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Index > Compiler Internals > mov [eax], 1.0 (in 1.71.27+)

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dunkaist



Joined: 31 Jul 2015
Posts: 19
dunkaist
Hello,

starting with version 1.71.27 fasm complains on this line.
Code:
mov  [eax], 1.0
error: invalid value.    

Was this compatibility change intentional? Should such a code be modified as follows?
Code:
mov [eax], dword 1.0    

Now it looks very like to following code.
Code:
mov  [eax], 10
error: operand size not specified.    
[/code]
Post 05 Jun 2016, 00:55
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revolution
When all else fails, read the source


Joined: 24 Aug 2004
Posts: 16858
Location: In your JS exploiting you and your system
revolution
I think the existence of the error is correct but the error text is misleading. To guarantee you get what you want you should put the size override on the destination:
Code:
mov dword[eax],value    
If "value" is a float and you try to put it into a byte then you will get an error:
Code:
mov byte[eax],3.1415926 ;value cannot fit    
Post 05 Jun 2016, 05:14
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 7420
Location: Kraków, Poland
Tomasz Grysztar
Yes, the error message is incorrect here, it should be like in the "mov [eax],10" case. The size operator has to be required to distinguish "mov dword [eax],1.0" and "mov word [eax],1.0", the latter is allowed since the introduction of F16C instructions.
Post 05 Jun 2016, 07:43
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dunkaist



Joined: 31 Jul 2015
Posts: 19
dunkaist
Thank you for quick replies! I'll update existing code.
Post 05 Jun 2016, 16:18
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 7420
Location: Kraków, Poland
Tomasz Grysztar
I have corrected the handling of this error in 1.71.54.
Post 09 Jun 2016, 10:36
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