Re: [PATCH 1/3] scripts: common: fix pread_full() for windows

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hi,

On 11/28/25 4:00 PM, Maud Spierings wrote:
> On 11/28/25 15:56, Ahmad Fatoum wrote:
>> Hi,
>>
>> On 11/28/25 3:08 PM, Maud Spierings via B4 Relay wrote:
>>> From: Maud Spierings <maudspierings@gocontroll.com>
>>>
>>> pread() is not available for windows, convert to lseek() + read()
>>>
>>> Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
>>>
>>> ---
>>>
>>> I think this modifies the state of fd, I am not sure if pread() did this
>>> too. May be necessary to point the file pointer where it was before? On
>>> the other hand this reads the whole file so why.
>>
>> I would prefer to ship a pread implementation for windows instead that
>> takes care to lseek to wherever we need to read from and then lseek back
>> to the original offset as not to induce subtle breakage into other host
>> tools.
>>
> 
> just read the manpage a little better:
> pread() reads up to count bytes from file descriptor fd at offset
> offset (from the start of the file) into the buffer starting at
> buf.  The file offset is not changed.
> 
> So yeah it should indeed seek back, I'll get on that.

The new implementation should only be used when building for mingw.
Maybe just link it in the mingw makefile.

Cheers,
Ahmad

> 
>>
>>> ---
>>>   scripts/common.c | 6 +++++-
>>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/scripts/common.c b/scripts/common.c
>>> index a6eee968b7..544d295b7f 100644
>>> --- a/scripts/common.c
>>> +++ b/scripts/common.c
>>> @@ -202,8 +202,12 @@ int pread_full(int fd, void *buf, size_t size,
>>> loff_t offset)
>>>       size_t insize = size;
>>>       int now;
>>>   +    now = lseek(fd, offset, SEEK_SET);
>>> +    if (now < 0)
>>> +        return now;
>>> +
>>>       while (size) {
>>> -        now = pread(fd, buf, size, offset);
>>> +        now = read(fd, buf, size);
>>>           if (now == 0)
>>>               break;
>>>           if (now < 0)
>>>
>>
> 
> 

-- 
Pengutronix e.K.                  |                             |
Steuerwalder Str. 21              | http://www.pengutronix.de/  |
31137 Hildesheim, Germany         | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686  | Fax:   +49-5121-206917-5555 |