The handle_trap function is used internally by the trap_entry
implementation from the same file. However, the trap_entry
implementation calls handle_trap from inline assembly. This makes it
difficult for the compiler to infer that the handle_trap function is
used at all. This causes issues when LTO is enabled.
Without this patch compiling any RISC-V RIOT code with `LTO=1` causes
the following linker error:
/home/soeren/src/RIOT/cpu/riscv_common/irq_arch.c:134: undefined reference to `handle_trap'
/tmp/hello-world.elf.Nngidp.ltrans0.ltrans.o:cpu/riscv_common/irq_arch.c:134:(.text.trap_entry+0x34):
relocation truncated to fit: R_RISCV_GPREL_I against undefined symbol `handle_trap'
This commit fixes LTO support for RISC-V.
While at it, also mark the function as static as it is only used by the
trap_entry function from the same compilation unit.
read_csr() returns an unsigned long, not a uint32_t. This causes a
-Wformat warning to be emitted when compiling with clang. This commit
fixes the warning by changing the format string.
This requires -nostartfiles to be only passed to the linker, not the
compiler, as it is a linker flag and passing it to the compiler causes a
clang warning to be emitted.
Additionally, clang does not seem to support `-mcmodel=medlow` and
`-msmall-data-limit=8` but these options do not seem strictly necessary
to me anyhow thus they are deactivated conditionally when using clang.
