Building apps with gcc flag '-mhard-float' ?

Hello 🦀,

I measured the execution time of the same C nbody benchmark program on top of FreeRTOS & Tock.
(I only modified variable n in the main function to be const volatile int n = 50000;)
(Both cases were tested on NucleoF429ZI board)

• nbody on FreeRTOS : 13.037325 seconds
• nbody on Tock : 360.536 seconds

I found that Tock apps are currently built with gcc flag -mfloat-abi=soft
https://github.com/tock/libtock-c/blob/3d96d35efab0f48c6f491951be62d69a67a394c8/Configuration.mk#L138
I tried replacing the flag with -mfloat-abi=hard,
but I received the following error.

lonelyjoe@lonelyjoe-desktop:~/workspace/libtock-c/examples/n-body$ make
  CC        main.c
In file included from ./../../support/warning_header.h:6:0,
                 from <command-line>:0:
/usr/include/newlib/stdio.h: In function '__sputc_r':
/usr/include/newlib/stdio.h:671:39: sorry, unimplemented: Thumb-1 hard-float VFP ABI
 _ELIDABLE_INLINE int __sputc_r(struct _reent *_ptr, int _c, FILE *_p) {
                                       ^~~~~~

On Stm32CubeIDE which provides newlib-nano as the default runtime library,
I had no errors while building the same C program on top of FreeRTOS with the -mfloat-abi=hard configuration.
One thing I see is that the instruction set I used in stm32cubeide was Thumb-2,
while the error from building Tock tells me Thumb-1 hard-float VFP ABI is not implemented.

(below is an image of the build configuration I used for building nbody on FreeRTOS)

Is there a way to work around this error to build apps with flag -mfloat-abi=soft?
Or is it currently possible to use Thumb-2 instruction set instead of Thumb-1?

Thank you for checking out this issue 👍 👍

Start with Configuration.mk at the cited flag definition and reproduce the build from examples/n-body using the reported command and NucleoF429ZI target. Compare the configured ABI and instruction-set options with the compiler error, then establish whether a supported build configuration or a documented limitation is needed.