cston · 2022-05-25T18:43:20Z

proposals/numeric-intptr.md

+
+## 8.8 Unmanaged types
+
+In other words, an **unmanaged_type** is one of the following:


unmanaged_type

Should this be a single * or _ for italics? #Resolved

Spec out numeric IntPtr

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jcouv self-assigned this Apr 19, 2022

jcouv mentioned this pull request Apr 19, 2022

Test plan for "numeric IntPtr" dotnet/roslyn#60578

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Vectorized MemoryExtensions.CommonPrefixLength dotnet/runtime#68210

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Champion: numeric IntPtr #6065

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jcouv merged commit 710d778 into dotnet:main May 25, 2022

jcouv deleted the numeric-intptr branch May 25, 2022 19:01

		nint operator <<(nint x, nint count);
		nuint operator <<(nuint x, nint count);


		### Breaking changes

		One of the main impacts of this design is that `System.IntPtr` and `System.IntPtr` gain some built-in operators (conversions, unary and binary).


		## 8.8 Unmanaged types

		In other words, an __unmanaged_type__ is one of the following:


		\[...] The number of expressions in the argument_list shall be the same as the rank of the array_type, and each expression shall be of type `int`, `uint`, `nint`, `nuint`, `long`, or `ulong,` or shall be implicitly convertible to one or more of these types.

		#### 11.7.10.2 Array access


		## 8.8 Unmanaged types

		In other words, an unmanaged_type is one of the following:

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jcouv commented Apr 19, 2022 •

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