How to Cross-Compile UnRAR for Another Architecture

Cross-compiling unrar allows you to generate a lightweight, standalone extraction binary for target architectures like ARM, MIPS, or RISC-V using a more powerful host machine. This guide walks through obtaining the official source code, preparing your cross-toolchain, overriding the build configuration, and verifying the final binary.

Prerequisites

Before beginning, ensure your host system has the standard build utilities and the cross-compiler toolchain for your target architecture installed. For example, to target 64-bit ARM (aarch64):

sudo apt update
sudo apt install build-essential gcc-aarch64-linux-gnu g++-aarch64-linux-gnu

Adjust the package name depending on your target platform (e.g., arm-linux-gnueabihf- for 32-bit ARM or mips-linux-gnu- for MIPS).

Step 1: Download the UnRAR Source Code

Download the portable source code archive directly from RARLAB and extract it:

wget https://www.rarlab.com/rar/unrarsrc-6.2.12.tar.gz
tar -xzf unrarsrc-6.2.12.tar.gz
cd unrar

(Note: Replace the version number with the current release as needed.)

Step 2: Understand the Makefile Structure

UnRAR does not use an autotools configure script or CMake. Instead, it relies on a standard makefile located in the root directory.

Key variables within this makefile include:

CXX: The C++ compiler executable.
STRIP: The strip utility used to reduce binary size.
AR: The archive tool (used if building libunrar).
CXXFLAGS: Compiler flags.
LDFLAGS: Linker flags.

Step 3: Execute the Cross-Compilation

To cross-compile, pass your cross-compiler toolchain prefixes directly to the make command without altering the source files.

Dynamic Binary

For standard cross-compilation linking against the target system's dynamic C runtime:

make -f makefile \
    CXX=aarch64-linux-gnu-g++ \
    STRIP=aarch64-linux-gnu-strip \
    AR=aarch64-linux-gnu-ar

Statically Linked Binary (Recommended for Embedded Systems)

If the target system may lack compatible shared C++ standard libraries, build a statically linked binary:

make -f makefile \
    CXX=aarch64-linux-gnu-g++ \
    STRIP=aarch64-linux-gnu-strip \
    AR=aarch64-linux-gnu-ar \
    LDFLAGS="-static"

Step 4: Verify the Compiled Binary

After the build completes, confirm that the generated executable matches your target architecture rather than your host architecture:

file unrar

Expected output for an aarch64 target:

unrar: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), statically linked, stripped

Step 5: Deploy to Target

Transfer the resulting unrar binary to your target environment using scp, USB, or network storage, and set executable permissions:

chmod +x unrar
./unrar