fix tight loop detection and temporary removes

As outlined in #748355 apt segfaulted if it encountered a loop between a
package pre-depending on a package conflicting with the previous as it
ended up in an endless loop trying to unpack 'the other package'.

In this specific case as an essential package is involved a lot of force
needs to be applied, but can also be caused by 'normal' tight loops and
highlights a problem in how we handle breaks which we want to avoid.

The fix comes in multiple entangled changes:
1. All Smart* calls are guarded with loop detection. Some already had it,
   some had parts of it, some did it incorrect, and some didn't even try.
2. temporary removes to avoid a loop (which is done if a loop is
   detected) prevent the unpack of this looping package (we tried to unpack
   it to avoid the conflict/breaks, but due to a loop we couldn't, so we
   remove/deconfigure it instead which means we can't unpack it now)
3. handle conflicts and breaks very similar instead of duplicating most
   of the code. The only remaining difference is, as it should:
   deconfigure is enough for breaks, for conflicts we need the big hammer

4 files changed, 86 insertions, 18 deletions

diff --git a/test/integration/test-bug-618288-multiarch-same-lockstep b/test/integration/test-bug-618288-multiarch-same-lockstep
index e0305b64b..536124c2c 100755
--- a/test/integration/test-bug-618288-multiarch-same-lockstep
+++ b/test/integration/test-bug-618288-multiarch-same-lockstep
@@ -16,22 +16,23 @@ buildsimplenativepackage 'apt' 'i386' '2' 'unstable' 'Depends: libsame (= 2)' ''
 buildsimplenativepackage 'apt2' 'amd64' '2' 'unstable' 'Depends: libsame (= 2)' '' 'required'
 
 setupaptarchive
-aptget dist-upgrade -s >output.apt 2>&1
+testsuccess aptget dist-upgrade -s -o Debug::pkgPackageManager=1
 
 # order in switch libsame:{amd64,i386} are unpacked is irrelevant, as both are installed - but we need to do it together
-LS_U_AMD="$(grep -o -n '^Inst libsame ' output.apt | cut -d: -f1)"
-LS_U_INT="$(grep -o -n '^Inst libsame:i386 ' output.apt | cut -d: -f1)"
-LS_C_AMD="$(grep -o -n '^Conf libsame ' output.apt | cut -d: -f1)"
-LS_C_INT="$(grep -o -n '^Conf libsame:i386 ' output.apt | cut -d: -f1)"
+OUTPUT=rootdir/tmp/testsuccess.output
+LS_U_AMD="$(grep -o -n '^Inst libsame ' $OUTPUT | cut -d: -f1)"
+LS_U_INT="$(grep -o -n '^Inst libsame:i386 ' $OUTPUT | cut -d: -f1)"
+LS_C_AMD="$(grep -o -n '^Conf libsame ' $OUTPUT | cut -d: -f1)"
+LS_C_INT="$(grep -o -n '^Conf libsame:i386 ' $OUTPUT | cut -d: -f1)"
 
-msgtest 'Test if libsame:amd64 unpack before configure'
+msgtest 'Test if' 'libsame:amd64 unpack before configure'
 test "$LS_U_AMD" -lt "$LS_C_AMD" && msgpass || msgfail
 
-msgtest 'Test if libsame:i386 unpack before configure'
+msgtest 'Test if' 'libsame:i386 unpack before configure'
 test "$LS_U_INT" -lt "$LS_C_INT" && msgpass || msgfail
 
-msgtest 'Test if libsame:amd64 unpack is before libsame:i386 configure'
+msgtest 'Test if' 'libsame:amd64 unpack is before libsame:i386 configure'
 test "$LS_U_AMD" -lt "$LS_C_INT" && msgpass || msgfail
 
-msgtest 'Test if libsame:i386 unpack is before libsame:amd64 configure'
+msgtest 'Test if' 'libsame:i386 unpack is before libsame:amd64 configure'
 test "$LS_U_INT" -lt "$LS_C_AMD" && msgpass || msgfail
diff --git a/test/integration/test-bug-673536-pre-depends-breaks-loop b/test/integration/test-bug-673536-pre-depends-breaks-loop
index f6a90b21f..21bd5e065 100755
--- a/test/integration/test-bug-673536-pre-depends-breaks-loop
+++ b/test/integration/test-bug-673536-pre-depends-breaks-loop
@@ -6,18 +6,32 @@ TESTDIR=$(readlink -f $(dirname $0))
 setupenvironment
 configarchitecture 'native'
 
-buildsimplenativepackage 'basic' 'native' '1' 'stable'
+buildsimplenativepackage 'advanced' 'native' '1' 'stable'
+buildsimplenativepackage 'advanced' 'native' '2' 'unstable' 'Pre-Depends: basic'
 buildsimplenativepackage 'basic' 'native' '2' 'unstable' 'Pre-Depends: common'
-buildsimplenativepackage 'common' 'native' '2' 'unstable' 'Breaks: basic (<= 1)'
+
+buildsimplenativepackage 'common' 'native' '2~conflict' 'unstable-conflict' 'Conflicts: advanced (<= 1)'
+buildsimplenativepackage 'common' 'native' '2~break' 'unstable-break' 'Conflicts: advanced (<= 1)'
 
 setupaptarchive
 
 # we check with 'real' packages here as the simulation reports a 'Conf broken'
 # which is technical correct for the simulation, but testing errormsg is ugly
 
-testsuccess aptget install basic=1 -y
-testdpkginstalled basic
-testdpkgnotinstalled common
+cp -a rootdir/var/lib/dpkg/status dpkg.status.backup
+
+testloopbreak() {
+	cp -a dpkg.status.backup rootdir/var/lib/dpkg/status
+	rm -f rootdir/var/lib/apt/extended_states
+
+
+	testsuccess aptget install advanced=1 -y -t "$1" -o Debug::pkgPackageManager=1
+	testdpkginstalled advanced
+	testdpkgnotinstalled basic common
+
+	testsuccess aptget dist-upgrade -y -t "$1" -o Debug::pkgPackageManager=1
+	testdpkginstalled advanced basic common
+}
 
-testsuccess aptget dist-upgrade -y
-testdpkginstalled basic common
+testloopbreak 'unstable-break'
+testloopbreak 'unstable-conflict'
diff --git a/test/integration/test-conflicts-loop b/test/integration/test-conflicts-loop
index 4978fe1e8..a2c411aaf 100755
--- a/test/integration/test-conflicts-loop
+++ b/test/integration/test-conflicts-loop
@@ -20,11 +20,13 @@ Building dependency tree...
 The following packages will be upgraded:
   openjdk-6-jre openjdk-6-jre-headless openjdk-6-jre-lib
 3 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
-Remv openjdk-6-jre [6b16-1.8-0ubuntu1]
+Remv openjdk-6-jre-headless [6b16-1.8-0ubuntu1]
 Remv openjdk-6-jre-lib [6b16-1.8-0ubuntu1]
-Inst openjdk-6-jre-headless [6b16-1.8-0ubuntu1] (6b20-1.9.8-0ubuntu1~10.04.1 unstable [i386])
 Inst openjdk-6-jre [6b16-1.8-0ubuntu1] (6b20-1.9.8-0ubuntu1~10.04.1 unstable [i386])
 Inst openjdk-6-jre-lib [6b16-1.8-0ubuntu1] (6b20-1.9.8-0ubuntu1~10.04.1 unstable [i386])
 Conf openjdk-6-jre-lib (6b20-1.9.8-0ubuntu1~10.04.1 unstable [i386])
 Conf openjdk-6-jre (6b20-1.9.8-0ubuntu1~10.04.1 unstable [i386])
+Inst openjdk-6-jre-headless [6b16-1.8-0ubuntu1] (6b20-1.9.8-0ubuntu1~10.04.1 unstable [i386])
 Conf openjdk-6-jre-headless (6b20-1.9.8-0ubuntu1~10.04.1 unstable [i386])' aptget dist-upgrade -s -o APT::Immediate-Configure-All=true
+
+testsuccess aptget dist-upgrade -s -o Debug::pkgPackageManager=1
diff --git a/test/integration/test-essential-force-loopbreak b/test/integration/test-essential-force-loopbreak
new file mode 100755
index 000000000..842dce61c
--- /dev/null
+++ b/test/integration/test-essential-force-loopbreak
@@ -0,0 +1,51 @@
+#!/bin/sh
+set -e
+
+TESTDIR=$(readlink -f $(dirname $0))
+. $TESTDIR/framework
+
+setupenvironment
+configarchitecture 'amd64'
+
+insertinstalledpackage 'sysvinit' 'amd64' '1' 'Essential: yes'
+
+buildsimplenativepackage 'sysvinit' 'amd64' '2' 'sid' 'Pre-Depends: sysvinit-core | systemd-sysv
+Essential: yes'
+buildsimplenativepackage 'sysvinit-core' 'amd64' '2' 'sid'
+
+buildsimplenativepackage 'systemd-sysv' 'amd64' '2~conflict' 'sid-conflict' 'Conflicts: sysvinit (<< 2)
+Breaks: sysvinit-core'
+
+buildsimplenativepackage 'systemd-sysv' 'amd64' '2~break' 'sid-break' 'Breaks: sysvinit (<< 2), sysvinit-core'
+
+setupaptarchive
+
+cp -a rootdir/var/lib/dpkg/status dpkg.status.backup
+
+testforcebreak() {
+	cp -a dpkg.status.backup rootdir/var/lib/dpkg/status
+	rm -f rootdir/var/lib/apt/extended_states
+	testequal 'Reading package lists...
+Building dependency tree...
+The following extra packages will be installed:
+  sysvinit
+The following NEW packages will be installed:
+  systemd-sysv
+The following packages will be upgraded:
+  sysvinit
+1 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
+E: This installation run will require temporarily removing the essential package sysvinit:amd64 due to a Conflicts/Pre-Depends loop. This is often bad, but if you really want to do it, activate the APT::Force-LoopBreak option.
+E: Internal Error, Could not early remove sysvinit:amd64 (2)' aptget install systemd-sysv -t "$1" -s
+	# ensure that really nothing happens
+	testfailure aptget install systemd-sysv -y -t "$1" -o Debug::pkgPackageManager=1
+	testdpkginstalled 'sysvinit'
+	testdpkgnotinstalled 'systemd-sysv'
+
+	# with enough force however …
+	cp -a dpkg.status.backup rootdir/var/lib/dpkg/status
+	testsuccess aptget install systemd-sysv -y -t "$1" -o Debug::pkgPackageManager=1 -o APT::Force-LoopBreak=1
+	testdpkginstalled 'sysvinit' 'systemd-sysv'
+}
+
+testforcebreak 'sid-conflict'
+testforcebreak 'sid-break'