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glaucus

mlibc

  • Replaces musl
  • Depends on frigg which optionally depends on gtest and mimalloc
  • -Duse_freestnd_hdrs=enabled is required for frigg to properly include its headers given that -nostdinc is being passed
  • Requires -Dwrap_mode=nodownload be removed as it pulls frigg and the freestanding headers when building which renders the build not fully offline
  • Does not support -z,now
  • Depends on static libgcc.a for __mulsc3 and __muldc3 for x86-64 (even with -Dlibgcc_dependency=false)
  • gcc does not recognize mlibc without updating config.sub

Experiments with mlibc version 6.3.1

Section titled “Experiments with mlibc version 6.3.1”
  • The following tuple was used x86_64-linux-mlibc for both host and target; mlibc is already niche enough to drive gcc into thinking we are cross-compiling which did not require an x86_64-glaucus-linux-mlibc tuple
  • Both rad and meson.cross were updated to use the above tuple
  • Build order:
Terminal window
linux-headers # required as mlibc-headers include headers from the kernel)


mlibc-headers
  "$core"/muon/files/glaucus-meson \
  --cross-file="$core"/muon/files/meson.cross \
    -Dheaders_only=true \
    -Dlinux_kernel_headers="$cross/usr/include" \
    build-headers


binutils
gcc
  # required passing `--disable-libgomp` and disabling most of `libstdcxx` options to build
  # for static libgcc, `CFLAGS_FOR_TARGET="-pipe -O0 -I$cross/usr/include"` was passed


mlibc
  LDFLAGS="-Wl,$toolchain/lib/gcc/$host/15.2.0/libgcc.a" \
  "$core"/muon/files/glaucus-meson \
    --cross-file="$core"/muon/files/meson.cross \
    -Dno_headers=true \
    -Dlibgcc_dependency=false \
    -Dlinux_kernel_headers="$cross/usr/include" \
    -Duse_freestnd_hdrs=enabled \
    -Dld_library_name=ld-linux-$nom \
    build


libgcc
libstdc++-v3
  • The following were patched to support mlibc:
gcc/config/linux.h
gcc/config.gcc
libstdc++-v3/config/os/gnu-linux/os_defines.h
libstdc++-v3/configure
  • Requires updating the config.subs of every project being built for now to recognize mlibc
  • Breakages early on in cross with netbsd-curses and skalibs
  • Large libc.so size 4.2 M after toolchain is built (compared to musl)
  • Very promising compared to other alternative C libraries, but not ready yet

References

Section titled “References”