cross compile build for riscv64 fails on Ubuntu 22.04

[maks]

Following the instructions on the wiki I tried building for RISC-V on my x86 (AMD) laptop and this is the error I get is for cross-compiling the SDK for risc-v is:

./tools/build.py --no-goma --no-clang -m release -a riscv64 create_sdk
Done. Made 381 targets from 89 files in 178ms
buildtools/ninja/ninja -C out/ReleaseXRISCV64 create_sdk
ninja: Entering directory `out/ReleaseXRISCV64'
[1851/5076] CXX obj/runtime/vm/libdart_vm_precompiler_product.image_snapshot.o
FAILED: obj/runtime/vm/libdart_vm_precompiler_product.image_snapshot.o 
riscv64-linux-gnu-g++ -MMD -MF obj/runtime/vm/libdart_vm_precompiler_product.image_snapshot.o.d -D_FORTIFY_SOURCE=2 -DNDEBUG -DTARGET_ARCH_RISCV64 -DDART_USE_TCMALLOC -DDART_TARGET_OS_LINUX -DDART_PRECOMPILER -DPRODUCT -DU_USING_ICU_NAMESPACE=0 -DU_ENABLE_DYLOAD=0 -DUSE_CHROMIUM_ICU=1 -DU_ENABLE_TRACING=1 -DU_ENABLE_RESOURCE_TRACING=0 -DU_STATIC_IMPLEMENTATION -DICU_UTIL_DATA_IMPL=ICU_UTIL_DATA_FILE -I../../runtime -I../.. -Igen -I../../runtime/include -I../../third_party/tcmalloc/gperftools/src -I../../third_party/icu/source/common -I../../third_party/icu/source/i18n -fPIC -Wall -Wextra -Werror -Wendif-labels -Wno-missing-field-initializers -Wno-unused-parameter -Wno-ignored-qualifiers -fdebug-prefix-map=/home/maks/builds/dart-sdk/sdk=../.. -no-canonical-prefixes -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -O3 -fno-ident -fdata-sections -ffunction-sections -g3 -ggdb3 -Werror -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field -Wnon-virtual-dtor -Wvla -Woverloaded-virtual -Wno-comments -g3 -ggdb3 -fno-rtti -fno-exceptions -Wno-cast-function-type -O3 -fvisibility=hidden -fvisibility-inlines-hidden -fno-omit-frame-pointer -std=c++17 -fno-rtti -c ../../runtime/vm/image_snapshot.cc -o obj/runtime/vm/libdart_vm_precompiler_product.image_snapshot.o
../../runtime/vm/image_snapshot.cc: In member function ‘virtual void dart::AssemblyImageWriter::ExitSection(dart::ImageWriter::ProgramSection, bool, intptr_t)’:
../../runtime/vm/image_snapshot.cc:1416:27: error: ‘%s’ directive argument is null [-Werror=format-overflow=]
 1416 |   assembly_stream_->Printf(".size %s, %zu\n", SectionSymbol(name, vm), size);
      |   ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../runtime/vm/image_snapshot.cc:1417:27: error: ‘%s’ directive argument is null [-Werror=format-overflow=]
 1417 |   assembly_stream_->Printf(".type %s, %%object\n", SectionSymbol(name, vm));
      |   ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At global scope:
cc1plus: note: unrecognized command-line option ‘-Wno-unused-private-field’ may have been intended to silence earlier diagnostics
cc1plus: all warnings being treated as errors
[1868/5076] CXX obj/runtime/vm/libdart_vm_precompiled_runtime_product.object.o
ninja: build stopped: subcommand failed.
BUILD FAILED

This seems to be newer versions of gcc being more fussy about potential null arguments used in printf.

I followed the instructions to install the risc-v cross-compiler with apt so I have:

/usr/bin/riscv64-linux-gnu-g++ --version
riscv64-linux-gnu-g++ (Ubuntu 11.3.0-1ubuntu1~22.04) 11.3.0

Attempting the same command to compile the native version of the SDK (x64) gives the same error.
Doing so with I assume clang instead of gcc works:

/tools/build.py --no-goma -m release -a x64 create_sdk
Done. Made 348 targets from 90 files in 127ms
buildtools/ninja/ninja -C out/ReleaseX64 create_sdk
ninja: Entering directory `out/ReleaseX64'
[3629/3629] STAMP obj/create_sdk.stamp
The build took 673.270 seconds

But if I attempt to use clang to build for riscv64 I get:

./tools/build.py --no-goma -m release -a riscv64 create_sdk
Done. Made 381 targets from 90 files in 177ms
buildtools/ninja/ninja -C out/ReleaseXRISCV64 create_sdk
ninja: Entering directory `out/ReleaseXRISCV64'
[3/5076] CXX obj/runtime/bin/elf_loader.virtual_memory_fuchsia.o
FAILED: obj/runtime/bin/elf_loader.virtual_memory_fuchsia.o 
../../buildtools/linux-x64/clang/bin/clang++ -MMD -MF obj/runtime/bin/elf_loader.virtual_memory_fuchsia.o.d -DTOOLCHAIN_VERSION=r2G18YIAK34NbwRXt2sm5ZlMA0QhhvPDqM5Ccy24kRQC -DNDEBUG -DTARGET_ARCH_RISCV64 -DDART_USE_TCMALLOC -DPRODUCT -DDART_TARGET_OS_FUCHSIA -I../../runtime -I../.. -Igen -I../../runtime/include -I../../third_party/tcmalloc/gperftools/src -fPIC --target=riscv64-linux-gnu -fcolor-diagnostics -Wall -Wextra -Werror -Wendif-labels -Wno-missing-field-initializers -Wno-unused-parameter -Wno-tautological-constant-compare -Wno-unused-but-set-variable -Wno-deprecated-non-prototype -fdebug-prefix-map=/home/maks/builds/dart-sdk/sdk=../.. -no-canonical-prefixes -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -Wheader-hygiene -Wstring-conversion -O3 -fno-ident -fdata-sections -ffunction-sections -g3 -ggdb3 -Werror -Wall -Wextra -Wno-unused-parameter -Wno-unused-private-field -Wnon-virtual-dtor -Wvla -Woverloaded-virtual -Wno-comments -g3 -ggdb3 -fno-rtti -fno-exceptions -Wimplicit-fallthrough -fno-strict-vtable-pointers -O3 -fvisibility=hidden -fvisibility-inlines-hidden -fno-omit-frame-pointer -std=c++17 -fno-rtti -c ../../runtime/bin/virtual_memory_fuchsia.cc -o obj/runtime/bin/elf_loader.virtual_memory_fuchsia.o
In file included from ../../runtime/bin/virtual_memory_fuchsia.cc:5:
In file included from ../../runtime/platform/globals.h:80:
In file included from ../../buildtools/linux-x64/clang/bin/../include/c++/v1/float.h:73:
../../buildtools/linux-x64/clang/bin/../include/c++/v1/__config:13:10: fatal error: '__config_site' file not found
#include <__config_site>
         ^~~~~~~~~~~~~~~
1 error generated.

So is there a specific version of gcc I should be using for cross compiling for riscv64 ?

[kevmoo]

CC @rmacnak-google