"Canonical" way of changing the size of off_t, ino_t, ...

[Stefan Heinzmann]

On 27/04/2025 20:47, Brian Inglis wrote:
> On 2025-04-27 10:27, Stefan Heinzmann wrote:
>> Hello list,
>>
>> I am using the newlib build for arm-none-eabi from ArchLinux for 
>> simplicity, but I now need to change the size of some predefined POSIX 
>> types. I wasn't able to find clear instructions how to do this 
>> properly, hence my question here.
>>
>> The default sizes of offs_t, ino_t, and possibly other types are too 
>> small for my use. Ideally I would like to customize the newlib build 
>> in a way that doesn't require the user builds to define anything, i.e. 
>> that the correct sizes are picked up from the newlib headers 
>> automatically. How do I do that? Are there configuration options I can 
>> use when building newlib? Do I have to patch the source, and if so, 
>> where?
>>
>> I note that there is support for off64_t and the respective functions, 
>> but I would prefer to have off_t defined as 64-bit, in a way similar 
>> to _FILE_OFFSET_BITS=64 in glibc.
>>
>> Similarly, how do I make ino_t larger? What about dev_t, and other 
>> POSIX types?
>>
>> Thanks for your help!
> 
> Please first read the FAQ, and follow all the steps, but ensure that you 
> do not redefine anything provided or assumed by your compiler or binutils:
> 
>      https://www.sourceware.org/newlib/faq.html
> 

I read the FAQ again, but it didn't get me any further. I don't want to 
port to a new platform, I just want to change the definition of a couple 
of types. Since I'm dealing with arm-none-eabi, there's no underlying 
system whose definitions I'd have to follow.

The types I want to modify are POSIX types, so I don't see how the 
compiler or binutils would have a bearing on it.

I note that include/sys/_types.h contains code like this:

#ifndef __machine_ino_t_defined
     // define __ino_t in some system dependent way
#endif

which suggests to me that there is a method to provide such definitions 
from the outside. I don't quite understand how this is meant to be used, 
and whether it is a hook that I can employ to insert my definition 
without needing to patch the source.

Or am I looking at the wrong place altogether?

Thanks
Stefan