replace c-string Mode with c++-string ActiveSubprocess

A long-lasting FIXME in the acquire code points out the problem that we
e.g. for decompressors assign c-string representations of c++-strings to
the Mode variable, which e.g. cppcheck points out as very bad.

In practice, nothing major happens as the c++-strings do not run out of
scope until Mode would do, but that is bad style and fragile, so the
obvious proper fix is to use a c++ string for storage to begin with.

The slight complications stems from the fact that progress reporting
code in frontends potentially uses Mode and compares it with NULL, which
can't be done with std::string, so instead of just changing the type we
introduce a new variable and deprecate the old one.

Git-Dch: Ignore

apt-pkg/acquire-item.cc

@@ -64,6 +64,10 @@ static void printHashSumComparision(std::string const &URI, HashStringList const
 									/*}}}*/
 
 // Acquire::Item::Item - Constructor					/*{{{*/
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
 pkgAcquire::Item::Item(pkgAcquire *Owner, HashStringList const &ExpectedHashes) :
    Owner(Owner), FileSize(0), PartialSize(0), Mode(0), ID(0), Complete(false),
    Local(false), QueueCounter(0), ExpectedAdditionalItems(0),
@@ -72,6 +76,9 @@ pkgAcquire::Item::Item(pkgAcquire *Owner, HashStringList const &ExpectedHashes)
    Owner->Add(this);
    Status = StatIdle;
 }
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic pop
+#endif
 									/*}}}*/
 // Acquire::Item::~Item - Destructor					/*{{{*/
 // ---------------------------------------------------------------------
@@ -774,7 +781,15 @@ void pkgAcqIndexDiffs::Done(string Message,unsigned long long Size, HashStringLi
       Local = true;
       Desc.URI = "rred:" + FinalFile;
       QueueURI(Desc);
+      ActiveSubprocess = "rred";
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
       Mode = "rred";
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic pop
+#endif
       return;
    } 
 
@@ -894,7 +909,15 @@ void pkgAcqIndexMergeDiffs::Done(string Message,unsigned long long Size,HashStri
       Local = true;
       Desc.URI = "rred:" + FinalFile;
       QueueURI(Desc);
+      ActiveSubprocess = "rred";
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
       Mode = "rred";
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic pop
+#endif
       return;
    }
    // success in download/apply all diffs, clean up
@@ -1191,7 +1214,15 @@ void pkgAcqIndex::Done(string Message,unsigned long long Size,HashStringList con
       DestFile += ".decomp";
       Desc.URI = "copy:" + FileName;
       QueueURI(Desc);
+      ActiveSubprocess = "copy";
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
       Mode = "copy";
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic pop
+#endif
       return;
    }
 
@@ -1251,8 +1282,15 @@ void pkgAcqIndex::Done(string Message,unsigned long long Size,HashStringList con
    Desc.URI = decompProg + ":" + FileName;
    QueueURI(Desc);
 
-   // FIXME: this points to a c++ string that goes out of scope
-   Mode = decompProg.c_str();
+   ActiveSubprocess = decompProg;
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
+      Mode = ActiveSubprocess.c_str();
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic pop
+#endif
 }
 									/*}}}*/
 // AcqIndexTrans::pkgAcqIndexTrans - Constructor			/*{{{*/
@@ -1554,7 +1592,15 @@ void pkgAcqMetaIndex::Done(string Message,unsigned long long Size,HashStringList
          AuthPass = true;
          Desc.URI = "gpgv:" + SigFile;
          QueueURI(Desc);
-         Mode = "gpgv";
+	 ActiveSubprocess = "gpgv";
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+#endif
+	 Mode = "gpgv";
+#if __GNUC__ >= 4
+	#pragma GCC diagnostic pop
+#endif
 	 return;
       }
    }

apt-pkg/acquire-item.h

@@ -133,7 +133,12 @@ class pkgAcquire::Item : public WeakPointable
    /** \brief If not \b NULL, contains the name of a subprocess that
     *  is operating on this object (for instance, "gzip" or "gpgv").
     */
-   const char *Mode;
+   APT_DEPRECATED const char *Mode;
+
+   /** \brief contains the name of the subprocess that is operating on this object
+    * (for instance, "gzip", "rred" or "gpgv"). This is obsoleting #Mode from above
+    * as it can manage the lifetime of included string properly. */
+   std::string ActiveSubprocess;
 
    /** \brief A client-supplied unique identifier.
     * 

apt-private/acqprogress.cc

@@ -202,9 +202,9 @@ bool AcqTextStatus::Pulse(pkgAcquire *Owner)
       S += strlen(S);
 
       // Show the short mode string
-      if (I->CurrentItem->Owner->Mode != 0)
+      if (I->CurrentItem->Owner->ActiveSubprocess.empty() == false)
       {
-	 snprintf(S,End-S," %s",I->CurrentItem->Owner->Mode);
+	 snprintf(S,End-S, " %s", I->CurrentItem->Owner->ActiveSubprocess.c_str());
 	 S += strlen(S);
       }