G

gcompat

The GNU C Library Compatibility Layer for Adélie Linux

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gcompat

The gcompat project provides a glibc-compatible runtime environment for distributions that use musl libc.

It provides a compatibility library as well as a loader which injects the compatibility library. The loader is installed where the glibc ELF interpreter (/lib/ld-linux.so.2) would normally be, allowing for execution of glibc programs to work in the same way as native musl programs.

building gcompat

In order to build correctly, the gcompat build system requires a few details about the host environment, both from the musl end, as well as the glibc end. These are:

Variable Description
LINKER_PATH The location of the musl ELF interpreter.
LOADER_NAME The name of the glibc ELF interpreter that would be appropriate for your architecture.
LIBGCOMPAT_PATH optional The location to install the libgcompat.so library to. Usually /lib/libgcompat.so.0.
LOADER_PATH optional The location to install the loader to. Usually /lib/${LOADER_NAME}.

For example on x86_64 musl with x86_64 glibc compatibility, you would want to do:

$ make LINKER_PATH=/lib/ld-musl-x86_64.so.1 LOADER_NAME=ld-linux-x86-64.so.2
$ make LINKER_PATH=/lib/ld-musl-x86_64.so.1 LOADER_NAME=ld-linux-x86-64.so.2 install

The DESTDIR environment variable is available for the convenience of packagers.

running programs under gcompat

Assuming everything is in the right place, the programs should just work. If they are not working, check the program's ELF interpreter entry, using scanelf(8) like so:

$ scanelf -i ~/glibcfile
 TYPE   INTERP FILE
ET_EXEC /lib64/ld-linux-x86-64.so.2 /home/kaniini/glibcfile

If the interpreter path is different than expected, use PatchELF or install a symlink to the interpreter.

making musl programs accept glibc binaries for dlopen(3)

Just add libgcompat.so to the DT_NEEDED entries in the ELF that you want to have the gcompat symbols available in. Use a tool such as PatchELF for this.

special environment variables

  • GLIBC_FAKE_VERSION will override the result of gnu_get_libc_version, which currently defaults to "2.8".
  • GLIBC_FAKE_DEBUG will cause dlmopen and dlvsym to display the overrides they are performing, and may cause additional output to stderr with other functions in the future.