Summary

NuttX Build fails when it compiles examples/hello_nim for RISC-V (32-bit and 64-bit). That's because the Nim Config Script config.nims couldn't identify the Nim Target Platform: riscv32 or riscv64.

This PR fixes config.nims so that Nim Compiler correctly derives the Nim Target Platform (riscv32 or riscv64), by searching NuttX .config for CONFIG_ARCH_FAMILY=rv32 or rv64.

This logic is slightly different from the Nim Targets arm and arm64, which are currently derived from CONFIG_ARCH=arm and arm64.

config.nims is explained in this article.

Impact

With this PR, Nim Apps will build correctly for 32-bit and 64-bit RISC-V.

There is no impact on other platforms, like Arm and Arm64.

Testing

We tested by building QEMU NuttX with examples/hello_nim enabled for RISC-V 32-bit, RISC-V 64-bit and Arm64 (for regression testing).

RISC-V 32-bit

Before Fixing: NuttX Build fails for hello_nim because arch and cpu in Nim Compiler are empty:

$ tools/configure.sh rv-virt:nsh
$ kconfig-tweak --enable CONFIG_EXAMPLES_HELLO_NIM
$ make
* arch:    
/workspaces/bookworm/apps/config.nims(1, 2)
Error: argument for command line option expected: '--cpu'

(Failed Build Log for 32-bit RISC-V)

After Fixing: NuttX Build succeeds with the correct arch and cpu in Nim Compiler:

$ make
* arch:    riscv32
Hint: used config file '/workspaces/bookworm/apps/config.nims' [Conf]

(Fixed Build Log for 32-bit RISC-V)

RISC-V 64-bit

NuttX Build succeeds with the correct arch and cpu in Nim Compiler:

$ tools/configure.sh rv-virt:nsh64
$ kconfig-tweak --enable CONFIG_EXAMPLES_HELLO_NIM
$ make
* arch:    riscv64
Hint: used config file '/workspaces/bookworm/apps/config.nims' [Conf]

(Fixed Build Log for 64-bit RISC-V)

Arm64

For Regression Testing: NuttX Build succeeds with the correct arch and cpu in Nim Compiler:

$ tools/configure.sh qemu-armv8a:nsh
$ kconfig-tweak --enable CONFIG_EXAMPLES_HELLO_NIM
$ make
* arch:    arm64
Hint: used config file '/workspaces/bookworm/apps/config.nims' [Conf]

(Build Log for Arm64)

Nim Exception

For Arm64: hello_nim runs correctly on Arm64 QEMU:

nsh> hello_nim
Hello from task 1! loops: 0
Hello from task 2! loops: 0
...
Hello from task 3! loops: 2

(NuttX Log for Arm64)

For RISC-V 32-bit and 64-bit: hello_nim halts with a Load Access Fault for 32-bit RISC-V:

nsh> hello_nim
Hello from task 1! loops: 0
riscv_exception: EXCEPTION: Load access fault. MCAUSE: 00000005, EPC: 8000dd10, MTVAL: 00000038

Load Access Fault at nuttx/fs/inode/fs_files.c:607
  /* if f_inode is NULL, fd was closed */
  if ((*filep)->f_inode == NULL)
8000dd10:	451c                	lw	a5,8(a0)

(NuttX Exception for 32-bit RISC-V)

hello_nim also halts with a Load Access Fault for 64-bit RISC-V:

nsh> hello_nim
Hello from task 1! loops: 0
riscv_exception: EXCEPTION: Load access fault. MCAUSE: 0000000000000005, EPC: 0000000080002432, MTVAL: d0ef000555638482

Load Access Fault at nuttx/sched/semaphore/sem_wait.c:93
nxsem_wait():
  /* Make sure we were supplied with a valid semaphore. */
  /* Check if the lock is available */
  if (sem->semcount > 0)
    80002432:	00055783          	lhu	a5,0(a0)

(NuttX Exception for 64-bit RISC-V)

This will be fixed later. For now, we tested a Simple Nim Function that runs correctly on 32-bit and 64-bit RISC-V:

## Simple Nim Function that prints something
$ cat ../apps/examples/hello_nim/hello_nim_async.nim
proc hello_nim() {.exportc, cdecl.} =
  echo "Hello Nim!"
  GC_runOrc()

$ make
$ qemu-system-riscv32 \
  -M virt,aclint=on \
  -cpu rv32 \
  -smp 8 \
  -bios none \
  -kernel nuttx \
  -nographic

NuttShell (NSH) NuttX-12.0.3
nsh> hello_nim
Hello Nim!

(Simple Nim Log for 32-bit RISC-V)

(Simple Nim Log for 64-bit RISC-V)