Windows
On windows, GRE registration information is kept in the win32 registry under the HKEY_LOCAL_MACHINE/Software/mozilla.org/GRE and HKEY_CURRENT_USER/Software/mozilla.org/GRE keys. Each subkey is searched for GRE registration information:
HKLM/Software/mozilla.org/GRE/1.8_1 Version=1.8 GreHome=C:\path\to\installed-dir Feature=Value Feature2=Value2HKLM/Software/mozilla.org/GRE/1.8_2 Version=1.8 GreHome=C:\path\to\second-installation
When installing a GRE via the Mozilla suite GRE installer, the installer will blindly overwrite any previous GRE information in HKLM/Software/mozilla.org/GRE/
When installing a GRE via the command line xulrunner.exe -register-global, XULRunner will detect that there is already an installation at HKLM/Software/mozilla.org/GRE/
Mac
On mac, the only GRE is the libxul framework XUL.framework. This framework is installed either in /Library/Frameworks/XUL.framework/Versions/
Linux
On linux, registration information is kept in INI-style files of the following form:
[1.7.10]GRE_PATH=/usr/lib/mozilla-1.7.10Feature=ValueFeature2=Value2
These INI files can be in any of the following locations:
/etc/gre.conf /etc/gre.d/*.conf ~/.gre.conf ~/.gre.d/*.conf
Mozilla has never officially shipped a linux GRE based on the Mozilla suite. However, some linux distributors including Red Hat/Fedora Core ship /etc/gre.d/*.conf files with the Mozilla suite RPMs.
XULRunner RPMs/post-install scripts should register XULRunner as a GRE by running xulrunner -register-global and not hand-create a .conf file. The -register-global flag has special fallback semantics so that multiple XULRunners of the same version can be installed without overwriting registration files.