diff --git a/src/MANYBODY/pair_adp.cpp b/src/MANYBODY/pair_adp.cpp
index 6bc0ab587b..23cff55ca2 100644
--- a/src/MANYBODY/pair_adp.cpp
+++ b/src/MANYBODY/pair_adp.cpp
@@ -554,7 +554,7 @@ void PairADP::read_file(char *filename)
       ValueTokenizer values = reader.next_values(1);
       file->nelements = values.next_int();
 
-      if (values.count() != file->nelements + 1)
+      if ((int)values.count() != file->nelements + 1)
         error->one(FLERR,"Incorrect element names in ADP potential file");
 
       file->elements = new char*[file->nelements];
diff --git a/src/MANYBODY/pair_airebo.cpp b/src/MANYBODY/pair_airebo.cpp
index df90609e7d..73af9e1acf 100644
--- a/src/MANYBODY/pair_airebo.cpp
+++ b/src/MANYBODY/pair_airebo.cpp
@@ -3488,7 +3488,7 @@ void PairAIREBO::read_file(char *filename)
       // global parameters
       current_section = "global parameters";
 
-      for(int i = 0; i < params.size(); i++) {
+      for(int i = 0; i < (int)params.size(); i++) {
         *params[i] = reader.next_double();
       }
 
diff --git a/src/MANYBODY/pair_comb3.cpp b/src/MANYBODY/pair_comb3.cpp
index a71edccab0..5b039c8eb5 100644
--- a/src/MANYBODY/pair_comb3.cpp
+++ b/src/MANYBODY/pair_comb3.cpp
@@ -312,7 +312,7 @@ double PairComb3::init_one(int i, int j)
 
 void PairComb3::read_lib()
 {
-  int i,j,k,l,m;
+  int i,j,k,l;
   int ii,jj,kk,ll,mm,iii;
 
   // open library file on proc 0
diff --git a/src/MANYBODY/pair_eam.cpp b/src/MANYBODY/pair_eam.cpp
index ec409d1786..984075d407 100644
--- a/src/MANYBODY/pair_eam.cpp
+++ b/src/MANYBODY/pair_eam.cpp
@@ -469,8 +469,6 @@ void PairEAM::read_file(char *filename)
     PotentialFileReader reader(lmp, filename, "EAM");
 
     try {
-      char * line = nullptr;
-
       reader.skip_line();
 
       ValueTokenizer values = reader.next_values(2);
diff --git a/src/MANYBODY/pair_eam_alloy.cpp b/src/MANYBODY/pair_eam_alloy.cpp
index d164682e9e..42587e9434 100644
--- a/src/MANYBODY/pair_eam_alloy.cpp
+++ b/src/MANYBODY/pair_eam_alloy.cpp
@@ -130,7 +130,7 @@ void PairEAMAlloy::read_file(char *filename)
       ValueTokenizer values = reader.next_values(1);
       file->nelements = values.next_int();
 
-      if (values.count() != file->nelements + 1)
+      if ((int)values.count() != file->nelements + 1)
         error->one(FLERR,"Incorrect element names in EAM potential file");
 
       file->elements = new char*[file->nelements];
diff --git a/src/MANYBODY/pair_eam_cd.cpp b/src/MANYBODY/pair_eam_cd.cpp
index 076f6d5e7d..eb8fc4e768 100644
--- a/src/MANYBODY/pair_eam_cd.cpp
+++ b/src/MANYBODY/pair_eam_cd.cpp
@@ -518,7 +518,7 @@ void PairEAMCD::read_h_coeff(char *filename)
     int degree = values.next_int();
     nhcoeff = degree+1;
 
-    if (values.count() != nhcoeff + 1 || nhcoeff < 1)
+    if ((int)values.count() != nhcoeff + 1 || nhcoeff < 1)
       error->one(FLERR, "Failed to read h(x) function coefficients in EAM file.");
 
     hcoeff = new double[nhcoeff];
diff --git a/src/MANYBODY/pair_eam_fs.cpp b/src/MANYBODY/pair_eam_fs.cpp
index 5d2339c4b5..448a1d2701 100644
--- a/src/MANYBODY/pair_eam_fs.cpp
+++ b/src/MANYBODY/pair_eam_fs.cpp
@@ -122,8 +122,6 @@ void PairEAMFS::read_file(char *filename)
     PotentialFileReader reader(lmp, filename, "EAM");
 
     try {
-      char * line = nullptr;
-
       reader.skip_line();
       reader.skip_line();
       reader.skip_line();
@@ -132,7 +130,7 @@ void PairEAMFS::read_file(char *filename)
       ValueTokenizer values = reader.next_values(1);
       file->nelements = values.next_int();
 
-      if (values.count() != file->nelements + 1)
+      if ((int)values.count() != file->nelements + 1)
         error->one(FLERR,"Incorrect element names in EAM potential file");
 
       file->elements = new char*[file->nelements];
diff --git a/src/USER-OMP/pair_eam_alloy_omp.cpp b/src/USER-OMP/pair_eam_alloy_omp.cpp
index ea2130721b..e8f56a9700 100644
--- a/src/USER-OMP/pair_eam_alloy_omp.cpp
+++ b/src/USER-OMP/pair_eam_alloy_omp.cpp
@@ -130,7 +130,7 @@ void PairEAMAlloyOMP::read_file(char *filename)
       ValueTokenizer values = reader.next_values(1);
       file->nelements = values.next_int();
 
-      if (values.count() != file->nelements + 1)
+      if ((int)values.count() != file->nelements + 1)
         error->one(FLERR,"Incorrect element names in EAM potential file");
 
       file->elements = new char*[file->nelements];
diff --git a/src/USER-OMP/pair_eam_fs_omp.cpp b/src/USER-OMP/pair_eam_fs_omp.cpp
index 71d58469c8..c68d5f6019 100644
--- a/src/USER-OMP/pair_eam_fs_omp.cpp
+++ b/src/USER-OMP/pair_eam_fs_omp.cpp
@@ -130,7 +130,7 @@ void PairEAMFSOMP::read_file(char *filename)
       ValueTokenizer values = reader.next_values(1);
       file->nelements = values.next_int();
 
-      if (values.count() != file->nelements + 1)
+      if ((int)values.count() != file->nelements + 1)
         error->one(FLERR,"Incorrect element names in EAM potential file");
 
       file->elements = new char*[file->nelements];
diff --git a/src/comm.cpp b/src/comm.cpp
index 9102e2991d..b00308a6e5 100644
--- a/src/comm.cpp
+++ b/src/comm.cpp
@@ -256,7 +256,6 @@ void Comm::init_exchange()
   int nfix = modify->nfix;
   Fix **fix = modify->fix;
 
-  int onefix;
   maxexchange_fix = 0;
   for (int i = 0; i < nfix; i++)
     maxexchange_fix += fix[i]->maxexchange;
diff --git a/src/library.cpp b/src/library.cpp
index 7840567866..1cacf9e7d8 100644
--- a/src/library.cpp
+++ b/src/library.cpp
@@ -1667,7 +1667,7 @@ int lammps_style_name(void* ptr, char * category, int index, char * buffer, int
   Info info(lmp);
   auto styles = info.get_available_styles(category);
 
-  if (index < styles.size()) {
+  if (index < (int)styles.size()) {
     strncpy(buffer, styles[index].c_str(), max_size);
     return true;
   }
diff --git a/src/table_file_reader.cpp b/src/table_file_reader.cpp
index 194db8f8eb..2f3317cb2a 100644
--- a/src/table_file_reader.cpp
+++ b/src/table_file_reader.cpp
@@ -38,7 +38,7 @@ TableFileReader::~TableFileReader() {
 
 char * TableFileReader::find_section_start(const std::string & keyword) {
   char * line = nullptr;
-  while (line = reader->next_line()) {
+  while ((line = reader->next_line())) {
     ValueTokenizer values(line);
     std::string word = values.next_string();
 
diff --git a/src/utils.cpp b/src/utils.cpp
index a8dc4e308e..bf5896d6d6 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -498,7 +498,7 @@ std::string utils::get_potential_date(const std::string & path, const std::strin
   reader.ignore_comments = false;
   char * line = nullptr;
 
-  while (line = reader.next_line()) {
+  while ((line = reader.next_line())) {
     ValueTokenizer values(line);
     while (values.has_next()) {
       std::string word = values.next_string();