lwIP, linker error with PPP enabled

[TheRealZago]

When compiling a basic application with PPP enabled and support for authentication (PAP, CHAP and friends), the linker fails with the following error:

/Applications/ArmGNUToolchain/13.3.rel1/arm-none-eabi/bin/../lib/gcc/arm-none-eabi/13.3.1/../../../../arm-none-eabi/bin/ld: CMakeFiles/PicoModem.dir/Users/zago/repo/pico-sdk/lib/lwip/src/netif/ppp/magic.c.o: in function `magic_churnrand':
[build] /Users/zago/repo/pico-sdk/lib/lwip/src/netif/ppp/magic.c:118:(.text.magic_churnrand+0x30): undefined reference to `sys_jiffies'

My lwipopts.h is loosely based on the file provided by the pico_w examples, with just a few additions:

#define NO_SYS 1
// ... omissis ...
#define PPP_SUPPORT 1
#define PAP_SUPPORT 1
#define CHAP_SUPPORT 1
#define MSCHAP_SUPPORT 1
#define PPP_SERVER 1

"HAL" is being provided by linking against pico_lwip_nosys.

Workaround

I've noticed pico_lwip_nosys already defines sys_now(), so I've exteded its job by adding my own library hook function in a dedicated source file.

// @file libhooks.c

#include "lwip/sys.h"
#include "hardware/timer.h"

u32_t sys_jiffies(void)
{
    return time_us_32();
}

Should I open a pull request with a cleaner SDK-side correction?

[kilograham]

sounds good

[peterharperuk]

You might have to wrap it with #if NO_SYS as sys_jiffies is defined for free rtos? And maybe have another way of disabling it in case someone has their own implementation.

[kilograham]

I think you can just put __weak on it; chances are that no one else has implemented it but still. this would go in already guarded code in lwip_nosys.c so should be fine

[kilograham]

fix merged into develop