Fix triggers for the installation and removal of gcc-plugin-annobin.

Resolves: #2167713

redhat-rpm-config.spec

@@ -6,7 +6,7 @@
 
 Summary: Red Hat specific rpm configuration files
 Name: redhat-rpm-config
-Version: 197
+Version: 198
 Release: 1%{?dist}
 # No version specified.
 License: GPL+
@@ -169,16 +169,49 @@ install -p -m 644 -t %{buildroot}%{_rpmluadir}/fedora/srpm forge.lua
 
 # This trigger is used to decide which version of the annobin plugin for gcc
 # should be used.  See comments in the script for full details.
+#
+# Note: for RHEL the rpm containing the annobin built plugin is called
+# "annobin", whereas in Fedora it is called "annobin-plugin-gcc".  This is
+# for historical reasons and will change with the introduction of RHEL-10.
+#
+# Note - whilst "gcc-plugin-annobin" requires "gcc" and hence in theory we
+# do not need to trigger on "gcc", the redhat-annobin-plugin-select.sh
+# script invokes gcc to determine the version of the gcc plugin, and this
+# can be significant.
+#
+# For example, suppose that version N of gcc is installed and that annobin
+# version A (built by gcc version N) is also installed.  Then a new version
+# of gcc is released.  If the rpms are updated in this order:
+#   gcc-plugin-annobin
+#   gcc
+# then when the trigger for gcc-plugin-annobin is run, the script will see
+# (the not yet updated) gcc is currently version N, which matches the current
+# annobin plugin A, so no changes are necessary.  Then gcc is updated and,
+# if the trigger below did not include "gcc", the script would not run again
+# and so now you would have an out of date version of the annobin plugin.
+#
+# Alternatively imagine installing gcc and annobin for the first time.
+# If the installation order is:
+#    gcc
+#    annobin-plugin-gcc
+#    gcc-plugin-annobin
+# then the installation of gcc will not cause the gcc-plugin-annobin to be
+# selected, since it does not exist yet.  Then annobin-plugin-gcc is installed
+# and since it is the only plugin, it will be selected.  Then
+# gcc-plugin-annobin is installed, and if the trigger below was not set to
+# run on gcc-plugin-annobin, it would pass unnoticed.
+#
+# Hence it is necessary to trigger on both gcc and gcc-plugin-annobin.
 
-%triggerin -- annobin gcc-plugin-annobin
+%triggerin -- annobin gcc-plugin-annobin gcc
 %{rrcdir}/redhat-annobin-plugin-select.sh
 %end
 
-# We also trigger when annobin is uninstalled.  This allows us to switch
-# over to the gcc generated version of the plugin.  It does not matter if
+# We also trigger when an annobin plugin is uninstalled.  This allows us to switch
+# over to the other version of the plugin.  It does not matter if
 # gcc is uninstalled, since if that happens the plugin cannot be used.
 
-%triggerpostun -- annobin
+%triggerpostun -- annobin gcc-plugin-annobin
 %{rrcdir}/redhat-annobin-plugin-select.sh
 %end
 
@@ -216,6 +249,9 @@ install -p -m 644 -t %{buildroot}%{_rpmluadir}/fedora/srpm forge.lua
 %doc buildflags.md
 
 %changelog
+* Tue Feb 07 2023 Nick Clifton  <nickc@redhat.com> - 198-1
+- Fix triggers for the installation and removal of gcc-plugin-annobin.  (#2167713)
+
 * Wed Sep 21 2022 Timm Bäder <tbaeder@redhat.com> - 197-1
 - Ship brp-llvm-compile-lto-elf script