From 7bbb787e87fb224d89412599d2fdadf688ea3bee Mon Sep 17 00:00:00 2001
From: Tom Stellard <tstellar@redhat.com>
Date: Feb 24 2020 17:00:43 +0000
Subject: Manage /usr/bin/cc with update-alternatives


https://fedoraproject.org/wiki/Changes/Use-Update-Alternatives-For-usr-bin-cc

---

diff --git a/gcc.spec b/gcc.spec
index f39c7d1..473575d 100644
--- a/gcc.spec
+++ b/gcc.spec
@@ -4,7 +4,7 @@
 %global gcc_major 10
 # Note, gcc_release must be integer, if you want to add suffixes to
 # %%{release}, append them after %%{gcc_release} on Release: line.
-%global gcc_release 0.8
+%global gcc_release 0.9
 %global nvptx_tools_gitrev 5f6f343a302d620b0868edab376c00b15741e39e
 %global newlib_cygwin_gitrev 50e2a63b04bdd018484605fbb954fd1bd5147fa0
 %global _unpackaged_files_terminate_build 0
@@ -244,6 +244,8 @@ Requires: glibc >= 2.16
 %endif
 Requires: libgcc >= %{version}-%{release}
 Requires: libgomp = %{version}-%{release}
+Requires(post): %{_sbindir}/alternatives
+Requires(preun): %{_sbindir}/alternatives
 %if !%{build_ada}
 Obsoletes: gcc-gnat < %{version}-%{release}
 %endif
@@ -338,6 +340,8 @@ Requires: libstdc++-devel = %{version}-%{release}
 Provides: gcc-g++ = %{version}-%{release}
 Provides: g++ = %{version}-%{release}
 Autoreq: true
+Requires(post): %{_sbindir}/alternatives
+Requires(preun): %{_sbindir}/alternatives
 
 %description c++
 This package adds C++ support to the GNU Compiler Collection.
@@ -1906,6 +1910,12 @@ rm -f %{buildroot}%{mandir}/man3/ffi*
 # Help plugins find out nvra.
 echo gcc-%{version}-%{release}.%{_arch} > $FULLPATH/rpmver
 
+for f in cc c++; do
+  rm %{buildroot}%{_bindir}/$f
+  touch %{buildroot}%{_bindir}/$f
+done
+
+
 %check
 cd obj-%{gcc_target_platform}
 
@@ -1927,6 +1937,12 @@ tar cf - testlogs-%{_target_platform}-%{version}-%{release} | xz -9e \
   | uuencode testlogs-%{_target_platform}.tar.xz || :
 rm -rf testlogs-%{_target_platform}-%{version}-%{release}
 
+%post
+%{_sbindir}/update-alternatives --install %{_bindir}/cc cc %{_bindir}/gcc 50
+
+%post c++
+%{_sbindir}/update-alternatives --install %{_bindir}/c++ c++ %{_bindir}/g++ 50
+
 %post go
 %{_sbindir}/update-alternatives --install \
   %{_prefix}/bin/go go %{_prefix}/bin/go.gcc 92 \
@@ -1950,6 +1966,16 @@ if posix.access ("/sbin/ldconfig", "x") then
   end
 end
 
+%postun
+if [ $1 -eq 0 ] ; then
+  %{_sbindir}/update-alternatives --remove cc %{_bindir}/gcc
+fi
+
+%postun c++
+if [ $1 -eq 0 ] ; then
+  %{_sbindir}/update-alternatives --remove c++ %{_bindir}/g++
+fi
+
 %postun -n libgcc -p <lua>
 if posix.access ("/sbin/ldconfig", "x") then
   local pid = posix.fork ()
@@ -1993,7 +2019,7 @@ end
 %ldconfig_scriptlets -n libgo
 
 %files -f %{name}.lang
-%{_prefix}/bin/cc
+%ghost %{_prefix}/bin/cc
 %{_prefix}/bin/c89
 %{_prefix}/bin/c99
 %{_prefix}/bin/gcc
@@ -2331,7 +2357,7 @@ end
 %files c++
 %{_prefix}/bin/%{gcc_target_platform}-*++
 %{_prefix}/bin/g++
-%{_prefix}/bin/c++
+%ghost %{_prefix}/bin/c++
 %{_mandir}/man1/g++.1*
 %dir %{_prefix}/lib/gcc
 %dir %{_prefix}/lib/gcc/%{gcc_target_platform}
@@ -3003,6 +3029,10 @@ end
 %endif
 
 %changelog
+* Mon Feb 24 2020 Tom Stellard <tstellar@redhat.com> 10.0.1-0.9
+- Manage /usr/bin/cc with update-alternatives
+- https://fedoraproject.org/wiki/Changes/Use-Update-Alternatives-For-usr-bin-cc
+
 * Sun Feb 16 2020 Jakub Jelinek <jakub@redhat.com> 10.0.1-0.8
 - update from trunk
   - PRs analyzer/93212, analyzer/93288, analyzer/93350, analyzer/93356,
diff --git a/tests/cc-alternative/hello.c b/tests/cc-alternative/hello.c
new file mode 100644
index 0000000..237a2b2
--- /dev/null
+++ b/tests/cc-alternative/hello.c
@@ -0,0 +1,5 @@
+#include <stdio.h>
+
+int main() {
+  printf("Hello world\n");
+}
diff --git a/tests/cc-alternative/hello.cpp b/tests/cc-alternative/hello.cpp
new file mode 100644
index 0000000..c3d3882
--- /dev/null
+++ b/tests/cc-alternative/hello.cpp
@@ -0,0 +1,5 @@
+#include <iostream>
+
+int main() {
+  std::cout << "Hello world\n";
+}
diff --git a/tests/cc-alternative/runtest.sh b/tests/cc-alternative/runtest.sh
new file mode 100644
index 0000000..efc5474
--- /dev/null
+++ b/tests/cc-alternative/runtest.sh
@@ -0,0 +1,36 @@
+#!/bin/bash
+
+# This test assumes gcc and gcc-c++ are already installed.
+
+set -exo pipefail
+
+# Verify that /usr/bin/cc points to gcc.
+ls -l /etc/alternatives/cc | grep gcc
+
+# Verify that /usr/bin/c++ points to g++
+ls -l /etc/alternatives/c++ | grep g++
+
+# Run cc and verify it invokes gcc
+/usr/bin/cc --version | grep 'cc (GCC)'
+
+# Run c++ and verify it invokes g++
+/usr/bin/c++ --version | grep 'c++ (GCC)'
+
+# Compile a C program
+/usr/bin/cc -o hello-c hello.c
+./hello-c | grep 'Hello world'
+
+# Compile a C++ program
+/usr/bin/c++ -o hello-cpp hello.cpp
+./hello-cpp | grep 'Hello world'
+
+# Uninstall gcc and verify that cc and c++ are gone.
+dnf remove -y gcc gcc-c++
+
+test ! -h /etc/alternatives/cc
+
+test ! -h /etc/alternatives/c++
+
+test ! -e /usr/bin/cc
+
+test ! -e /usr/bin/c++
diff --git a/tests/tests-cc-alternative.yml b/tests/tests-cc-alternative.yml
new file mode 100644
index 0000000..b104e89
--- /dev/null
+++ b/tests/tests-cc-alternative.yml
@@ -0,0 +1,14 @@
+# The cc-alternative test uninstalls gcc, so it needs to be run by
+# itself in a separate .yml file so it doesn't modify the test
+# environment for other tests.
+
+- hosts: localhost
+  roles:
+  - role: standard-test-basic
+    tags:
+      - classic
+    required_packages:
+      - gcc
+      - gcc-c++
+    tests:
+      - cc-alternative