vlibc

A modern replacement for glibc: a performant, standard-conforming C library with modern extensions and high glibc compatibility.

vlibc is written in C (C23, with C2y/C29 opt-in), built with Autotools and a single compiler (GCC, no fallback). Full static linking is a first-class, required capability.

Capabilities

• Five compatibility profiles, from the lightest to the most compatible:
  1. --enable-onlyposix — pure POSIX, nothing more.
  2. --enable-muslmimic — musl-like, light and musl-compatible.
  3. --enable-muslext — musl-extended.
  4. --enable-spoof — a glibc replica, for drop-in compatibility with scripts and programs that rely on long-standing glibc behavior.
  5. (default) — vlibc: glibc-extended, without the spoofing layer, but with extended standard features and high glibc compatibility.
• Two install methods (--with-install=):
  • alongside (default) — install next to the system libc, under a vlibc-specific tree; the system libc is left untouched.
  • overwrite — replace the system libc in place.
• vlibc-gcc and vlibc-clang compiler drivers, so consuming projects build against vlibc with either compiler.
• Full static linking is required for every profile except spoof.
• Compiler intent is declared on the public API (e.g. __attribute__((const))) so the compiler can fold and eliminate calls, keeping statically linked binaries small.

Build

./autogen.sh                 # regenerate build system + configure
make                          # build
make debug                    # build with -O0 -g3 into bin/debug/
make release                  # build with -O3 into bin/release/
make bench                    # build and run benchmarks
make clean                    # remove build artifacts
make compile-commands         # regenerate compile_commands.json (needs bear)

Common configure options:

./autogen.sh --enable-spoof                     # glibc replica profile
./autogen.sh --with-install=overwrite           # replace system libc
./autogen.sh --with-libc=glibc                  # benchmark against glibc
./autogen.sh --enable-c29                       # experimental C2y (C29)

User-provided CFLAGS and LDFLAGS are honored.

Layout

include/        public headers (mandatory)
src/            implementation sources
benchmarks/     benchmark harnesses (vs. glibc/musl)
docs/           behavior and glibc-difference documentation
thirdparty/     vendored third-party libraries
tools/          vlibc-gcc / vlibc-clang driver templates
bin/{release,debug}/  build outputs

Documentation

• docs/overview.md — what vlibc is and how it behaves.
• docs/compatibility.md — the five profiles and glibc differences.
• docs/install.md — the two install methods.
• CONTRIBUTING.md — how to contribute.
• STYLEGUIDE.md — how code should look.