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Re: integer overflow in muli instruction
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From: |
Bruno Haible |
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Subject: |
Re: integer overflow in muli instruction |
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Date: |
Tue, 23 Feb 2021 20:21:38 +0100 |
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User-agent: |
KMail/5.1.3 (Linux/4.4.0-201-generic; KDE/5.18.0; x86_64; ; ) |
Jose E. Marchesi wrote:
> So I think at this point we are good when it comes to detecting overflow
> in signed operations.
There is a problem, though: A literal that was printed cannot be parsed
when viewed as an expression:
(poke) .set obase 10
(poke) -2*0x4000000000000000
-9223372036854775808L
(poke) -9223372036854775808L
<stdin>:1:1: error: expression overflows
-9223372036854775808L;
^
What's odd is that this works in base 16:
(poke) .set obase 16
(poke) -2*0x4000000000000000
0x8000000000000000L
(poke) 0x8000000000000000L
0x8000000000000000L
Apparently because in base 16, signed integers are printed as if they were
unsigned. (Not sure whether this is intentional?)
Bruno