fix link problem (no error but code size was 0).
[target.thumbv7m-none-eabi]
# uncomment this to make `cargo run` execute programs on QEMU
-runner = "qemu-system-arm -cpu cortex-m3 -machine lm3s6965evb -semihosting-config enable=on,target=native -nographic -kernel"
+runner = "qemu-system-arm -cpu cortex-m3 -machine lm3s6965evb -nographic -semihosting-config enable=on,target=native -kernel"
+
+[target.'cfg(all(target_arch = "arm", target_os = "none"))']
+# uncomment ONE of these three option to make `cargo run` start a GDB session
+# which option to pick depends on your system
+# runner = "arm-none-eabi-gdb -q -x openocd.gdb"
+# runner = "gdb-multiarch -q -x openocd.gdb"
+# runner = "gdb -q -x openocd.gdb"
+
+rustflags = [
+ # LLD (shipped with the Rust toolchain) is used as the default linker
+ "-C", "link-arg=-Tlink.x",
+
+ # if you run into problems with LLD switch to the GNU linker by commenting out
+ # this line
+ # "-C", "linker=arm-none-eabi-ld",
+
+ # if you need to link to pre-compiled C libraries provided by a C toolchain
+ # use GCC as the linker by commenting out both lines above and then
+ # uncommenting the three lines below
+ # "-C", "linker=arm-none-eabi-gcc",
+ # "-C", "link-arg=-Wl,-Tlink.x",
+ # "-C", "link-arg=-nostartfiles",
+]
\ No newline at end of file
