How to do an out-of-tree build for AFL++?

[Evian-Zhang]

Currently, the procedures described in docs/INSTALL.md are doing an in-source build, which means all object files and executables generated are also in the source code directory of AFL++. This makes writing fuzzers for multiple platforms (Linux & other UNIX systems, or Linux with different glibc versions) difficult, since the generated file may overwrite the previously generated file for other platforms.

An out-of-tree build, which means the object files and executables can be generated at user-specific directories, is more graceful and clear, and I wonder if afl++ supports out-of-tree build.

As a reference, to out-of-tree build QEMU, we can create a build directory and a bin directory anywhere in the filesystem, then:

cd path/to/build
path/to/qemu-source/configure --prefix path/to/bin
make
make install

Then the generated object files are in the build directory and generated executables are in the bin directory.