diff --git a/CondCore/AlignmentPlugins/interface/AlignmentPayloadInspectorHelper.h b/CondCore/AlignmentPlugins/interface/AlignmentPayloadInspectorHelper.h
index 3814fa6dcde52..80a44790c3c64 100644
--- a/CondCore/AlignmentPlugins/interface/AlignmentPayloadInspectorHelper.h
+++ b/CondCore/AlignmentPlugins/interface/AlignmentPayloadInspectorHelper.h
@@ -71,7 +71,9 @@ namespace AlignmentPI {
                                   PARTITION::TECp,
                                   PARTITION::TECm};
 
-  std::ostream& operator<<(std::ostream& o, PARTITION x) { return o << std::underlying_type<PARTITION>::type(x); }
+  inline std::ostream& operator<<(std::ostream& o, PARTITION x) {
+    return o << std::underlying_type<PARTITION>::type(x);
+  }
 
   enum regions {
     BPixL1o,          //0  Barrel Pixel Layer 1 outer
@@ -149,7 +151,7 @@ namespace AlignmentPI {
   };
 
   /*--------------------------------------------------------------------*/
-  std::string getStringFromRegionEnum(AlignmentPI::regions e)
+  inline std::string getStringFromRegionEnum(AlignmentPI::regions e)
   /*--------------------------------------------------------------------*/
   {
     switch (e) {
@@ -300,7 +302,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  bool isBPixOuterLadder(const DetId& detid, const TrackerTopology& tTopo, bool isPhase0)
+  inline bool isBPixOuterLadder(const DetId& detid, const TrackerTopology& tTopo, bool isPhase0)
   /*--------------------------------------------------------------------*/
   {
     bool isOuter = false;
@@ -344,7 +346,7 @@ namespace AlignmentPI {
   };
 
   /*--------------------------------------------------------------------*/
-  void topolInfo::printAll()
+  inline void topolInfo::printAll()
   /*--------------------------------------------------------------------*/
   {
     std::cout << " detId:" << m_rawid << " subdetid: " << m_subdetid << " layer: " << m_layer << " side: " << m_side
@@ -353,7 +355,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void topolInfo::init()
+  inline void topolInfo::init()
   /*--------------------------------------------------------------------*/
   {
     m_rawid = 0;
@@ -367,7 +369,7 @@ namespace AlignmentPI {
   };
 
   /*--------------------------------------------------------------------*/
-  bool topolInfo::sanityCheck()
+  inline bool topolInfo::sanityCheck()
   /*--------------------------------------------------------------------*/
   {
     if (m_layer == 0 || (m_subdetid == 1 && m_layer > 4) || (m_subdetid == 2 && m_layer > 3)) {
@@ -377,7 +379,7 @@ namespace AlignmentPI {
     }
   }
   /*--------------------------------------------------------------------*/
-  void topolInfo::fillGeometryInfo(const DetId& detId, const TrackerTopology& tTopo, bool isPhase0)
+  inline void topolInfo::fillGeometryInfo(const DetId& detId, const TrackerTopology& tTopo, bool isPhase0)
   /*--------------------------------------------------------------------*/
   {
     unsigned int subdetId = static_cast<unsigned int>(detId.subdetId());
@@ -424,7 +426,7 @@ namespace AlignmentPI {
   // ------------ method to assign a partition based on the topology struct info ---------------
 
   /*--------------------------------------------------------------------*/
-  AlignmentPI::regions topolInfo::filterThePartition()
+  inline AlignmentPI::regions topolInfo::filterThePartition()
   /*--------------------------------------------------------------------*/
   {
     AlignmentPI::regions ret = AlignmentPI::NUM_OF_REGIONS;
@@ -594,7 +596,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::string getStringFromCoordinate(AlignmentPI::coordinate coord)
+  inline std::string getStringFromCoordinate(AlignmentPI::coordinate coord)
   /*--------------------------------------------------------------------*/
   {
     switch (coord) {
@@ -616,7 +618,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::string getStringFromIndex(AlignmentPI::index i)
+  inline std::string getStringFromIndex(AlignmentPI::index i)
   /*--------------------------------------------------------------------*/
   {
     switch (i) {
@@ -638,7 +640,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::string getStringFromPart(AlignmentPI::partitions i)
+  inline std::string getStringFromPart(AlignmentPI::partitions i)
   /*--------------------------------------------------------------------*/
   {
     switch (i) {
@@ -660,7 +662,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::pair<int, int> getIndices(AlignmentPI::index i)
+  inline std::pair<int, int> getIndices(AlignmentPI::index i)
   /*--------------------------------------------------------------------*/
   {
     switch (i) {
@@ -682,7 +684,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void makeNicePlotStyle(TH1* hist, int color)
+  inline void makeNicePlotStyle(TH1* hist, int color)
   /*--------------------------------------------------------------------*/
   {
     hist->SetStats(kFALSE);
@@ -707,7 +709,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void makeNiceStats(TH1F* hist, AlignmentPI::partitions part, int color)
+  inline void makeNiceStats(TH1F* hist, AlignmentPI::partitions part, int color)
   /*--------------------------------------------------------------------*/
   {
     char buffer[255];
@@ -740,7 +742,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::pair<float, float> getTheRange(std::map<uint32_t, float> values, const float nsigma)
+  inline std::pair<float, float> getTheRange(std::map<uint32_t, float> values, const float nsigma)
   /*--------------------------------------------------------------------*/
   {
     float sum = std::accumulate(
@@ -765,7 +767,7 @@ namespace AlignmentPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::pair<double, double> calculatePosition(TVirtualPad* myPad, int boundary)
+  inline std::pair<double, double> calculatePosition(TVirtualPad* myPad, int boundary)
   /*--------------------------------------------------------------------*/
   {
     int ix1;
@@ -850,16 +852,16 @@ namespace AlignmentPI {
   };
 
   /*--------------------------------------------------------------------*/
-  GlobalPoint TkAlBarycenters::getPartitionAvg(AlignmentPI::PARTITION p)
+  inline GlobalPoint TkAlBarycenters::getPartitionAvg(AlignmentPI::PARTITION p)
   /*--------------------------------------------------------------------*/
   {
     return GlobalPoint(Xbarycenters[p], Ybarycenters[p], Zbarycenters[p]);
   }
 
   /*--------------------------------------------------------------------*/
-  void TkAlBarycenters::computeBarycenters(const std::vector<AlignTransform>& input,
-                                           const TrackerTopology& tTopo,
-                                           const std::map<AlignmentPI::coordinate, float>& GPR)
+  inline void TkAlBarycenters::computeBarycenters(const std::vector<AlignTransform>& input,
+                                                  const TrackerTopology& tTopo,
+                                                  const std::map<AlignmentPI::coordinate, float>& GPR)
   /*--------------------------------------------------------------------*/
   {
     for (const auto& ali : input) {
diff --git a/CondCore/BeamSpotPlugins/interface/BeamSpotPayloadInspectorHelper.h b/CondCore/BeamSpotPlugins/interface/BeamSpotPayloadInspectorHelper.h
index 37cb68ed40ef7..a0d992f6ee90e 100644
--- a/CondCore/BeamSpotPlugins/interface/BeamSpotPayloadInspectorHelper.h
+++ b/CondCore/BeamSpotPlugins/interface/BeamSpotPayloadInspectorHelper.h
@@ -20,7 +20,7 @@
 
 namespace BeamSpotPI {
 
-  std::pair<unsigned int, unsigned int> unpack(cond::Time_t since) {
+  inline std::pair<unsigned int, unsigned int> unpack(cond::Time_t since) {
     auto kLowMask = 0XFFFFFFFF;
     auto run = (since >> 32);
     auto lumi = (since & kLowMask);
@@ -46,7 +46,7 @@ namespace BeamSpotPI {
   };
 
   /************************************************/
-  std::string getStringFromParamEnum(const parameters& parameter) {
+  inline std::string getStringFromParamEnum(const parameters& parameter) {
     switch (parameter) {
       case X:
         return "X";
diff --git a/CondCore/EcalPlugins/plugins/ESDrawUtils.h b/CondCore/EcalPlugins/plugins/ESDrawUtils.h
index 0531c44975194..8e74c5a7c2b57 100644
--- a/CondCore/EcalPlugins/plugins/ESDrawUtils.h
+++ b/CondCore/EcalPlugins/plugins/ESDrawUtils.h
@@ -1,7 +1,7 @@
 #include "TH2F.h"
 #include "TLine.h"
 
-void DrawES(int plane, int side) {
+inline void DrawES(int plane, int side) {
   int ixF[172] = {
       2,  2,  3,  3,  4,  4,  5,  5,  6,  6,  7,  7,  8,  8,  10, 10, 11, 11, 14, 14,     // external upper crown (44)
       16, 16, 26, 26, 28, 28, 31, 31, 32, 32, 34, 34, 35, 35, 36, 36, 37, 37, 38, 38,     // external upper crown
diff --git a/CondCore/EcalPlugins/plugins/EcalDrawUtils.h b/CondCore/EcalPlugins/plugins/EcalDrawUtils.h
index 855cd7e09c7bc..8c2dcc9190441 100644
--- a/CondCore/EcalPlugins/plugins/EcalDrawUtils.h
+++ b/CondCore/EcalPlugins/plugins/EcalDrawUtils.h
@@ -1,7 +1,7 @@
 #include "TH2F.h"
 #include "TLine.h"
 
-void DrawEB(TH2F* ebmap, float min, float max) {
+inline void DrawEB(TH2F* ebmap, float min, float max) {
   ebmap->SetXTitle("i#phi");
   ebmap->SetYTitle("i#eta");
   ebmap->GetXaxis()->SetNdivisions(-418, kFALSE);
@@ -26,7 +26,7 @@ void DrawEB(TH2F* ebmap, float min, float max) {
   l->Draw();
 }  //   DrawEB method
 
-void DrawEE(TH2F* endc, float min, float max) {
+inline void DrawEE(TH2F* endc, float min, float max) {
   int ixSectorsEE[202] = {
       62, 62, 61, 61, 60, 60, 59, 59, 58, 58, 56, 56, 46, 46, 44, 44, 43, 43, 42, 42,  41,  41,  40,  40, 41, 41,
       42, 42, 43, 43, 44, 44, 46, 46, 56, 56, 58, 58, 59, 59, 60, 60, 61, 61, 62, 62,  0,   101, 101, 98, 98, 96,
@@ -62,7 +62,7 @@ void DrawEE(TH2F* endc, float min, float max) {
   }
 }  //   DrawEE method
 
-void DrawEE_Tower(TH2F* endc, TLine* l, double minScale, double maxScale) {
+inline void DrawEE_Tower(TH2F* endc, TLine* l, double minScale, double maxScale) {
   endc->SetStats(false);
   endc->SetMinimum(minScale);
   endc->SetMaximum(maxScale);
@@ -88,7 +88,7 @@ void DrawEE_Tower(TH2F* endc, TLine* l, double minScale, double maxScale) {
 
 }  //draw EE in case of a tower
 
-void drawTable(int nbRows, int nbColumns) {
+inline void drawTable(int nbRows, int nbColumns) {
   TLine* l = new TLine;
   l->SetLineWidth(1);
   for (int i = 1; i < nbRows; i++) {
diff --git a/CondCore/EcalPlugins/plugins/EcalFloatCondObjectContainerUtils.h b/CondCore/EcalPlugins/plugins/EcalFloatCondObjectContainerUtils.h
index a1068a5a7bfe8..2b1f07a87c7a5 100644
--- a/CondCore/EcalPlugins/plugins/EcalFloatCondObjectContainerUtils.h
+++ b/CondCore/EcalPlugins/plugins/EcalFloatCondObjectContainerUtils.h
@@ -166,14 +166,14 @@ void fillEEMap_TwoIOVs(std::shared_ptr<floatCondObj> payload,
         }  // validDetId
 }
 
-void fillTableWithSummary(TH2F*& align,
-                          std::string title,
-                          const float& mean_x_EB,
-                          const float& rms_EB,
-                          const int& num_x_EB,
-                          const float& mean_x_EE,
-                          const float& rms_EE,
-                          const int& num_x_EE) {
+inline void fillTableWithSummary(TH2F*& align,
+                                 std::string title,
+                                 const float& mean_x_EB,
+                                 const float& rms_EB,
+                                 const int& num_x_EB,
+                                 const float& mean_x_EE,
+                                 const float& rms_EE,
+                                 const int& num_x_EE) {
   int NbRows = 2;
   align = new TH2F(title.c_str(), "EB/EE      mean_x      rms        num_x", 4, 0, 4, NbRows, 0, NbRows);
 
diff --git a/CondCore/EcalPlugins/plugins/EcalFunctionParametersUtils.h b/CondCore/EcalPlugins/plugins/EcalFunctionParametersUtils.h
index 35624944bbad5..36933eb47dffd 100644
--- a/CondCore/EcalPlugins/plugins/EcalFunctionParametersUtils.h
+++ b/CondCore/EcalPlugins/plugins/EcalFunctionParametersUtils.h
@@ -2,7 +2,7 @@
 #include <string>
 #include <cmath>
 
-int countEmptyRows(std::vector<float>& vec) {
+inline int countEmptyRows(std::vector<float>& vec) {
   int cnt = 0;
   for (std::vector<float>::const_iterator it = vec.begin(); it != vec.end(); it++)
     if ((*it) == 0.0f)
@@ -11,7 +11,7 @@ int countEmptyRows(std::vector<float>& vec) {
   return cnt;
 }
 
-void fillFunctionParamsValues(
+inline void fillFunctionParamsValues(
     TH2F*& align, std::vector<float>& m_params, std::string title, int& gridRows, int& NbColumns) {
   const int maxInCol = 25;
   int NbRows = 0;
diff --git a/CondCore/HcalPlugins/interface/HcalObjRepresent.h b/CondCore/HcalPlugins/interface/HcalObjRepresent.h
index 489aab34c5b52..6f70e6f7a43ad 100644
--- a/CondCore/HcalPlugins/interface/HcalObjRepresent.h
+++ b/CondCore/HcalPlugins/interface/HcalObjRepresent.h
@@ -481,7 +481,7 @@ namespace HcalObjRepresent {
     }
   };
 
-  void drawTable(int nbRows, int nbColumns) {
+  inline void drawTable(int nbRows, int nbColumns) {
     TLine* l = new TLine;
     l->SetLineWidth(1);
     for (int i = 1; i < nbRows; i++) {
@@ -498,7 +498,7 @@ namespace HcalObjRepresent {
     }
   }
 
-  std::string SciNotatStr(float num) {
+  inline std::string SciNotatStr(float num) {
     // Create an output string stream
     std::ostringstream streamObj2;
 
@@ -528,12 +528,12 @@ namespace HcalObjRepresent {
     return ss.str();
   }
 
-  const bool isBitSet(unsigned int bitnumber, unsigned int status) {
+  inline const bool isBitSet(unsigned int bitnumber, unsigned int status) {
     unsigned int statadd = 0x1 << (bitnumber);
     return (status & statadd) ? (true) : (false);
   }
 
-  std::string getBitsSummary(uint32_t bits, std::string statusBitArray[], short unsigned int bitMap[]) {
+  inline std::string getBitsSummary(uint32_t bits, std::string statusBitArray[], short unsigned int bitMap[]) {
     std::stringstream ss;
     for (unsigned int i = 0; i < 9; ++i) {
       if (isBitSet(bitMap[i], bits)) {
@@ -545,7 +545,7 @@ namespace HcalObjRepresent {
   }
 
   //functions for making plot:
-  void setBinLabels(std::vector<TH2F>& depth) {
+  inline void setBinLabels(std::vector<TH2F>& depth) {
     // Set labels for all depth histograms
     for (unsigned int i = 0; i < depth.size(); ++i) {
       depth[i].SetXTitle("i#eta");
@@ -1050,7 +1050,7 @@ namespace HcalObjRepresent {
   }  // FillUnphysicalHEHFBins(std::vector<MonitorElement*> &hh)
 
   // special fill call based on detid -- eventually will need special treatment
-  void Fill(HcalDetId& id, double val /*=1*/, std::vector<TH2F>& depth) {
+  inline void Fill(HcalDetId& id, double val /*=1*/, std::vector<TH2F>& depth) {
     // If in HF, need to shift by 1 bin (-1 bin lower in -HF, +1 bin higher in +HF)
     if (id.subdet() == HcalForward)
       depth[id.depth() - 1].Fill(id.ieta() < 0 ? id.ieta() - 1 : id.ieta() + 1, id.iphi(), val);
@@ -1058,14 +1058,14 @@ namespace HcalObjRepresent {
       depth[id.depth() - 1].Fill(id.ieta(), id.iphi(), val);
   }
 
-  void Reset(std::vector<TH2F>& depth) {
+  inline void Reset(std::vector<TH2F>& depth) {
     for (unsigned int d = 0; d < depth.size(); d++)
       //BUG CAN BE HERE:
       //if(depth[d])
       depth[d].Reset();
   }  // void Reset(void)
 
-  void setup(std::vector<TH2F>& depth, std::string name, std::string units = "") {
+  inline void setup(std::vector<TH2F>& depth, std::string name, std::string units = "") {
     std::string unittitle, unitname;
     if (units.empty()) {
       unitname = units;
@@ -1132,11 +1132,11 @@ namespace HcalObjRepresent {
     setBinLabels(depth);  // set axis titles, special bins
   }
 
-  void fillOneGain(std::vector<TH2F>& graphData,
-                   HcalGains::tAllContWithNames& allContainers,
-                   std::string name,
-                   int id,
-                   std::string units = "") {
+  inline void fillOneGain(std::vector<TH2F>& graphData,
+                          HcalGains::tAllContWithNames& allContainers,
+                          std::string name,
+                          int id,
+                          std::string units = "") {
     setup(graphData, name);
 
     std::stringstream x;
diff --git a/CondCore/RunInfoPlugins/interface/RunInfoPayloadInspectoHelper.h b/CondCore/RunInfoPlugins/interface/RunInfoPayloadInspectoHelper.h
index 04503b61c9c72..3ee96a6773ae2 100644
--- a/CondCore/RunInfoPlugins/interface/RunInfoPayloadInspectoHelper.h
+++ b/CondCore/RunInfoPlugins/interface/RunInfoPayloadInspectoHelper.h
@@ -36,7 +36,7 @@ namespace RunInfoPI {
   };
 
   /************************************************/
-  float theBField(const float current) {
+  inline float theBField(const float current) {
     // logic is taken from https://github.com/cms-sw/cmssw/blob/master/MagneticField/GeomBuilder/plugins/VolumeBasedMagneticFieldESProducerFromDB.cc#L156
 
     int i = 0;
@@ -49,7 +49,7 @@ namespace RunInfoPI {
   }
 
   /************************************************/
-  float runDuration(const std::shared_ptr<RunInfo>& payload) {
+  inline float runDuration(const std::shared_ptr<RunInfo>& payload) {
     // calculation of the run duration in seconds
     time_t start_time = payload->m_start_time_ll;
     ctime(&start_time);
@@ -59,19 +59,19 @@ namespace RunInfoPI {
   }
 
   /************************************************/
-  std::string runStartTime(const std::shared_ptr<RunInfo>& payload) {
+  inline std::string runStartTime(const std::shared_ptr<RunInfo>& payload) {
     const time_t start_time = payload->m_start_time_ll / 1.0e+6;
     return std::asctime(std::gmtime(&start_time));
   }
 
   /************************************************/
-  std::string runEndTime(const std::shared_ptr<RunInfo>& payload) {
+  inline std::string runEndTime(const std::shared_ptr<RunInfo>& payload) {
     const time_t end_time = payload->m_stop_time_ll / 1.0e+6;
     return std::asctime(std::gmtime(&end_time));
   }
 
   /************************************************/
-  std::string getStringFromTypeEnum(const parameters& parameter) {
+  inline std::string getStringFromTypeEnum(const parameters& parameter) {
     switch (parameter) {
       case m_run:
         return "run number";
@@ -101,7 +101,7 @@ namespace RunInfoPI {
   }
 
   /************************************************/
-  void reportSummaryMapPalette(TH2* obj) {
+  inline void reportSummaryMapPalette(TH2* obj) {
     static int pcol[20];
 
     float rgb[20][3];
diff --git a/CondCore/SiPixelPlugins/interface/PixelRegionContainers.h b/CondCore/SiPixelPlugins/interface/PixelRegionContainers.h
index 51f01e1502551..9965eb7c3d51a 100644
--- a/CondCore/SiPixelPlugins/interface/PixelRegionContainers.h
+++ b/CondCore/SiPixelPlugins/interface/PixelRegionContainers.h
@@ -15,7 +15,7 @@
 
 namespace PixelRegions {
 
-  std::string itoa(int i) {
+  inline std::string itoa(int i) {
     char temp[20];
     sprintf(temp, "%d", i);
     return ((std::string)temp);
diff --git a/CondCore/SiPixelPlugins/interface/SiPixelPayloadInspectorHelper.h b/CondCore/SiPixelPlugins/interface/SiPixelPayloadInspectorHelper.h
index e37d5a04c96b2..69b6c6535d620 100644
--- a/CondCore/SiPixelPlugins/interface/SiPixelPayloadInspectorHelper.h
+++ b/CondCore/SiPixelPlugins/interface/SiPixelPayloadInspectorHelper.h
@@ -111,7 +111,7 @@ namespace SiPixelPI {
   };
 
   //============================================================================
-  std::pair<unsigned int, unsigned int> unpack(cond::Time_t since) {
+  inline std::pair<unsigned int, unsigned int> unpack(cond::Time_t since) {
     auto kLowMask = 0XFFFFFFFF;
     auto run = (since >> 32);
     auto lumi = (since & kLowMask);
@@ -121,7 +121,7 @@ namespace SiPixelPI {
   //============================================================================
   // Taken from pixel naming classes
   // BmO (-z-x) = 1, BmI (-z+x) = 2 , BpO (+z-x) = 3 , BpI (+z+x) = 4
-  int quadrant(const DetId& detid, const TrackerTopology* tTopo_, bool phase_) {
+  inline int quadrant(const DetId& detid, const TrackerTopology* tTopo_, bool phase_) {
     if (detid.subdetId() == PixelSubdetector::PixelBarrel) {
       return PixelBarrelName(detid, tTopo_, phase_).shell();
     } else {
@@ -132,7 +132,7 @@ namespace SiPixelPI {
   //============================================================================
   // Online ladder convention taken from pixel naming class for barrel
   // Apply sign convention (- sign for BmO and BpO)
-  int signed_ladder(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
+  inline int signed_ladder(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
     if (detid.subdetId() != PixelSubdetector::PixelBarrel)
       return -9999;
     int signed_ladder = PixelBarrelName(detid, &tTopo_, phase_).ladderName();
@@ -144,7 +144,7 @@ namespace SiPixelPI {
   //============================================================================
   // Online mdoule convention taken from pixel naming class for barrel
   // Apply sign convention (- sign for BmO and BmI)
-  int signed_module(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
+  inline int signed_module(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
     if (detid.subdetId() != PixelSubdetector::PixelBarrel)
       return -9999;
     int signed_module = PixelBarrelName(detid, &tTopo_, phase_).moduleName();
@@ -160,7 +160,7 @@ namespace SiPixelPI {
   //   Panel 1 plq 1-2, Panel 2, plq 1   = Ring 1
   //   Panel 1 plq 3-4, Panel 2, plq 2-3 = Ring 2
   // Phase 1: Using pixel naming class for endcap
-  int ring(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
+  inline int ring(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
     if (detid.subdetId() != PixelSubdetector::PixelEndcap)
       return -9999;
     int ring = -9999;
@@ -175,7 +175,7 @@ namespace SiPixelPI {
   //============================================================================
   // Online blade convention taken from pixel naming class for endcap
   // Apply sign convention (- sign for BmO and BpO)
-  int signed_blade(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
+  inline int signed_blade(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
     if (detid.subdetId() != PixelSubdetector::PixelEndcap)
       return -9999;
     int signed_blade = PixelEndcapName(detid, &tTopo_, phase_).bladeName();
@@ -185,7 +185,7 @@ namespace SiPixelPI {
   }
 
   //============================================================================
-  int signed_blade_panel(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
+  inline int signed_blade_panel(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
     if (detid.subdetId() != PixelSubdetector::PixelEndcap)
       return -9999;
     int signed_blade_panel = signed_blade(detid, tTopo_, phase_) + (tTopo_.pxfPanel(detid) - 1);
@@ -195,7 +195,7 @@ namespace SiPixelPI {
   //============================================================================
   // Online disk convention
   // Apply sign convention (- sign for BmO and BmI)
-  int signed_disk(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
+  inline int signed_disk(const DetId& detid, const TrackerTopology& tTopo_, bool phase_) {
     if (detid.subdetId() != PixelSubdetector::PixelEndcap)
       return -9999;
     int signed_disk = tTopo_.pxfDisk(DetId(detid));
@@ -205,7 +205,7 @@ namespace SiPixelPI {
   }
 
   //============================================================================
-  void draw_line(double x1, double x2, double y1, double y2, int width = 2, int style = 1, int color = 1) {
+  inline void draw_line(double x1, double x2, double y1, double y2, int width = 2, int style = 1, int color = 1) {
     TLine* l = new TLine(x1, y1, x2, y2);
     l->SetBit(kCanDelete);
     l->SetLineWidth(width);
@@ -215,14 +215,14 @@ namespace SiPixelPI {
   }
 
   //============================================================================
-  void dress_occup_plot(TCanvas& canv,
-                        TH2* h,
-                        int lay,
-                        int ring = 0,
-                        int phase = 0,
-                        bool half_shift = true,
-                        bool mark_zero = true,
-                        bool standard_palette = true) {
+  inline void dress_occup_plot(TCanvas& canv,
+                               TH2* h,
+                               int lay,
+                               int ring = 0,
+                               int phase = 0,
+                               bool half_shift = true,
+                               bool mark_zero = true,
+                               bool standard_palette = true) {
     std::string s_title;
 
     if (lay > 0) {
@@ -505,7 +505,7 @@ namespace SiPixelPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void adjustCanvasMargins(TVirtualPad* pad, float top, float bottom, float left, float right)
+  inline void adjustCanvasMargins(TVirtualPad* pad, float top, float bottom, float left, float right)
   /*--------------------------------------------------------------------*/
   {
     if (top > 0)
@@ -519,7 +519,7 @@ namespace SiPixelPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void adjustStats(TPaveStats* stats, float X1, float Y1, float X2, float Y2)
+  inline void adjustStats(TPaveStats* stats, float X1, float Y1, float X2, float Y2)
   /*--------------------------------------------------------------------*/
   {
     stats->SetX1NDC(X1);  //new x start position
@@ -529,7 +529,7 @@ namespace SiPixelPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::pair<float, float> getExtrema(TH1* h1, TH1* h2)
+  inline std::pair<float, float> getExtrema(TH1* h1, TH1* h2)
   /*--------------------------------------------------------------------*/
   {
     float theMax(-9999.);
@@ -545,7 +545,7 @@ namespace SiPixelPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void makeNicePlotStyle(TH1* hist)
+  inline void makeNicePlotStyle(TH1* hist)
   /*--------------------------------------------------------------------*/
   {
     hist->SetStats(kFALSE);
@@ -593,7 +593,7 @@ namespace SiPixelPI {
   };
 
   /*--------------------------------------------------------------------*/
-  std::string getStringFromRegionEnum(SiPixelPI::regions e)
+  inline std::string getStringFromRegionEnum(SiPixelPI::regions e)
   /*--------------------------------------------------------------------*/
   {
     switch (e) {
@@ -632,7 +632,7 @@ namespace SiPixelPI {
   }
 
   /*--------------------------------------------------------------------*/
-  bool isBPixOuterLadder(const DetId& detid, const TrackerTopology& tTopo, bool isPhase0)
+  inline bool isBPixOuterLadder(const DetId& detid, const TrackerTopology& tTopo, bool isPhase0)
   /*--------------------------------------------------------------------*/
   {
     bool isOuter = false;
@@ -675,7 +675,7 @@ namespace SiPixelPI {
   };
 
   /*--------------------------------------------------------------------*/
-  void topolInfo::printAll()
+  inline void topolInfo::printAll()
   /*--------------------------------------------------------------------*/
   {
     std::cout << " detId:" << m_rawid << " subdetid: " << m_subdetid << " layer: " << m_layer << " side: " << m_side
@@ -683,7 +683,7 @@ namespace SiPixelPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void topolInfo::init()
+  inline void topolInfo::init()
   /*--------------------------------------------------------------------*/
   {
     m_rawid = 0;
@@ -695,7 +695,7 @@ namespace SiPixelPI {
   };
 
   /*--------------------------------------------------------------------*/
-  bool topolInfo::sanityCheck()
+  inline bool topolInfo::sanityCheck()
   /*--------------------------------------------------------------------*/
   {
     if (m_layer == 0 || (m_subdetid == 1 && m_layer > 4) || (m_subdetid == 2 && m_layer > 3)) {
@@ -705,7 +705,7 @@ namespace SiPixelPI {
     }
   }
   /*--------------------------------------------------------------------*/
-  void topolInfo::fillGeometryInfo(const DetId& detId, const TrackerTopology& tTopo, const SiPixelPI::phase& ph)
+  inline void topolInfo::fillGeometryInfo(const DetId& detId, const TrackerTopology& tTopo, const SiPixelPI::phase& ph)
   /*--------------------------------------------------------------------*/
   {
     // set the phase
@@ -727,7 +727,7 @@ namespace SiPixelPI {
   // ------------ method to assign a partition based on the topology struct info ---------------
 
   /*--------------------------------------------------------------------*/
-  SiPixelPI::regions topolInfo::filterThePartition()
+  inline SiPixelPI::regions topolInfo::filterThePartition()
   /*--------------------------------------------------------------------*/
   {
     SiPixelPI::regions ret = SiPixelPI::NUM_OF_REGIONS;
@@ -779,7 +779,7 @@ namespace SiPixelPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void displayNotSupported(TCanvas& canv, const unsigned int size)
+  inline void displayNotSupported(TCanvas& canv, const unsigned int size)
   /*--------------------------------------------------------------------*/
   {
     std::string phase = (size < SiPixelPI::phase1size) ? "Phase-0" : "Phase-2";
@@ -806,7 +806,7 @@ namespace SiPixelPI {
   }
 
   /*--------------------------------------------------------------------*/
-  bool checkAnswerOK(std::string& answer, bool& result)
+  inline bool checkAnswerOK(std::string& answer, bool& result)
   /*--------------------------------------------------------------------*/
   {
     std::transform(answer.begin(), answer.end(), answer.begin(), [](unsigned char x) { return ::tolower(x); });
diff --git a/CondCore/SiStripPlugins/interface/SiStripPayloadInspectorHelper.h b/CondCore/SiStripPlugins/interface/SiStripPayloadInspectorHelper.h
index a227de7772127..9c7c0165d99ef 100644
--- a/CondCore/SiStripPlugins/interface/SiStripPayloadInspectorHelper.h
+++ b/CondCore/SiStripPlugins/interface/SiStripPayloadInspectorHelper.h
@@ -169,7 +169,7 @@ namespace SiStripPI {
   enum estimator { min, max, mean, rms };
 
   /*--------------------------------------------------------------------*/
-  std::string estimatorType(SiStripPI::estimator e)
+  inline std::string estimatorType(SiStripPI::estimator e)
   /*--------------------------------------------------------------------*/
   {
     switch (e) {
@@ -187,7 +187,7 @@ namespace SiStripPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::string getStringFromSubdet(StripSubdetector::SubDetector sub)
+  inline std::string getStringFromSubdet(StripSubdetector::SubDetector sub)
   /*-------------------------------------------------------------------*/
   {
     switch (sub) {
@@ -247,7 +247,7 @@ namespace SiStripPI {
   };
 
   /*--------------------------------------------------------------------*/
-  std::pair<int, const char*> regionType(int index)
+  inline std::pair<int, const char*> regionType(int index)
   /*--------------------------------------------------------------------*/
   {
     auto region = static_cast<std::underlying_type_t<SiStripPI::TrackerRegion>>(index);
@@ -337,7 +337,7 @@ namespace SiStripPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::pair<float, float> getTheRange(std::map<uint32_t, float> values, const float nsigma)
+  inline std::pair<float, float> getTheRange(std::map<uint32_t, float> values, const float nsigma)
   /*--------------------------------------------------------------------*/
   {
     float sum = std::accumulate(
@@ -362,13 +362,13 @@ namespace SiStripPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void drawStatBox(std::map<std::string, std::shared_ptr<TH1F>> histos,
-                   std::map<std::string, int> colormap,
-                   std::vector<std::string> legend,
-                   double X = 0.15,
-                   double Y = 0.93,
-                   double W = 0.15,
-                   double H = 0.10)
+  inline void drawStatBox(std::map<std::string, std::shared_ptr<TH1F>> histos,
+                          std::map<std::string, int> colormap,
+                          std::vector<std::string> legend,
+                          double X = 0.15,
+                          double Y = 0.93,
+                          double W = 0.15,
+                          double H = 0.10)
   /*--------------------------------------------------------------------*/
   {
     char buffer[255];
@@ -399,7 +399,7 @@ namespace SiStripPI {
   }
 
   /*--------------------------------------------------------------------*/
-  std::pair<float, float> getExtrema(TH1* h1, TH1* h2)
+  inline std::pair<float, float> getExtrema(TH1* h1, TH1* h2)
   /*--------------------------------------------------------------------*/
   {
     float theMax(-9999.);
@@ -415,7 +415,7 @@ namespace SiStripPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void makeNicePlotStyle(TH1* hist)
+  inline void makeNicePlotStyle(TH1* hist)
   /*--------------------------------------------------------------------*/
   {
     hist->SetStats(kFALSE);
@@ -435,7 +435,7 @@ namespace SiStripPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void printSummary(const std::map<unsigned int, SiStripDetSummary::Values>& map)
+  inline void printSummary(const std::map<unsigned int, SiStripDetSummary::Values>& map)
   /*--------------------------------------------------------------------*/
   {
     for (const auto& element : map) {
@@ -476,7 +476,7 @@ namespace SiStripPI {
   // code is mutuated from CalibTracker/SiStripQuality/plugins/SiStripQualityStatistics
 
   /*--------------------------------------------------------------------*/
-  void setBadComponents(int i, int component, const SiStripQuality::BadComponent& BC, int NBadComponent[4][19][4])
+  inline void setBadComponents(int i, int component, const SiStripQuality::BadComponent& BC, int NBadComponent[4][19][4])
   /*--------------------------------------------------------------------*/
   {
     if (BC.BadApvs) {
@@ -497,9 +497,9 @@ namespace SiStripPI {
 
   // generic code to fill a SiStripDetSummary with Noise payload info
   /*--------------------------------------------------------------------*/
-  void fillNoiseDetSummary(SiStripDetSummary& summaryNoise,
-                           std::shared_ptr<SiStripNoises> payload,
-                           SiStripPI::estimator est)
+  inline void fillNoiseDetSummary(SiStripDetSummary& summaryNoise,
+                                  std::shared_ptr<SiStripNoises> payload,
+                                  SiStripPI::estimator est)
   /*--------------------------------------------------------------------*/
   {
     SiStripNoises::RegistryIterator rit = payload->getRegistryVectorBegin(), erit = payload->getRegistryVectorEnd();
@@ -557,7 +557,7 @@ namespace SiStripPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void fillTotalComponents(int NTkComponents[4], int NComponents[4][19][4], const TrackerTopology m_trackerTopo)
+  inline void fillTotalComponents(int NTkComponents[4], int NComponents[4][19][4], const TrackerTopology m_trackerTopo)
   /*--------------------------------------------------------------------*/
   {
     edm::FileInPath fp_ = edm::FileInPath("CalibTracker/SiStripCommon/data/SiStripDetInfo.dat");
@@ -609,10 +609,10 @@ namespace SiStripPI {
 
   // generic code to fill the vectors of bad components
   /*--------------------------------------------------------------------*/
-  void fillBCArrays(const SiStripQuality* siStripQuality_,
-                    int NTkBadComponent[4],
-                    int NBadComponent[4][19][4],
-                    const TrackerTopology m_trackerTopo)
+  inline void fillBCArrays(const SiStripQuality* siStripQuality_,
+                           int NTkBadComponent[4],
+                           int NBadComponent[4][19][4],
+                           const TrackerTopology m_trackerTopo)
   /*--------------------------------------------------------------------*/
   {
     std::vector<SiStripQuality::BadComponent> BC = siStripQuality_->getBadComponentList();
@@ -731,7 +731,7 @@ namespace SiStripPI {
   }
 
   /*--------------------------------------------------------------------*/
-  void printBCDebug(int NTkBadComponent[4], int NBadComponent[4][19][4])
+  inline void printBCDebug(int NTkBadComponent[4], int NBadComponent[4][19][4])
   /*--------------------------------------------------------------------*/
   {
     //&&&&&&&&&&&&&&&&&&
@@ -786,7 +786,7 @@ namespace SiStripPI {
   enum palette { HALFGRAY, GRAY, BLUES, REDS, ANTIGRAY, FIRE, ANTIFIRE, LOGREDBLUE, BLUERED, LOGBLUERED, DEFAULT };
 
   /*--------------------------------------------------------------------*/
-  void setPaletteStyle(SiStripPI::palette palette)
+  inline void setPaletteStyle(SiStripPI::palette palette)
   /*--------------------------------------------------------------------*/
   {
     TStyle* palettestyle = new TStyle("palettestyle", "Style for P-TDR");
diff --git a/CondFormats/JetMETObjects/interface/Utilities.h b/CondFormats/JetMETObjects/interface/Utilities.h
index 4396935368be0..3f64051bdadfa 100644
--- a/CondFormats/JetMETObjects/interface/Utilities.h
+++ b/CondFormats/JetMETObjects/interface/Utilities.h
@@ -107,7 +107,7 @@ namespace std {
 }  // namespace std
 
 namespace {
-  void handleError(const std::string& fClass, const std::string& fMessage) {
+  inline void handleError(const std::string& fClass, const std::string& fMessage) {
 #ifdef STANDALONE
     std::stringstream sserr;
     sserr << fClass << " ERROR: " << fMessage;
diff --git a/CondTools/Hcal/interface/HcalDbXml.h b/CondTools/Hcal/interface/HcalDbXml.h
index 7e031501e10e0..be3b23cddd00c 100644
--- a/CondTools/Hcal/interface/HcalDbXml.h
+++ b/CondTools/Hcal/interface/HcalDbXml.h
@@ -29,12 +29,12 @@ namespace HcalDbXml {
                   unsigned long fGMTIOVEnd,
                   const std::string& fTag,
                   const HcalPedestals& fObject);
-  bool dumpObject(std::ostream& fOutput,
-                  unsigned fRun,
-                  unsigned long fGMTIOVBegin,
-                  unsigned long fGMTIOVEnd,
-                  const std::string& fTag,
-                  const HcalPedestalWidths& fObject) {
+  inline bool dumpObject(std::ostream& fOutput,
+                         unsigned fRun,
+                         unsigned long fGMTIOVBegin,
+                         unsigned long fGMTIOVEnd,
+                         const std::string& fTag,
+                         const HcalPedestalWidths& fObject) {
     return false;
   }
   bool dumpObject(std::ostream& fOutput,