Re: [kvm-unit-tests BUG] lib/ldiv32.c breaks arm compilation

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/05/21 17:43, Alexandru Elisei wrote:
> Hello,
> 
> Commit 0b2d3dafc0d3 ("libcflat: provide long division routines"), which added the
> lib/ldiv32.c file, breaks compilation for the arm architecture; arm64 seems to be
> working just fine.

The Fedora one is fixed in the commit immediately after, which replaces 
inttypes.h with stdint.h.

For Arch Linux I'm not sure what the compiler is complaining about 
(especially since there are no options such as -fno-null-pointer-checks) 
but perhaps we can just initialize rem to 0?  Any chance you can check 
if that affects the assembly output?  (It shouldn't).

Paolo

> On Arch Linux:
> 
> $ ./configure --arch=arm --cross-prefix=arm-none-eabi-
> $ make clean && make
> rm -f lib/arm/asm-offsets.h lib/arm/asm-offsets.s \
>        lib/generated/asm-offsets.h
> rm -f arm/*.{o,flat,elf} lib/arm/libeabi.a lib/arm/eabi_compat.o \
>        arm/.*.d lib/arm/.*.d
>    CLEAN (libfdt)
> rm -f lib/libfdt/*.o lib/libfdt/.*.d
> rm -f lib/libfdt/libfdt.so.1
> rm -f lib/libfdt/libfdt.a
> rm -f lib/.*.d lib/libcflat.a lib/argv.o lib/printf.o lib/string.o lib/abort.o
> lib/report.o lib/stack.o lib/arm/spinlock.o lib/arm/processor.o lib/arm/stack.o
> lib/ldiv32.o lib/util.o lib/getchar.o lib/alloc_phys.o lib/alloc_page.o
> lib/vmalloc.o lib/alloc.o lib/devicetree.o lib/pci.o lib/pci-host-generic.o
> lib/pci-testdev.o lib/virtio.o lib/virtio-mmio.o lib/chr-testdev.o lib/arm/io.o
> lib/arm/setup.o lib/arm/mmu.o lib/arm/bitops.o lib/arm/psci.o lib/arm/smp.o
> lib/arm/delay.o lib/arm/gic.o lib/arm/gic-v2.o lib/arm/gic-v3.o
> [..]
> arm-none-eabi-gcc -marm -mfpu=vfp -mcpu=cortex-a15 -mno-unaligned-access
> -std=gnu99 -ffreestanding -O2 -I /home/alex/data/repos/kvm-unit-tests/lib -I
> /home/alex/data/repos/kvm-unit-tests/lib/libfdt -I lib -g -MMD -MF lib/.ldiv32.d
> -fno-strict-aliasing -fno-common -Wall -Wwrite-strings -Wempty-body
> -Wuninitialized -Wignored-qualifiers -Werror  -fno-omit-frame-pointer
> -fno-stack-protector    -Wno-frame-address -D__U32_LONG_FMT__  -fno-pic  -no-pie
> -Wclobbered  -Wunused-but-set-parameter  -Wmissing-parameter-type
> -Wold-style-declaration -Woverride-init -Wmissing-prototypes -Wstrict-prototypes
> -c -o lib/ldiv32.o lib/ldiv32.c
> lib/ldiv32.c: In function '__moddi3':
> lib/ldiv32.c:73:11: error: 'rem' may be used uninitialized in this function
> [-Werror=maybe-uninitialized]
>     73 |  uint64_t rem;
>        |           ^~~
> lib/ldiv32.c: In function '__umoddi3':
> lib/ldiv32.c:75:9: error: 'rem' may be used uninitialized in this function
> [-Werror=maybe-uninitialized]
>     75 |  return rem;
>        |         ^~~
> cc1: all warnings being treated as errors
> make: *** [<builtin>: lib/ldiv32.o] Error 1
> $ arm-none-eabi-gcc --version
> arm-none-eabi-gcc (Arch Repository) 10.3.0
> Copyright (C) 2020 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> 
> On Fedora 33:
> 
> $ ./configure --arch=arm --cross-prefix=arm-linux-gnu-
> $ make clean && make
> rm -f lib/arm/asm-offsets.h lib/arm/asm-offsets.s \
>        lib/generated/asm-offsets.h
> rm -f arm/*.{o,flat,elf} lib/arm/libeabi.a lib/arm/eabi_compat.o \
>        arm/.*.d lib/arm/.*.d
>    CLEAN (libfdt)
> rm -f lib/libfdt/*.o lib/libfdt/.*.d
> rm -f lib/libfdt/libfdt.so.1
> rm -f lib/libfdt/libfdt.a
> rm -f lib/.*.d lib/libcflat.a lib/argv.o lib/printf.o lib/string.o lib/abort.o
> lib/report.o lib/stack.o lib/arm/spinlock.o lib/arm/processor.o lib/arm/stack.o
> lib/ldiv32.o lib/util.o lib/getchar.o lib/alloc_phys.o lib/alloc_page.o
> lib/vmalloc.o lib/alloc.o lib/devicetree.o lib/pci.o lib/pci-host-generic.o
> lib/pci-testdev.o lib/virtio.o lib/virtio-mmio.o lib/chr-testdev.o lib/arm/io.o
> lib/arm/setup.o lib/arm/mmu.o lib/arm/bitops.o lib/arm/psci.o lib/arm/smp.o
> lib/arm/delay.o lib/arm/gic.o lib/arm/gic-v2.o lib/arm/gic-v3.o
> [..]
> arm-linux-gnu-gcc -marm -mfpu=vfp -mcpu=cortex-a15 -mno-unaligned-access
> -std=gnu99 -ffreestanding -O2 -I /home/alex/data/repos/kvm-unit-tests/lib -I
> /home/alex/data/repos/kvm-unit-tests/lib/libfdt -I lib -g -MMD -MF lib/.ldiv32.d
> -fno-strict-aliasing -fno-common -Wall -Wwrite-strings -Wempty-body
> -Wuninitialized -Wignored-qualifiers -Werror  -fno-omit-frame-pointer
> -fno-stack-protector    -Wno-frame-address   -fno-pic  -no-pie  -Wclobbered
> -Wunused-but-set-parameter  -Wmissing-parameter-type  -Wold-style-declaration
> -Woverride-init -Wmissing-prototypes -Wstrict-prototypes   -c -o lib/ldiv32.o
> lib/ldiv32.c
> lib/ldiv32.c:1:10: fatal error: inttypes.h: No such file or directory
>      1 | #include <inttypes.h>
>        |          ^~~~~~~~~~~~
> compilation terminated.
> make: *** [<builtin>: lib/ldiv32.o] Error 1
> $ arm-linux-gnu-gcc --version
> arm-linux-gnu-gcc (GCC) 10.2.1 20200826 (Red Hat Cross 10.2.1-3)
> Copyright (C) 2020 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions.  There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> 
> Reverting the commit makes arm build again. I am not familiar with toolchains, and
> unfortunately I can't propose a fix.
> 
> Thanks,
> 
> Alex
>