mov [eax], 1.0 (in 1.71.27+)

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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: 24

dunkaist 05 Jun 2016, 00:55

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]

05 Jun 2016, 00:55

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20759
Location: In your JS exploiting you and your system

revolution 05 Jun 2016, 05:14

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

05 Jun 2016, 05:14

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8466
Location: Kraków, Poland

Tomasz Grysztar 05 Jun 2016, 07:43

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.

05 Jun 2016, 07:43

dunkaist

Joined: 31 Jul 2015
Posts: 24

dunkaist 05 Jun 2016, 16:18

Thank you for quick replies! I'll update existing code.

05 Jun 2016, 16:18

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8466
Location: Kraków, Poland

Tomasz Grysztar 09 Jun 2016, 10:36

I have corrected the handling of this error in 1.71.54.

09 Jun 2016, 10:36

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