Allow user to override LWIP_PROVIDE_ERRNO

[Zob314]

This doesn't allow LWIP_PROVIDE_ERRNO to be overridden:
https://github.com/STMicroelectronics/stm32_mw_lwip/blob/f0d19c3a6e7420248775b5163b8dbf1fc2371331/system/arch/cc.h#L40-L42
Suggest replacing with the following:

#if !defined(LWIP_ERRNO_STDINCLUDE) && !defined(LWIP_ERRNO_INCLUDE) && !defined(LWIP_PROVIDE_ERRNO)
#define LWIP_PROVIDE_ERRNO
#endif

to align with this comment:
https://github.com/STMicroelectronics/stm32_mw_lwip/blob/f0d19c3a6e7420248775b5163b8dbf1fc2371331/src/include/lwip/opt.h#L47-L52

[thornley-permaconn]

I had a similar issue, although at least in my case I was able to override in lwipopts.h, with this: -

/* USER CODE BEGIN 1 /
#undef LWIP_PROVIDE_ERRNO
#define LWIP_ERRNO_STDINCLUDE
/ USER CODE END 1 */

It is obtuse and would be better implemented as suggested.

In my case, this comes about if you enable configUSE_NEWLIB_REENTRANT (also missing from CubeMX) for FreeRTOS (which is AFAIK required for proper threadsafe newlib usage).

[ASELSTM]

ST Internal Reference: 126118

[khevessy]

Isn't this the same problem as this? However that pull request just removes the errno declaration from Middlewares/Third_Party/LwIP/system/OS/sys_arch.c which does not seem to be correct.

[ALABSTM]

Fixed in release 2.1.3 of 08/13/2023.

[pedro-fuoco]

Hi @ALABSTM, I am interested in undefining LWIP_PROVIDE_ERRNO in order to use the errno definition provided by newlib. I have looked at the 2.1.3 release commits and the issue doesn't seem to be solved, I still get a redefinition error unless I use @Zob314's original suggestion.

It seems like the core of this issue, which is allowing the user to control whether LWIP_PROVIDE_ERRNO is defined or not, is still not possible after the GCC fix in 2.1.3.

Thanks in advance

[bmcdonnell-fb]

@pedro-fuoco FYI, I have a project using v2.1.2_20190315 (from STM32CubeF4 v1.26.2), in which I'm able to work around the issue by doing #undef LWIP_PROVIDE_ERRNO in lwipopts.h.

I haven't finished updating it yet to see the status on the latest STM32 LwIP.