Include extenal C runtime files in the CMake flow

[danivz]

The current CMake software compilation flow doesn't support external C runtime files.

Following the instructions in eXtending_HEEP.md I have:

BASE
    └── sw
        ├── applications
        │   └── your_app
        │       ├── main.c
        │       ├── your_app.c
        │       ├── your_app.h
        │       └── ...
        ├── build -> ../hw/vendor/esl_epfl_x_heep/sw/build
        ├── device -> ../hw/vendor/esl_epfl_x_heep/sw/device
        ├── linker -> ../hw/vendor/esl_epfl_x_heep/sw/linker
        └── external
            └── lib
                ├── crt
                |   └── external_crt0.S
                └── drivers
                │       └── fll
                |           └── fll_regs.h
                └── runtime
                    └── heepie.h

I want to include external_crt0.S in https://github.com/esl-epfl/x-heep/blob/8f2351053dd240d4e6a01ac90cfcd49fb78a747c/sw/CMakeLists.txt#L169C1-L172C37. However, If I hardcode the CRT file path in LINKED_FILES the compilation fails because fll_regs.h and heepie.h are included in external_crt0.S and the compiler can't find these headers.

I also noticed that in crt0.S the macro EXTERNAL_CRT0 isn't set automatically when there is a external CRT file: https://github.com/esl-epfl/x-heep/blob/8f2351053dd240d4e6a01ac90cfcd49fb78a747c/sw/device/lib/crt/crt0.S#L44C1-L46C7

[davideschiavone]

Well catched, this function should be restored asap

[JuanSapriza]

After these lines in the CMakeLists.txt

SET(LIB_CRT_P	"${SOURCE_PATH}device/lib/crt/")
SET(LIB_VCTR_P	"${LIB_CRT_P}vectors.S")

We should be considering whether the application is an external app.
This should be done by comparing the EXPANDED SOURCE_PATH against the EXPANDED ROOT_PROJECT.

with expanded i mean the absolute path

If both paths are equal, then the app is internal, if not, its external.

Once you have determined that, we should include an external_crt0.s and external_vetor.S if they exist (an not the default ones).

---

The EXTERNAL_CRT0 should be added in

# specify the C standard
set(COMPILER_LINKER_FLAGS "\
  -march=${CMAKE_SYSTEM_PROCESSOR} \
  -w -Os -g  -nostdlib  \
  -DHOST_BUILD \
  -D${CRT_TYPE} \
  -DportasmHANDLE_INTERRUPT=vSystemIrqHandler\
")

[JoseCalero]

This should be fixed and closed due to #358

[davideschiavone]

@danivz , can you please close this issue and tell us if the solution works?

[JuanSapriza]

@JoseCalero you sure #358 would fix this? It did not implement what we discussed in this comment

[JoseCalero]

You are right, we are missing the external, I will do it asap

[JuanSapriza]

Being fixed in #364