swprintf double precision format in ntdll

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AE

Joined: 07 Apr 2022
Posts: 70

AE 02 Feb 2023, 22:43

Code:

            proc Debug
                local  buf[512]:BYTE
                local  frm  du 'Value %1.9f',0
                local  val  dq 4.99999
                ;
                lea     rcx, [buf]
                lea     rdx, [frm]
                cinvoke swprintf,  rcx, rdx, [val]   ; ntdll  import!
                invoke  OutputDebugString, addr buf
                ret
            endp

Out: Value f

What is wrong with this case? Other types works fine.

And BTW what macros do you use to debug values mixed with the strings?

02 Feb 2023, 22:43

AsmGuru62

Joined: 28 Jan 2004
Posts: 1521
Location: Toronto, Canada

AsmGuru62 03 Feb 2023, 02:03

The function which will work is 'sprintf' from MSVCRT.DLL -- the native NTDLL does not support float point formatting.

Something like that:

Code:

; ---------------------------------------------------------------------------
section '.idata' import data readable writeable

    library kernel32,'KERNEL32.DLL',user32,'USER32.DLL',msvcrt,'MSVCRT.DLL'

    include 'API\Kernel32.Inc'
    include 'API\User32.Inc'

    import msvcrt,\
        log,'log',\
        pow,'pow',\
        atof,'atof',\
        sprintf,'sprintf'

03 Feb 2023, 02:03

AE

Joined: 07 Apr 2022
Posts: 70

AE 03 Feb 2023, 07:50

True, replacing 'ntdll' to 'msvcrt' in import helps.
Thx.

03 Feb 2023, 07:50

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