Can't use RTT with CMake project

[Hyderman]

I tried to use cmake with CubeMx but I cant make RTT works.

Error:

multiple definition of `_write_r'; /usr/lib/gcc/arm-none-eabi/13.2.0/../../../../arm-none-eabi/lib/thumb/v7-m/nofp/libc_nano.a(libc_a-writer.o):/build/arm-none-eabi-newlib/src/build-nano/arm-none-eabi/thumb/v7-m/nofp/newlib/../../../../../../newlib-4.3.0.20230120/newlib/libc/reent/writer.c:45: first defined here

RTT needs to define _write_r but seems already define.

If I comment this line from the gcc tool chain it solves the problem:

set(CMAKE_C_LINK_FLAGS "${CMAKE_C_LINK_FLAGS} -Wl,--start-group -lc -lm -Wl,--end-group")

Before I used my custom cmake this way:
```

target_link_options(${EXECUTABLE} PRIVATE
-T${MCU_LINKER_SCRIPT}
${CPU_PARAMETERS}
-Wl,-Map=${CMAKE_PROJECT_NAME}.map
--specs=nosys.specs
-Wl,--start-group
-lc
-lm
-lstdc++
-Wl,--end-group
-Wl,--print-memory-usage)

```

and have no problem so I don't really understand why.

Also tried -fcommon it does nothing.

[Semer CHERNI]

Hello @Hyderman 

First let me thank you for posting.

Could you share more details about the issue:

• ioc file
• steps done to generate and build the project
• with which environment the build was made

I made a test by generating a CMake project with CubeMX and build it with VSCode and I have a successful build.

KR,
Semer.

[Hyderman]

For example with stm32f103c8t6:

Project manager:

- Copy only necessary files

- Generate peripheral initialization as pair

Toolchain to CMake

Generate code

Adding RTT to CMakeLists.txt:

file(GLOB_RECURSE RTT CONFIGURE_DEPENDS
    ${CMAKE_CURRENT_SOURCE_DIR}/RTT/*c
    ${CMAKE_CURRENT_SOURCE_DIR}/RTT/*S)
add_executable(${CMAKE_PROJECT_NAME}
    ${RTT})

Add necessary files for RTT (see screenshot)

I use a Makefile to call CMake commands but the command to configure is this one:

cmake -GNinja -Bbuild -DPROJECT_NAME=test-cmake -DCMAKE_BUILD_TYPE=Debug

cmake --build build

I am on Linux.

The redefinition of _write_r in the "SEGGER_RTT_Syscalls_GCC.c " file from RTT.

[Ghofrane GSOURI]

Hello @Hyderman 

By seeing the the attached screenshot ,the RTT library is adding GCC syscalls while MX also generate them in a file syscall.c (same for CubeIDE and Makefile) which causes double definition issue.

I believe you need to keep only one syscall to fix the issue.

THX

Ghofrane

[Hyderman]

Hello@Ghofrane GSOURI,

I already tried to remove the syscall.c and in addition the syscall file doesn't define _write_r. If you look at my first message, it's newlib which define _write_r.

If I use my own cmake file, I don't have this problem. It is the way cubemx choses to link to libc which causes this problem but idk why.

[Andrew Neil]

RTT is a proprietary Segger thing - have you tried asking them?

https://forum.segger.com/

[Hyderman]

The problem don't come frome Segger RTT files, it comes from the cmake from cubemx define _write_r while it shouldn't.

RTT needs to define _write_r but newlib define it while it shouldn't.

In itself, it's not a bug. Just wanted the signal that the cmake from cubemx don't work with RTT.

[Andrew Neil]

Sure, but Segger must know about this - the duplicates are coming from standard GCC/ARM libraries with standard GCC/ARM tools.

Segger do like to claim that the work closely with the likes of ST ...

[serg22]

Any update on this ?
Having similar issue, but redefinition happens in libc_nano
SEGGER_RTT_Syscalls_GCC.c:117: multiple definition of `_write_r'; C:/ST/STM32CubeCLT_1.18.0/GNU-tools-for-STM32/bin/../lib/gcc/arm-none-eabi/13.3.1/../../../../arm-none-eabi/lib/thumb/v7e-m+fp/hard\libc_nano.a(libc_a-writer.o):(.text._write_r+0x0): first defined here

[Andrew Neil]

Seems like the previous answers have it all covered:

---

@serg22 wrote:

redefinition happens in libc_nano
SEGGER_RTT_Syscalls_GCC.c:

---

So don't add that file to your Project!

Or remove the syscalls created by CubeMX.