Using cinvoke printf

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vua72

Joined: 22 Jan 2011
Posts: 2

vua72 26 Mar 2011, 15:10

I'm trying to use calling of cinvoke for console i/o.
With integers it works fine.
But with floating point it correct works only with dq, not dd format.
What is wrong?

Code:

 format pe; console
 entry start
 include 'win32ax.inc'
 section '.code' code readable executable

start:
   cinvoke scanf, fl, varq
   cinvoke printf, fl, dword[varq], dword[varq+4]
   cinvoke printf, cr
   cinvoke scanf, f4, vard
   cinvoke printf, f4, dword[vard] ; not work
exit:
   invoke ExitProcess, 0;

section '.data' data readable writeable
 cr db 13,10,0
 f4 db '%f', 0
 fl db '%lf', 0
 varq dq ?
 vard dd ?
section '.idata' import data readable writeable
library msvcrt, 'msvcrt.dll', kernel32, 'kernel32.dll'
import msvcrt, printf, 'printf', getchar,'getchar', scanf,'scanf'
import kernel32, ExitProcess,'ExitProcess'

26 Mar 2011, 15:10

klavs.pr

Joined: 20 Apr 2010
Posts: 20
Location: Latvia

klavs.pr 26 Mar 2011, 15:54

Not sure, but isn't floating point numbers always at least 64bit long?

26 Mar 2011, 15:54

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20451
Location: In your JS exploiting you and your system

revolution 26 Mar 2011, 23:25

'%f' and '%lf' both expect a qword floating point number. Change your line to this and you will see the result.

Code:

   cinvoke printf, f4, dword[varq], dword[varq+4]

26 Mar 2011, 23:25

madmatt

Joined: 07 Oct 2003
Posts: 1045
Location: Michigan, USA

madmatt 27 Mar 2011, 13:55

the printf function only accepts 64bit floats so you'll have to store it as a double:

Code:

fld [vard]
fstp [vartempq]

27 Mar 2011, 13:55

vua72

Joined: 22 Jan 2011
Posts: 2

vua72 09 Apr 2011, 18:09

madmatt wrote:

the printf function only accepts 64bit floats so you'll have to store it as a double:
Code:
fld [vard]
fstp [vartempq]    

Thanks, where I can read about this?

09 Apr 2011, 18:09

madmatt

Joined: 07 Oct 2003
Posts: 1045
Location: Michigan, USA

madmatt 09 Apr 2011, 21:18

vua72 wrote:

madmatt wrote:
the printf function only accepts 64bit floats so you'll have to store it as a double:
Code:
fld [vard]
fstp [vartempq]    
Thanks, where I can read about this?

To read more about printf (also scroll down to 'format specifications'):
http://msdn.microsoft.com/en-us/library/wc7014hz.aspx

A little better printf example:

Code:

proc MAIN
     local  mydouble:QWORD, myfloat:DWORD

     mov     [myfloat], 3.141
     fld     [myfloat]
     fstp    [mydouble]
     cinvoke printf, "fp number %f", double [mydouble]
endp

_________________
Gimme a sledge hammer! I'LL FIX IT!

09 Apr 2011, 21:18

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