Ignore SIGINT and SIGQUIT for Pre-Install hooks

Instead of erroring out when receiving a SIGINT, let the
child deal with it - we'll error out anyway if the child
exits with an error or due to the signal. Also ignore
SIGQUIT, as system() ignores it.

This basically fixes Bug #832593, but: we are running
the hooks via sh -c. Some shells exit with a signal
error even if the command they are executing catches
the signal and exits successfully. So far, this has
been noticed on dash, which unfortunately, is our
default shell.

Example:
$ cat trap.sh
trap 'echo int' INT; sleep 10; exit 0
$ if dash -c ./trap.sh; then echo OK: $?; else echo FAIL: $?; fi
^Cint
FAIL: 130
$ if mksh -c ./trap.sh; then echo OK: $?; else echo FAIL: $?; fi
^Cint
OK: 0
$ if bash -c ./trap.sh; then echo OK: $?; else echo FAIL: $?; fi
^Cint
OK: 0

(cherry picked from commit a6ae3d3df490e7a5a1c8324ba9dc2e63972b1529)

1 files changed, 5 insertions, 1 deletions

diff --git a/apt-pkg/deb/dpkgpm.cc b/apt-pkg/deb/dpkgpm.cc
index d224a34c0..533d9b367 100644
--- a/apt-pkg/deb/dpkgpm.cc
+++ b/apt-pkg/deb/dpkgpm.cc
@@ -414,7 +414,9 @@ bool pkgDPkgPM::RunScriptsWithPkgs(const char *Cnf)
    Opts = Opts->Child;
 
    sighandler_t old_sigpipe = signal(SIGPIPE, SIG_IGN);
-   
+   sighandler_t old_sigint = signal(SIGINT, SIG_IGN);
+   sighandler_t old_sigquit = signal(SIGQUIT, SIG_IGN);
+
    unsigned int Count = 1;
    for (; Opts != 0; Opts = Opts->Next, Count++)
    {
@@ -512,7 +514,9 @@ bool pkgDPkgPM::RunScriptsWithPkgs(const char *Cnf)
          break;
       }
    }
+   signal(SIGINT, old_sigint);
    signal(SIGPIPE, old_sigpipe);
+   signal(SIGQUIT, old_sigquit);
 
    return result;
 }