wrap every unlink call to check for != /dev/null

Unlinking /dev/null is bad, we shouldn't do that. Also, we should print
at least a warning if we tried to unlink a file but didn't manage to
pull it of (ignoring the case were the file is /dev/null or doesn't
exist in the first place).

This got triggered by a relatively unlikely to cause problem in
pkgAcquire::Worker::PrepareFiles which would while temporary
uncompressed files (which are set to keep compressed) figure out that to
files are the same and prepare for sharing by deleting them. Bad move.
That also shows why not printing a warning is a bad idea as this hide
the error for in non-root test runs.

Git-Dch: Ignore

2 files changed, 19 insertions, 4 deletions

diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index 368380af7..e52c8f219 100644
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -172,6 +172,21 @@ bool CopyFile(FileFd &From,FileFd &To)
    return true;
 }
 									/*}}}*/
+bool RemoveFile(char const * const Function, std::string const &FileName)/*{{{*/
+{
+   if (FileName == "/dev/null")
+      return true;
+   errno = 0;
+   if (unlink(FileName.c_str()) != 0)
+   {
+      if (errno == ENOENT)
+	 return true;
+
+      return _error->WarningE(Function,_("Problem unlinking the file %s"), FileName.c_str());
+   }
+   return true;
+}
+									/*}}}*/
 // GetLock - Gets a lock file						/*{{{*/
 // ---------------------------------------------------------------------
 /* This will create an empty file of the given name and lock it. Once this
@@ -1135,13 +1150,13 @@ bool FileFd::Open(string FileName,unsigned int const Mode,APT::Configuration::Co
    else if ((OpenMode & (Exclusive | Create)) == (Exclusive | Create))
    {
       // for atomic, this will be done by rename in Close()
-      unlink(FileName.c_str());
+      RemoveFile("FileFd::Open", FileName);
    }
    if ((OpenMode & Empty) == Empty)
    {
       struct stat Buf;
       if (lstat(FileName.c_str(),&Buf) == 0 && S_ISLNK(Buf.st_mode))
-	 unlink(FileName.c_str());
+	 RemoveFile("FileFd::Open", FileName);
    }
 
    int fileflags = 0;
@@ -2025,8 +2040,7 @@ bool FileFd::Close()
 
    if ((Flags & Fail) == Fail && (Flags & DelOnFail) == DelOnFail &&
        FileName.empty() == false)
-      if (unlink(FileName.c_str()) != 0)
-	 Res &= _error->WarningE("unlnk",_("Problem unlinking the file %s"), FileName.c_str());
+      Res &= RemoveFile("FileFd::Close", FileName);
 
    if (Res == false)
       Flags |= Fail;
diff --git a/apt-pkg/contrib/fileutl.h b/apt-pkg/contrib/fileutl.h
index cddfe2b45..7176e4dea 100644
--- a/apt-pkg/contrib/fileutl.h
+++ b/apt-pkg/contrib/fileutl.h
@@ -150,6 +150,7 @@ class FileFd
 
 bool RunScripts(const char *Cnf);
 bool CopyFile(FileFd &From,FileFd &To);
+bool RemoveFile(char const * const Function, std::string const &FileName);
 int GetLock(std::string File,bool Errors = true);
 bool FileExists(std::string File);
 bool RealFileExists(std::string File);