D Apps for Apache NuttX RTOS and QEMU RISC-V

upstream PR: apache/nuttx#12457 [MERGED]

Inspired in Rust Apps for Apache NuttX RTOS and QEMU RISC-V by Lup Yuen Lee.

Read https://lupyuen.github.io/articles/rust3

How to work

• Get nuttx and nuttx-apps

git clone --depth=1 --recursive https://github.com/apache/nuttx -b nuttx-12.5.1
git clone --depth=1 --recursive https://github.com/apache/nuttx-apps -b nuttx-12.5.1 apps
# optional (kconfig-frontends) build or use your distro pkg-manager
git clone  --depth=1 https://bitbucket.org/nuttx/tools.git

• apply patches
• build nuttx
• Output

qemu-system-riscv32 \
    -semihosting \
    -M virt,aclint=on \
    -cpu rv32 -smp 8 \
    -bios none \
    -kernel nuttx -nographic
nsh> hello_d
Hello World, [generic-rv32]!
hello_d_main: Saying hello from the dynamically constructed instance
DHelloWorld.HelloWorld: CONSTRUCTION FAILED!
hello_d_main: Saying hello from the instance constructed on the stack
DHelloWorld.HelloWorld: Hello, World!!

Notes

During some tests you may discover druntime (if used) and the compiler builtin require libunwind. There are some common errors to work around (not just in rv32/64).

• need static keyword (TLS) - use --emulated-tls.
• like C/C++ custom #ifdef/ifndef FOO (-DFOO=1) to Version(Foo) (--d-version=Foo)
• verbose/tips keywords:
  • -vgc: list all gc allocations including hidden ones (if use DRT/GC alloc)
  • -vtls: list all variables going into TLS (thread local storage)
  • -verrors=context: show error messages with the context of the erroring source line (show LoC error)

--- a/examples/hello_d/Makefile
+++ b/examples/hello_d/Makefile
@@ -26,7 +26,10 @@ MAINSRC = hello_d_main.d
 
 # hello_d built-in application info
 
-DFLAGS += -oq -betterC
+DFLAGS += -oq -betterC -vtls --emulated-tls
+DFLAGS += -verrors=context -O
+DFLAGS += --d-version=NuttX_D_Initialize

NuttX dlang-app supports betterC mode only?

Official DRT(D runtime) isn't ideal for embedded (particularly microcontrollers). However, it's possible make your own mini/tiny DRT, like:

• https://github.com/KitsunebiGames/tinyd-rt (used on D_on_Dreamcast)
• How to work custom Druntime - by Adam D. Ruppe - my fork updated