Hi. I'm using GCC to target an ARM (XScale) processor. I've
successfully built code that runs on the target hardware, but I'm
trying to understand better some of the nuances.
I should point out that I've asked this question on the GNUARM list
and gotten no responses.
I have a very simple situation. A single main.c and start.S are
compiled, then linked using ld, then stripped with objcopy and
finally downloaded to the target. However, if I add -march=armv5te, I
get a very puzzling error. Here are the basic invocations:
$ arm-elf-gcc -c main.c -o main.o
$ arm-elf-ld -e _start -o h.elf --script=link.lds start.o main.o
$ arm-elf-objcopy --output-target=binary --gap-fill=0xff h.elf h
The resulting file "h" works very well.
However, if I add -mcpu=xscale or -march=armv5te to the gcc line, I
get errors like this:
arm-elf-ld: ERROR: main.o uses VFP instructions, whereas h.elf does not
What's puzzling to me about this is that h.elf is what's being built
by ld. Presumably there's an option to ld to make it recognize the
architecture, but I'm not sure what it is. I tried to change the
build steps to call gcc instead of ld, as follows (although I'm not
at all sure this is the correct approach):
$ arm-elf-gcc -ffreestanding -nostdlib -std=c99 \
-Xlinker -e -Xlinker _start -Xlinker --script=link.lds \
-v -o h.elf start.o main.o
Which seems to have produced the exact same final output (after
objcopy). However, when I added -march=armv5e to the gcc invocations,
I still get the error about VFP instructions.
I sure hope there's a GCC guru out there who can enlighten me. Thanks!
--
Rick
