Add clang to compiler.h

[Ryzee119]

Describe the PR
I'm using the clang compiler which for our purposes the compiler attributes match GCC from what I can read.

Although TU_ATTR_WEAK had to be changed to __attribute__ ((weak_import)) or I was getting lld: error: duplicate symbol errors on all the TU_ATTR_WEAK functions.

[hathach]

can you do the #ifdef #else instead of undef (ust move this up). undef is rather confusing since people may only look at the first define.

[Ryzee119]

Just to clarify @hathach

Like this?

#if defined(__GNUC__) || defined (__clang__)
  #define TU_ATTR_ALIGNED(Bytes)        __attribute__ ((aligned(Bytes)))
  #define TU_ATTR_SECTION(sec_name)     __attribute__ ((section(#sec_name)))
  #define TU_ATTR_PACKED                __attribute__ ((packed))
  #if defined(__GNUC__)
    #define TU_ATTR_WEAK                  __attribute__ ((weak))
  #else
    #define TU_ATTR_WEAK                  __attribute__ ((weak_import))
  #endif
... 
...

[hathach]

yeah, but the otherway around

  #if defined(__clang__)
    #define TU_ATTR_WEAK                  __attribute__ ((weak_import))
  #else
    #define TU_ATTR_WEAK                  __attribute__ ((weak))
  #endif

[Ryzee119]

All fixed :)
Not sure why pre-commit CI is failing 🤔

[hathach]

unit test probably compile using clang, and has affected by this attribute. I will check later.

[hathach]

still haven't got time to test this out, will be off for a couple of week for TET holidays. Please be patient, thank you.

[hathach]

@Ryzee119 I am back from TET holidays, which compiler you are using. If it is arm clang, I could give it a try (was planning to support it anwyay).

[hathach]

recently I switch to use weak as the default implementation of callback to be compatible with keil #2239

https://github.com/hathach/tinyusb/blob/master/src/device/usbd.c#L48

the other callback header can work with weak_import, but this style seems to require actual weak and cause the compile issue with unit-test (since test include mocking of dcd layer).

Maybe I should use weakref/alias or unify them all to default implemenation, will revise later. We probably need to keep this open until then. Thank you.

[HiFiPhile]

How it goes with #2606 ?