How to use multiple uncheckeds in c#

Question

Is there a way to use unchecked for a whole program or a whole block ?

I'm translating something from java that has the type long and lots of comparisons with constants that are unsigned long... Some places there a some switch's with 20~30 cases... Do I have to uncheck every case individualy or is there a faster/easier way to do it?

case 101: 
   return jjMoveStringLiteralDfa5_0(active0, 0x8002010000000000L, active1, 0x1L);

I have to change to:

   return jjMoveStringLiteralDfa5_0(active0, unchecked((long)0x8002010000000000L), active1, 0x1L);

but there are many cases... and it is in a parser generator with lots of IF's, so It would be better to have something to suppress those checks in the whole file instead of searching every possible place that would generate those unsigned long constants...

There is a way to set that on Visual Studio options but since I'm generating a parser I wanted to know if I could make that parser automaticaly not check for overflows/underflows, is that possible?

Yes, I wanted that it didn't check for those overflows when using ulong as long — nightshade, Jun 16 '14 at 22:01
While you're translating you might consider fixing the core problem... — H H, Jun 16 '14 at 22:03
@ErikPhilips it is working as long as i do that conversion... what I'm asking is if there is some command where I won't need to do that... like a global unchecked — nightshade, Jun 16 '14 at 22:07
It is a compiler switch, http://msdn.microsoft.com/en-us/library/h25wtyxf.aspx — Preston Guillot, Jun 16 '14 at 22:09
Why not change `jjMoveStringLiteralDfa5` to accept a `long` or perform the unchecked conversion or whatever? — Dour High Arch, Jun 16 '14 at 22:18
@PrestonGuillot However, the compiler switch is not enough to allow negative numbers to be expressed in hexadecimal two's complement. — Jeppe Stig Nielsen, Jun 16 '14 at 22:23
@DourHighArch The method `jjMoveStringLiteralDfa5` seems to require a `long` already; that is the problem. — Jeppe Stig Nielsen, Jun 16 '14 at 22:24
@DourHighArch I'm translating a lot of code (which I don't understand much of its logic) from java to c#... So the only thing I'm changing is the part that generate the files (my job is to generate the parser in c#, it is currently being generated in java)... I could try to change some types that are long to ulong but if those types happen to be needed somewhere else then I'll completely destroy other part of my program... java seems to have an IMPLICIT cast from ULONG to LONG but C# doesn't if the value is using the MSB... =\ — nightshade, Jun 16 '14 at 22:30
@JeppeStigNielsen You're right, I didn't even bother to look at what was actually happening in the code snippets here. — Preston Guillot, Jun 16 '14 at 22:34

Jeppe Stig Nielsen · Accepted Answer · 2014-06-16T22:54:24.673

3

If you want to use hexadecimal literals to express negative integers via the two's complement convention, you simply have to provide both a cast and an explicit use of the unchecked keyword. Example:

sbyte b = unchecked((sbyte)0xAB);
short s = unchecked((short)0xABCD);
int i = unchecked((int)0xABCDABCD);
long l = unchecked((long)0xABCDABCDABCDABCD);

It is not enough that the default context (as defined by C# compiler switch and/or csproj file) is the "unchecked" context.

If you can use the unsigned types (for example uint), you won't have this problem. But the unsigned types are typically not used by the BCL, and are not considered "CLS compliant".

Just make it entirely clear, with positive literals you need neither cast nor unchecked keyword:

sbyte b = 0x2E;
short s = 0x2E3F;
int i = 0x2E3F2E3F;
long l = 0x2E3F2E3F2E3F2E3F;

For constant expressions implicit conversions exist to make this easy, see Implicit constant expression conversions.

edited Jun 16 '14 at 22:54

answered Jun 16 '14 at 22:15

Jeppe Stig Nielsen

60,409
11
110
181

but is there a way for me to make that cast implicit so I won't have to be casting all the time? like: "whenever you need to convert ulong to long, do like this (my_conversion)" – nightshade Jun 16 '14 at 22:21
@nightshade You would have to call your own method, which could be an extension method. EDIT: The conversion would no longer be done at compile-time; it would be a run-time thing (but possibly "empty" performance hit). – Jeppe Stig Nielsen Jun 16 '14 at 22:26
Hum... guess I'll just hit CTRL + F and find all the "0x" string in the part generating the code and add (long) or (int) before it then... – nightshade Jun 16 '14 at 22:38

How to use multiple uncheckeds in c#

1 Answers1

Linked