avoid some useless casts reported by -Wuseless-cast

The casts are useless, but the reports show some where we can actually
improve the code by replacing them with better alternatives like
converting whatever int type into a string instead of casting to a
specific one which might in the future be too small.

Reported-By: gcc -Wuseless-cast

apt-pkg/cdrom.cc

@@ -315,7 +315,7 @@ bool pkgCdrom::DropRepeats(vector<string> &List,const char *Name)
       for (std::vector<APT::Configuration::Compressor>::const_iterator c = compressor.begin();
 	   c != compressor.end(); ++c)
       {
-	 std::string filename = std::string(List[I]).append(Name).append(c->Extension);
+	 std::string const filename = List[I] + Name + c->Extension;
          if (stat(filename.c_str(), &Buf) != 0)
 	    continue;
 	 Inodes[I] = Buf.st_ino;

apt-pkg/contrib/cdromutl.cc

@@ -105,13 +105,14 @@ bool UnmountCdrom(string Path)
 	 }
 	 else
 	 {
-	    const char *Args[10];
-	    Args[0] = "umount";
-	    Args[1] = Path.c_str();
-	    Args[2] = 0;
-	    execvp(Args[0],(char **)Args);      
+	    const char * const Args[] = {
+	       "umount",
+	       Path.c_str(),
+	       nullptr
+	    };
+	    execvp(Args[0], const_cast<char **>(Args));
 	    _exit(100);
-	 }      
+	 }
       }
 
       // if it can not be umounted, give it a bit more time
@@ -222,15 +223,13 @@ bool IdentCdrom(string CD,string &Res,unsigned int Version)
 
       std::string S;
       if (Version <= 1)
-      {
-	 strprintf(S, "%lu", (unsigned long)Dir->d_ino);
-      }
+	 S = std::to_string(Dir->d_ino);
       else
       {
 	 struct stat Buf;
 	 if (fstatat(dirfd, Dir->d_name, &Buf, 0) != 0)
 	    continue;
-	 strprintf(S, "%lu", (unsigned long)Buf.st_mtime);
+	 S = std::to_string(Buf.st_mtime);
       }
 
       Hash.Add(S.c_str());
@@ -246,21 +245,17 @@ bool IdentCdrom(string CD,string &Res,unsigned int Version)
 	 return _error->Errno("statfs",_("Failed to stat the cdrom"));
 
       // We use a kilobyte block size to avoid overflow
-      if (writable_media)
-      {
-         strprintf(S, "%lu", (unsigned long)(Buf.f_blocks*(Buf.f_bsize/1024)));
-      } else {
-         strprintf(S, "%lu %lu", (unsigned long)(Buf.f_blocks*(Buf.f_bsize/1024)),
-                 (unsigned long)(Buf.f_bfree*(Buf.f_bsize/1024)));
-      }
-      Hash.Add(S.c_str());
+      S = std::to_string(Buf.f_blocks * (Buf.f_bsize / 1024));
+      if (writable_media == false)
+	 S.append(" ").append(std::to_string(Buf.f_bfree * (Buf.f_bsize / 1024)));
+      Hash.Add(S.c_str(), S.length());
       strprintf(S, "-%u", Version);
    }
    else
       strprintf(S, "-%u.debug", Version);
 
    closedir(D);
-   Res = Hash.Result().Value() + S;
+   Res = Hash.Result().Value().append(std::move(S));
    return true;
 }
 									/*}}}*/

apt-pkg/indexcopy.cc

@@ -58,15 +58,14 @@ bool IndexCopy::CopyPackages(string CDROM,string Name,vector<string> &List,
    // Prepare the progress indicator
    off_t TotalSize = 0;
    std::vector<APT::Configuration::Compressor> const compressor = APT::Configuration::getCompressors();
-   for (vector<string>::iterator I = List.begin(); I != List.end(); ++I)
+   for (auto const &F : List)
    {
       struct stat Buf;
       bool found = false;
-      std::string file = std::string(*I).append(GetFileName());
-      for (std::vector<APT::Configuration::Compressor>::const_iterator c = compressor.begin();
-	   c != compressor.end(); ++c)
+      auto const file = F + GetFileName();
+      for (auto const &ext: APT::Configuration::getCompressorExtensions())
       {
-	 if (stat((file + c->Extension).c_str(), &Buf) != 0)
+	 if (stat((file + ext).c_str(), &Buf) != 0)
 	    continue;
 	 found = true;
 	 break;
@@ -82,9 +81,9 @@ bool IndexCopy::CopyPackages(string CDROM,string Name,vector<string> &List,
    unsigned int WrongSize = 0;
    unsigned int Packages = 0;
    for (vector<string>::iterator I = List.begin(); I != List.end(); ++I)
-   {      
-      string OrigPath = string(*I,CDROM.length());
-      
+   {
+      std::string OrigPath(*I,CDROM.length());
+
       // Open the package file
       FileFd Pkg(*I + GetFileName(), FileFd::ReadOnly, FileFd::Auto);
       off_t const FileSize = Pkg.Size();

apt-private/private-source.cc

@@ -208,12 +208,7 @@ static pkgSrcRecords::Parser *FindSrc(const char *Name,
 	 // or RelTag
 	 if (Cache.BuildPolicy() == false)
 	    return nullptr;
-	 pkgPolicy * Policy = dynamic_cast<pkgPolicy*>(Cache.GetPolicy());
-	 if (Policy == nullptr)
-	 {
-	    _error->Fatal("Implementation error: dynamic up-casting policy engine failed in FindSrc!");
-	    return nullptr;
-	 }
+	 pkgPolicy * const Policy = Cache.GetPolicy();
 	 pkgCache::VerIterator const Ver = Policy->GetCandidateVer(Pkg);
 	 if (Ver.end() == false)
 	 {

cmdline/apt-config.cc

@@ -128,7 +128,7 @@ int main(int argc,const char *argv[])					/*{{{*/
       _config->Set(comp + "Name", c->Name);
       _config->Set(comp + "Extension", c->Extension);
       _config->Set(comp + "Binary", c->Binary);
-      _config->Set(std::string(comp + "Cost").c_str(), c->Cost);
+      _config->Set((comp + "Cost").c_str(), c->Cost);
       for (std::vector<std::string>::const_iterator a = c->CompressArgs.begin(); a != c->CompressArgs.end(); ++a)
 	 _config->Set(comp + "CompressArg::", *a);
       for (std::vector<std::string>::const_iterator a = c->UncompressArgs.begin(); a != c->UncompressArgs.end(); ++a)

ftparchive/writer.cc

@@ -477,10 +477,7 @@ bool PackagesWriter::DoPackage(string FileName)
 
    // This lists all the changes to the fields we are going to make.
    std::vector<pkgTagSection::Tag> Changes;
-
-   std::string Size;
-   strprintf(Size, "%llu", (unsigned long long) FileSize);
-   Changes.push_back(pkgTagSection::Tag::Rewrite("Size", Size));
+   Changes.push_back(pkgTagSection::Tag::Rewrite("Size", std::to_string(FileSize)));
 
    for (HashStringList::const_iterator hs = Db.HashesList.begin(); hs != Db.HashesList.end(); ++hs)
    {

methods/basehttp.cc

@@ -191,7 +191,7 @@ bool RequestState::HeaderLine(string const &Line)			/*{{{*/
 	 ; // we got the expected filesize which is all we wanted
       else if (sscanf(Val.c_str(),"bytes %llu-%*u/%llu",&StartPos,&TotalFileSize) != 2)
 	 return _error->Error(_("The HTTP server sent an invalid Content-Range header"));
-      if ((unsigned long long)StartPos > TotalFileSize)
+      if (StartPos > TotalFileSize)
 	 return _error->Error(_("This HTTP server has broken range support"));
 
       // figure out what we will download

test/libapt/getlistoffilesindir_test.cc

@@ -11,7 +11,7 @@
 
 #include "file-helpers.h"
 
-#define P(x)	std::string(tempdir).append("/").append(x)
+#define P(x)	tempdir + "/" + x
 
 TEST(FileUtlTest,GetListOfFilesInDir)
 {

test/libapt/globalerror_test.cc

@@ -111,11 +111,11 @@ TEST(GlobalErrorTest,LongMessage)
       longText.append("a");
    EXPECT_FALSE(e.Error("%s horrible %s %d times", longText.c_str(), "happened", 2));
    EXPECT_TRUE(e.PopMessage(text));
-   EXPECT_EQ(std::string(longText).append(" horrible happened 2 times"), text);
+   EXPECT_EQ(longText + " horrible happened 2 times", text);
 
    EXPECT_FALSE(e.Errno("errno", "%s horrible %s %d times", longText.c_str(), "happened", 2));
    EXPECT_TRUE(e.PopMessage(text));
-   EXPECT_EQ(std::string(longText).append(" horrible happened 2 times - errno (0: ").append(textOfErrnoZero).append(")"), text);
+   EXPECT_EQ(longText + " horrible happened 2 times - errno (0: " + textOfErrnoZero + ")", text);
 
    EXPECT_FALSE(e.Error("%s horrible %s %d times", longText.c_str(), "happened", 2));
    std::ostringstream out;