chlibc

A lightweight 64-bit Linux userspace tool that lets you run any dynamically linked program with a custom glibc (Conda, custom build, or alternate sysroot). It uses ptrace to transparently replace the dynamic linker (PT_INTERP) and libc at every execve — no containers, no binary patching, no LD_* env hacks.

Runtime Kernel Requirements

Architecture	Minimum Kernel Version
x86_64 (X64)	Linux >= 2.6.18
AMD64	Linux >= 3.19
RISC-V 64	Linux >= 5.4

Usage

Basic usage:

chlibc <target_program> [args...]

Path Configuration

Three paths control chlibc's behavior, auto-discovered in priority order:

Path	Variable	Fallback Chain	Purpose
Interpreter	CHLIBC_INTERP	CHLIBC_GLIBC_HOME → CONDA_PREFIX → dirname($0)/../<arch>/sysroot	Target dynamic linker (ld.so).
GLIBC Home	CHLIBC_GLIBC_HOME	CONDA_PREFIX → dirname(CHLIBC_INTERP) → dirname($0)/../<arch>/sysroot	Custom glibc root directory. Injected as first entry in LD_LIBRARY_PATH.
Prefix / Scope	CHLIBC_PREFIX	CONDA_PREFIX → dirname($0)/..	Replacement scope limit. Only binaries under this path (/proc/<pid>/exe) are intercepted.

Environment Variables

Variable	Description
CONDA_PREFIX	Auto-detects everything (recommended)
CHLIBC_INTERP	Path to target dynamic linker (e.g. ld-linux-x86-64.so.2)
CHLIBC_GLIBC_HOME	Root directory of custom glibc
CHLIBC_PREFIX	Only replace when binary is under this path
CHLIBC_LOGGER_FILE	Path to log file. If unset, defaults to stderr (if TTY) or syslog fallback.

Example

export CONDA_PREFIX=/opt/conda/envs/myenv
chlibc python
chlibc /path/to/script.py

Build

Requirements

• Linux x64 or MacOS aarch64
• CMake and Ninja
• pixi (recommended)

Using pixi

./pixiw run configure
./pixiw run build

Using pixi, builds are fully reproducible.

Manual build

cmake --preset clang-x86_64 -S .
./cmake-build --preset clang-x86_64-release