Compilation of examples fails because of inapplicable autoconf checks.

[Ma124]

The compilation of the examples fails even after manually dealing with #574 because autoconf tries to run some sanity checks on the compiler.

It tries to compile the following code:

/* confdefs.h */
#define PACKAGE_NAME "freedom-metal"
#define PACKAGE_TARNAME "freedom-metal"
#define PACKAGE_VERSION "v0.1.2"
#define PACKAGE_STRING "freedom-metal v0.1.2"
#define PACKAGE_BUGREPORT "https://github.com/sifive/freedom-metal/issues"
#define PACKAGE_URL "https://github.com/sifive/freedom-metal"
#define PACKAGE "freedom-metal"
#define VERSION "v0.1.2"
/* end confdefs.h.  */

int
main ()
{

  ;
  return 0;
}

Without -nostdlib it fails because the linker cannot find some objects:

$ riscv64-unknown-elf-gcc test.c
/usr/lib/gcc/riscv64-unknown-elf/9.2.0/../../../../riscv64-unknown-elf/bin/ld: cannot find crt0.o: No such file or directory
/usr/lib/gcc/riscv64-unknown-elf/9.2.0/../../../../riscv64-unknown-elf/bin/ld: cannot find -lc
/usr/lib/gcc/riscv64-unknown-elf/9.2.0/../../../../riscv64-unknown-elf/bin/ld: cannot find -lgloss
collect2: error: ld returned 1 exit status

Failure with -nostdlib

This fails because riscv64-unknown-elf-gcc cannot find the _start symbol required by bare metal targets.

GCC command to test this

$ cat << 'EOF' > test.c
/* confdefs.h */
#define PACKAGE_NAME "freedom-metal"
#define PACKAGE_TARNAME "freedom-metal"
#define PACKAGE_VERSION "v0.1.2"
#define PACKAGE_STRING "freedom-metal v0.1.2"
#define PACKAGE_BUGREPORT "https://github.com/sifive/freedom-metal/issues"
#define PACKAGE_URL "https://github.com/sifive/freedom-metal"
#define PACKAGE "freedom-metal"
#define VERSION "v0.1.2"
/* end confdefs.h.  */

int
main ()
{

  ;
  return 0;
}
EOF

$ riscv64-unknown-elf-gcc -nostdlib -march=rv32imac -mabi=ilp32 test.c
/usr/lib/gcc/riscv64-unknown-elf/9.2.0/../../../../riscv64-unknown-elf/bin/ld: warning: cannot find entry symbol _start; defaulting to 0000000000010054

I have tried circumventing this by including _start in all test source files using the following sed command:

sed -i 's/int$/int main();\nvoid _start() {main();}\nint/g' freedom-metal/configure

That didn't work either.

After that I stopped configure from aborting on errors and just let it continue by changing as_fn_error in line 410 of freedom-metal/configure.
This approach failed because autoconf extracts information from the build process such as the file extension of executable and object files.

Make command to test this

$ make software                                                   
cd /home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug/ && \
	CFLAGS="-march=rv32imac -mabi=ilp32 -mcmodel=medlow -ffunction-sections -fdata-sections -I/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/install/include --specs=nano.specs -DMTIME_RATE_HZ_DEF=32768 -O0 -g" \
	/home/ma/src/sifive/freedom-e-sdk/freedom-metal/configure \
	--host=riscv64-unknown-elf \
	--prefix=/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/install \
	--libdir=/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/install/lib/debug \
	--with-builtin-libgloss \
	--with-machine-header=/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/metal.h \
	--with-machine-inline=/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/metal-inline.h \
	--with-platform-header=/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/metal-platform.h
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for riscv64-unknown-elf-strip... riscv64-unknown-elf-strip
checking for a thread-safe mkdir -p... /usr/bin/mkdir -p
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking whether to enable maintainer-specific portions of Makefiles... no
checking build system type... x86_64-pc-linux-gnu
checking host system type... riscv64-unknown-elf
checking for riscv64-unknown-elf-gcc... riscv64-unknown-elf-gcc
checking whether the C compiler works... no
configure: error: in `/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug':
configure: error: C compiler cannot create executables
See `config.log' for more details
checking for C compiler default output file name... 
checking for suffix of executables... configure: error: in `/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug':
configure: error: cannot compute suffix of executables: cannot compile and link
See `config.log' for more details

checking whether we are cross compiling... yes
checking for suffix of object files... configure: error: in `/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug':
configure: error: cannot compute suffix of object files: cannot compile
See `config.log' for more details

checking whether we are using the GNU C compiler... no
checking whether riscv64-unknown-elf-gcc accepts -g... no
checking for riscv64-unknown-elf-gcc option to accept ISO C89... unsupported
checking whether riscv64-unknown-elf-gcc understands -c and -o together... yes
checking for style of include used by make... GNU
checking dependency style of riscv64-unknown-elf-gcc... gcc3
checking for riscv64-unknown-elf-ranlib... riscv64-unknown-elf-ranlib
checking for riscv64-unknown-elf-ar... riscv64-unknown-elf-ar
checking the archiver (riscv64-unknown-elf-ar) interface... ar
checking dependency style of riscv64-unknown-elf-gcc... gcc3
configure: error: in `/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug':
configure: error: The C compiler doesn't define __riscv, which means it's probably not a RISC-V compiler.  You should specify something like --host=riscv64-sifive-elf when building this, as it will only work on RISC-V systems.
See `config.log' for more details
checking that generated files are newer than configure... done
configure: creating ./config.status
config.status: creating Makefile
config.status: executing depfiles commands
touch -c /home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug/Makefile
make -C /home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug install
make[1]: Entering directory '/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug'
cp /home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/metal.h metal/machine.h
cp /home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/metal-inline.h metal/machine/inline.h
cp /home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/metal-platform.h metal/machine/platform.h
make  install-am
make[2]: Entering directory '/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug'
rm -f libmetal.a
riscv64-unknown-elf-ar cru libmetal.a src/drivers/fixed-clock. src/drivers/fixed-factor-clock. src/drivers/inline. src/drivers/riscv_clint0. src/drivers/riscv_cpu. src/drivers/riscv_plic0. src/drivers/sifive_buserror0. src/drivers/sifive_ccache0. src/drivers/sifive_clic0. src/drivers/sifive_fe310-g000_hfrosc. src/drivers/sifive_fe310-g000_hfxosc. src/drivers/sifive_fe310-g000_lfrosc. src/drivers/sifive_fe310-g000_pll. src/drivers/sifive_fe310-g000_prci. src/drivers/sifive_global-external-interrupts0. src/drivers/sifive_gpio-buttons. src/drivers/sifive_gpio-leds. src/drivers/sifive_gpio-switches. src/drivers/sifive_gpio0. src/drivers/sifive_i2c0. src/drivers/sifive_l2pf0. src/drivers/sifive_local-external-interrupts0. src/drivers/sifive_pwm0. src/drivers/sifive_rtc0. src/drivers/sifive_spi0. src/drivers/sifive_test0. src/drivers/sifive_trace. src/drivers/sifive_uart0. src/drivers/sifive_simuart0. src/drivers/sifive_wdog0. src/drivers/ucb_htif0. src/atomic. src/button. src/cache. src/clock. src/cpu. src/entry. src/scrub. src/trap. src/gpio. src/hpm. src/i2c. src/init. src/interrupt. src/led. src/lock. src/memory. src/pmp. src/privilege. src/pwm. src/rtc. src/shutdown. src/spi. src/switch. src/synchronize_harts. src/timer. src/time. src/trap. src/tty. src/uart. src/vector. src/watchdog. 
riscv64-unknown-elf-ar: `u' modifier ignored since `D' is the default (see `U')
riscv64-unknown-elf-ar: src/drivers/fixed-clock.: No such file or directory
make[2]: *** [Makefile:890: libmetal.a] Error 1
make[2]: Leaving directory '/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug'
make[1]: *** [Makefile:1287: install] Error 2
make[1]: Leaving directory '/home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/build/debug'
make: *** [scripts/libmetal.mk:124: /home/ma/src/sifive/freedom-e-sdk/bsp/freedom-e310-arty/install/lib/debug/stamp] Error 2

I no longer have any ideas how to proceed, but this needs investigation by someone with a better knowledge of autoconf.

This is probably the same issue as riscv-pk#7.

I am using Arch Linux and obtained riscv64-unknown-elf-gcc from the AUR, compilation options of gcc can be found here.