Fix printing of unsigned integers #1896

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1. Smit-create commented on Jun 13, 2023

   

   Smit-create

   on Jun 13, 2023

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   So it needs a fix in the LLVM backend, and the fix basically requires keeping the value between [0, 2**(kind*8)). This should be handled at every assignment of unsigned integers and also while initializing. We need not worry about C backend as it will handle the same by itself.

   This also needs some more fixes in LLVM because right now we treat i8 the same as u8 while i8 is unable to store 255. So we need to fix this by:

   u_type = getIntType(max(a_kind*2, 8));
   
2. certik commented on Jun 13, 2023

   

   certik

   on Jun 13, 2023

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   LLVM treats u8 and i8 the same. It's the same LLVM type. The u8(255) is exactly the same bit representation as i8(-1). So I think the only fix we have to do is in the visit_Print() to treat the u8 correctly.
3. certik

   added a commit that references this issue on Jun 13, 2023

   Print unsigned ints correctly

   ...

   This issue will close once commit 4d2c137 is merged into the 'main' branch.

   4d2c137
4. Smit-create commented on Jun 13, 2023

   

   Smit-create

   on Jun 13, 2023

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   The fix I was suggesting not just only applies to print. If we fix just print there can be many other failures for the same reason. See the following:

   def main():
       siz: Const[u8] = u8(128)
       ai16: i16[siz] = empty(siz, dtype=int16)
   
   main()
   

   This fails in LLVM but not in C because in LLVM siz is -1.
5. certik

   closed this as completedin #1897on Jun 13, 2023
6. certik commented on Jun 13, 2023

   

   certik

   on Jun 13, 2023

   Last edited by certik

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   The example you posted doesn't work: #1898. But assuming it "works", for now I would not allow unsigned integers in empty. So empty(siz) should give an error message in AST->ASR as well as in verify() that unsigned integer is not supported. In ASR this ends up being part of the "dimensions" and we should enforce in verify() that only signed integers are allowed. I made this #1899.