apt-pkg/deb/debsystem.cc: Fall back to "dpkg" when Dir::Bin::dpkg is not found

The custom dpkg binary may be removed by apt and that breaks the end of
the operation. This can be observed when using eatmydata as dpkg and
removing the symlink to eatmydata when removing the apt-eatmydata package.

1 files changed, 10 insertions, 1 deletions

diff --git a/apt-pkg/deb/debsystem.cc b/apt-pkg/deb/debsystem.cc
index 8533b1157..749969759 100644
--- a/apt-pkg/deb/debsystem.cc
+++ b/apt-pkg/deb/debsystem.cc
@@ -392,7 +392,16 @@ std::string debSystem::StripDpkgChrootDirectory(std::string const &File)/*{{{*/
 									/*}}}*/
 std::string debSystem::GetDpkgExecutable()				/*{{{*/
 {
-   return StripDpkgChrootDirectory(_config->Find("Dir::Bin::dpkg","dpkg"));
+   std::string dpkg_executable = _config->Find("Dir::Bin::dpkg","dpkg");
+   if (APT::String::Startswith(dpkg_executable, "/")) {
+      struct stat buf;
+      if (stat(dpkg_executable.c_str(), &buf) != 0) {
+         _error->Warning(_("The dpkg executable set in Dir::Bin::dpkg is "
+                          "missing, falling back to using default dpkg."));
+        dpkg_executable = "dpkg";
+      }
+   }
+   return StripDpkgChrootDirectory(dpkg_executable);
 }
 									/*}}}*/
 std::vector<std::string> debSystem::GetDpkgBaseCommand()		/*{{{*/