Add 'explicit' to most single argument constructors

This prevents implicit conversions that we do not want, such
as having a FileFd* being converted to a debListParser.

Two cases are not yet handled because they require changes
in code using them:

1. The classes in hashes.h
2. The URI class - this one is used quite a lot

19 files changed, 34 insertions, 32 deletions

diff --git a/apt-inst/contrib/arfile.h b/apt-inst/contrib/arfile.h
index 8124208c9..cf454941e 100644
--- a/apt-inst/contrib/arfile.h
+++ b/apt-inst/contrib/arfile.h
@@ -44,7 +44,7 @@ class ARArchive
    const Member *FindMember(const char *Name) const;
    inline Member *Members() { return List; }
    
-   ARArchive(FileFd &File);
+   explicit ARArchive(FileFd &File);
    ~ARArchive();
 };
 
diff --git a/apt-inst/deb/debfile.h b/apt-inst/deb/debfile.h
index 23a76bfdf..21c59a567 100644
--- a/apt-inst/deb/debfile.h
+++ b/apt-inst/deb/debfile.h
@@ -56,7 +56,7 @@ class debDebFile
    const ARArchive::Member *GotoMember(const char *Name);
    inline FileFd &GetFile() {return File;};
    
-   debDebFile(FileFd &File);
+   explicit debDebFile(FileFd &File);
 };
 
 class debDebFile::ControlExtract : public pkgDirStream
@@ -87,7 +87,7 @@ class debDebFile::MemControlExtract : public pkgDirStream
    bool TakeControl(const void *Data,unsigned long long Size);
 
    MemControlExtract() : IsControl(false), Control(0), Length(0), Member("control") {};
-   MemControlExtract(std::string Member) : IsControl(false), Control(0), Length(0), Member(Member) {};
+   explicit MemControlExtract(std::string Member) : IsControl(false), Control(0), Length(0), Member(Member) {};
    ~MemControlExtract() {delete [] Control;};   
 };
 									/*}}}*/
diff --git a/apt-inst/filelist.h b/apt-inst/filelist.h
index 7fe43de63..c5f103d87 100644
--- a/apt-inst/filelist.h
+++ b/apt-inst/filelist.h
@@ -97,7 +97,7 @@ class pkgFLCache
    bool AddConfFile(const char *Name,const char *NameEnd,
 		    PkgIterator const &Owner,const unsigned char *Sum);
 
-   pkgFLCache(DynamicMMap &Map);
+   explicit pkgFLCache(DynamicMMap &Map);
 //   ~pkgFLCache();
 };
 
@@ -288,7 +288,7 @@ class pkgFLCache::NodeIterator
    Package *RealPackage() const;
 
    NodeIterator() : Nde(0), Type(NdeHash), Owner(0) {};
-   NodeIterator(pkgFLCache &Owner) : Nde(Owner.NodeP), Type(NdeHash), Owner(&Owner) {}
+   explicit NodeIterator(pkgFLCache &Owner) : Nde(Owner.NodeP), Type(NdeHash), Owner(&Owner) {}
    NodeIterator(pkgFLCache &Owner,Node *Trg) : Nde(Trg), Type(NdeHash), Owner(&Owner) {}
    NodeIterator(pkgFLCache &Owner,Node *Trg,Package *) : Nde(Trg), Type(NdePkg), Owner(&Owner) {}
 };
diff --git a/apt-pkg/contrib/configuration.h b/apt-pkg/contrib/configuration.h
index 2a3ae1aa4..b5dfe721f 100644
--- a/apt-pkg/contrib/configuration.h
+++ b/apt-pkg/contrib/configuration.h
@@ -119,7 +119,7 @@ class Configuration
    void Dump(std::ostream& str, char const * const root,
 	     char const * const format, bool const emptyValue);
 
-   Configuration(const Item *Root);
+   explicit Configuration(const Item *Root);
    Configuration();
    ~Configuration();
 
@@ -130,7 +130,7 @@ class Configuration
      APT_HIDDEN void clearPatterns();
 
    public:
-     MatchAgainstConfig(char const * Config);
+     explicit MatchAgainstConfig(char const * Config);
      virtual ~MatchAgainstConfig();
 
      /** \brief Returns \b true for a string matching one of the patterns */
diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index 3b4a4a10c..8d6cb3146 100644
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -1944,7 +1944,7 @@ class APT_HIDDEN LzmaFileFdPrivate: public FileFdPrivate {				/*{{{*/
       bool eof;
       bool compressing;
 
-      LZMAFILE(FileFd * const fd) : file(nullptr), filefd(fd), eof(false), compressing(false) { buffer[0] = '\0'; }
+      explicit LZMAFILE(FileFd * const fd) : file(nullptr), filefd(fd), eof(false), compressing(false) { buffer[0] = '\0'; }
       ~LZMAFILE()
       {
 	 if (compressing == true && filefd->Failed() == false)
diff --git a/apt-pkg/contrib/mmap.h b/apt-pkg/contrib/mmap.h
index 63d54d27c..3af1f47fb 100644
--- a/apt-pkg/contrib/mmap.h
+++ b/apt-pkg/contrib/mmap.h
@@ -74,7 +74,7 @@ class MMap
    bool Sync(unsigned long Start,unsigned long Stop);
    
    MMap(FileFd &F,unsigned long Flags);
-   MMap(unsigned long Flags);
+   explicit MMap(unsigned long Flags);
    virtual ~MMap();
 };
 
diff --git a/apt-pkg/contrib/progress.h b/apt-pkg/contrib/progress.h
index 4406a388b..903e6613e 100644
--- a/apt-pkg/contrib/progress.h
+++ b/apt-pkg/contrib/progress.h
@@ -80,9 +80,9 @@ class OpTextProgress : public OpProgress
 
    virtual void Done() APT_OVERRIDE;
    
-   OpTextProgress(bool NoUpdate = false) : NoUpdate(NoUpdate), 
+   explicit OpTextProgress(bool NoUpdate = false) : NoUpdate(NoUpdate),
                 NoDisplay(false), LastLen(0) {};
-   OpTextProgress(Configuration &Config);
+   explicit OpTextProgress(Configuration &Config);
    virtual ~OpTextProgress() {Done();};
 };
 
diff --git a/apt-pkg/deb/debindexfile.h b/apt-pkg/deb/debindexfile.h
index 5c89f9c54..222fed229 100644
--- a/apt-pkg/deb/debindexfile.h
+++ b/apt-pkg/deb/debindexfile.h
@@ -44,7 +44,7 @@ public:
 
    virtual pkgCacheListParser * CreateListParser(FileFd &Pkg) APT_OVERRIDE;
 
-   debStatusIndex(std::string const &File);
+   explicit debStatusIndex(std::string const &File);
    virtual ~debStatusIndex();
 };
 
@@ -83,7 +83,7 @@ public:
    // Interface for the Cache Generator
    virtual bool HasPackages() const APT_OVERRIDE;
 
-   debTranslationsIndex(IndexTarget const &Target);
+   explicit debTranslationsIndex(IndexTarget const &Target);
    virtual ~debTranslationsIndex();
 };
 
@@ -141,7 +141,7 @@ public:
 
    // Interface for acquire
 
-   debDebPkgFileIndex(std::string const &DebFile);
+   explicit debDebPkgFileIndex(std::string const &DebFile);
    virtual ~debDebPkgFileIndex();
 
    //FIXME: use proper virtual-handling on next ABI break
@@ -162,7 +162,7 @@ public:
    virtual pkgSrcRecords::Parser *CreateSrcParser() const APT_OVERRIDE;
    virtual bool HasPackages() const APT_OVERRIDE {return false;};
 
-   debDscFileIndex(std::string const &DscFile);
+   explicit debDscFileIndex(std::string const &DscFile);
    virtual ~debDscFileIndex();
 };
 
@@ -191,7 +191,7 @@ public:
    // Abort if the file does not exist.
    virtual bool Exists() const APT_OVERRIDE {return true;};
 
-   debStringPackageIndex(std::string const &content);
+   explicit debStringPackageIndex(std::string const &content);
    virtual ~debStringPackageIndex();
 };
 #endif
diff --git a/apt-pkg/deb/deblistparser.h b/apt-pkg/deb/deblistparser.h
index f02252d58..ad2b947fe 100644
--- a/apt-pkg/deb/deblistparser.h
+++ b/apt-pkg/deb/deblistparser.h
@@ -121,7 +121,7 @@ class APT_HIDDEN debListParser : public pkgCacheListParser
 
    APT_PUBLIC static const char *ConvertRelation(const char *I,unsigned int &Op);
 
-   debListParser(FileFd *File);
+   explicit debListParser(FileFd *File);
    virtual ~debListParser();
 };
 
@@ -145,7 +145,7 @@ class APT_HIDDEN debTranslationsParser : public debListParser
    virtual APT::StringView Version() APT_OVERRIDE { return ""; }
 #endif
 
-   debTranslationsParser(FileFd *File)
+   explicit debTranslationsParser(FileFd *File)
       : debListParser(File) {};
 };
 
@@ -153,7 +153,7 @@ class APT_HIDDEN debStatusListParser : public debListParser
 {
  public:
    virtual bool ParseStatus(pkgCache::PkgIterator &Pkg,pkgCache::VerIterator &Ver);
-   debStatusListParser(FileFd *File)
+   explicit debStatusListParser(FileFd *File)
       : debListParser(File) {};
 };
 #endif
diff --git a/apt-pkg/deb/debmetaindex.cc b/apt-pkg/deb/debmetaindex.cc
index f2a6b97ad..13575e10b 100644
--- a/apt-pkg/deb/debmetaindex.cc
+++ b/apt-pkg/deb/debmetaindex.cc
@@ -109,7 +109,7 @@ class APT_HIDDEN debReleaseIndexPrivate					/*{{{*/
    std::vector<std::string> SupportedComponents;
    std::map<std::string, std::string> const ReleaseOptions;
 
-   debReleaseIndexPrivate(std::map<std::string, std::string> const &Options) : CheckValidUntil(metaIndex::TRI_UNSET), ValidUntilMin(0), ValidUntilMax(0), CheckDate(metaIndex::TRI_UNSET), DateMaxFuture(0), NotBefore(0), ReleaseOptions(Options) {}
+   explicit debReleaseIndexPrivate(std::map<std::string, std::string> const &Options) : CheckValidUntil(metaIndex::TRI_UNSET), ValidUntilMin(0), ValidUntilMax(0), CheckDate(metaIndex::TRI_UNSET), DateMaxFuture(0), NotBefore(0), ReleaseOptions(Options) {}
 };
 									/*}}}*/
 // ReleaseIndex::MetaIndex* - display helpers				/*{{{*/
diff --git a/apt-pkg/deb/debrecords.h b/apt-pkg/deb/debrecords.h
index 7c3b9020c..ea3fc320a 100644
--- a/apt-pkg/deb/debrecords.h
+++ b/apt-pkg/deb/debrecords.h
@@ -85,7 +85,7 @@ class APT_HIDDEN debDebFileRecordParser : public debRecordParserBase
  public:
    virtual std::string FileName() APT_OVERRIDE;
 
-   debDebFileRecordParser(std::string FileName);
+   explicit debDebFileRecordParser(std::string FileName);
    virtual ~debDebFileRecordParser();
 };
 
diff --git a/apt-pkg/deb/dpkgpm.h b/apt-pkg/deb/dpkgpm.h
index 67c141766..3ba4770e8 100644
--- a/apt-pkg/deb/dpkgpm.h
+++ b/apt-pkg/deb/dpkgpm.h
@@ -131,7 +131,7 @@ class pkgDPkgPM : public pkgPackageManager
    
    public:
 
-   pkgDPkgPM(pkgDepCache *Cache);
+   explicit pkgDPkgPM(pkgDepCache *Cache);
    virtual ~pkgDPkgPM();
 
    APT_HIDDEN static bool ExpandPendingCalls(std::vector<Item> &List, pkgDepCache &Cache);
diff --git a/apt-pkg/edsp/edspindexfile.h b/apt-pkg/edsp/edspindexfile.h
index 4ac0f9d72..8fa8fdd60 100644
--- a/apt-pkg/edsp/edspindexfile.h
+++ b/apt-pkg/edsp/edspindexfile.h
@@ -29,7 +29,7 @@ public:
    virtual bool Exists() const APT_OVERRIDE;
    virtual bool HasPackages() const APT_OVERRIDE;
 
-   edspLikeIndex(std::string const &File);
+   explicit edspLikeIndex(std::string const &File);
    virtual ~edspLikeIndex();
 };
 
@@ -42,7 +42,7 @@ protected:
 public:
    virtual const Type *GetType() const APT_OVERRIDE APT_PURE;
 
-   edspIndex(std::string const &File);
+   explicit edspIndex(std::string const &File);
    virtual ~edspIndex();
 };
 
@@ -55,7 +55,7 @@ protected:
 public:
    virtual const Type *GetType() const APT_OVERRIDE APT_PURE;
 
-   eippIndex(std::string const &File);
+   explicit eippIndex(std::string const &File);
    virtual ~eippIndex();
 };
 
diff --git a/apt-pkg/edsp/edsplistparser.h b/apt-pkg/edsp/edsplistparser.h
index 59c759f9d..8f56f8abf 100644
--- a/apt-pkg/edsp/edsplistparser.h
+++ b/apt-pkg/edsp/edsplistparser.h
@@ -35,7 +35,7 @@ class APT_HIDDEN edspLikeListParser : public debListParser
    virtual APT::StringView Description_md5() APT_OVERRIDE;
    virtual unsigned short VersionHash() APT_OVERRIDE;
 
-   edspLikeListParser(FileFd *File);
+   explicit edspLikeListParser(FileFd *File);
    virtual ~edspLikeListParser();
 };
 
@@ -48,7 +48,7 @@ protected:
    virtual bool ParseStatus(pkgCache::PkgIterator &Pkg,pkgCache::VerIterator &Ver) APT_OVERRIDE;
 
 public:
-   edspListParser(FileFd *File);
+   explicit edspListParser(FileFd *File);
    virtual ~edspListParser();
 };
 
@@ -58,7 +58,7 @@ protected:
    virtual bool ParseStatus(pkgCache::PkgIterator &Pkg,pkgCache::VerIterator &Ver) APT_OVERRIDE;
 
 public:
-   eippListParser(FileFd *File);
+   explicit eippListParser(FileFd *File);
    virtual ~eippListParser();
 };
 #endif
diff --git a/apt-pkg/edsp/edspsystem.h b/apt-pkg/edsp/edspsystem.h
index 0855bb53f..8f5452dcb 100644
--- a/apt-pkg/edsp/edspsystem.h
+++ b/apt-pkg/edsp/edspsystem.h
@@ -37,7 +37,7 @@ public:
    virtual bool FindIndex(pkgCache::PkgFileIterator File,
 			  pkgIndexFile *&Found) const APT_OVERRIDE;
 
-   edspLikeSystem(char const * const Label);
+   explicit edspLikeSystem(char const * const Label);
    virtual ~edspLikeSystem();
 };
 
diff --git a/apt-private/private-cacheset.h b/apt-private/private-cacheset.h
index 3370bd03a..c52df36d7 100644
--- a/apt-private/private-cacheset.h
+++ b/apt-private/private-cacheset.h
@@ -18,6 +18,8 @@ class VerIteratorWithCaching
    const pkgCache::VerIterator iter;
    const pkgCache::DescFile * descFile;
 public:
+
+   // cppcheck-suppress noExplicitConstructor
    VerIteratorWithCaching(const pkgCache::VerIterator& iter) :
       iter(iter),
       descFile(iter->DescriptionList != 0
diff --git a/apt-private/private-json-hooks.cc b/apt-private/private-json-hooks.cc
index 65ff87924..3e0d8c93b 100644
--- a/apt-private/private-json-hooks.cc
+++ b/apt-private/private-json-hooks.cc
@@ -79,7 +79,7 @@ class APT_HIDDEN JsonWriter
    }
 
    public:
-   JsonWriter(std::ostream &os) : os(os) { old_locale = os.imbue(std::locale::classic()); }
+   explicit JsonWriter(std::ostream &os) : os(os) { old_locale = os.imbue(std::locale::classic()); }
    ~JsonWriter() { os.imbue(old_locale); }
    JsonWriter &beginArray()
    {
diff --git a/apt-private/private-sources.cc b/apt-private/private-sources.cc
index 713327f02..4cfb87938 100644
--- a/apt-private/private-sources.cc
+++ b/apt-private/private-sources.cc
@@ -31,7 +31,7 @@
 class APT_HIDDEN ScopedGetLock {
 public:
    int fd;
-   ScopedGetLock(std::string const &filename) : fd(GetLock(filename)) {}
+   explicit ScopedGetLock(std::string const &filename) : fd(GetLock(filename)) {}
    ~ScopedGetLock() { close(fd); }
 };
 bool EditSources(CommandLine &CmdL)
diff --git a/methods/mirror.cc b/methods/mirror.cc
index add9f0875..dcf4cbd13 100644
--- a/methods/mirror.cc
+++ b/methods/mirror.cc
@@ -97,7 +97,7 @@ class MirrorMethod : public aptMethod /*{{{*/
    void DealWithPendingItems(std::vector<std::string> const &baseuris, MirrorListInfo const &info, FetchItem *const Itm, std::function<void()> handler);
 
    public:
-   MirrorMethod(std::string &&pProg) : aptMethod(std::move(pProg), "2.0", SingleInstance | Pipeline | SendConfig | AuxRequests), genrng(clock())
+   explicit MirrorMethod(std::string &&pProg) : aptMethod(std::move(pProg), "2.0", SingleInstance | Pipeline | SendConfig | AuxRequests), genrng(clock())
    {
       SeccompFlags = aptMethod::BASE | aptMethod::DIRECTORY;
    }