diff --git a/src/ASPHERE/compute_temp_asphere.cpp b/src/ASPHERE/compute_temp_asphere.cpp
index 2fe2e9699c..9afae4d2d9 100644
--- a/src/ASPHERE/compute_temp_asphere.cpp
+++ b/src/ASPHERE/compute_temp_asphere.cpp
@@ -58,9 +58,7 @@ ComputeTempAsphere::ComputeTempAsphere(LAMMPS *lmp, int narg, char **arg) :
       if (iarg+2 > narg)
         error->all(FLERR,"Illegal compute temp/asphere command");
       tempbias = 1;
-      int n = strlen(arg[iarg+1]) + 1;
-      id_bias = new char[n];
-      strcpy(id_bias,arg[iarg+1]);
+      id_bias = utils::strdup(arg[iarg+1]);
       iarg += 2;
     } else if (strcmp(arg[iarg],"dof") == 0) {
       if (iarg+2 > narg)
diff --git a/src/BODY/compute_temp_body.cpp b/src/BODY/compute_temp_body.cpp
index 730a857aec..fb16723b23 100644
--- a/src/BODY/compute_temp_body.cpp
+++ b/src/BODY/compute_temp_body.cpp
@@ -56,9 +56,7 @@ ComputeTempBody::ComputeTempBody(LAMMPS *lmp, int narg, char **arg) :
       if (iarg+2 > narg)
         error->all(FLERR,"Illegal compute temp/body command");
       tempbias = 1;
-      int n = strlen(arg[iarg+1]) + 1;
-      id_bias = new char[n];
-      strcpy(id_bias,arg[iarg+1]);
+      id_bias = utils::strdup(arg[iarg+1]);
       iarg += 2;
     } else if (strcmp(arg[iarg],"dof") == 0) {
       if (iarg+2 > narg)
diff --git a/src/GPU/fix_npt_gpu.cpp b/src/GPU/fix_npt_gpu.cpp
index 2ba0be29e0..073d5dc6c1 100644
--- a/src/GPU/fix_npt_gpu.cpp
+++ b/src/GPU/fix_npt_gpu.cpp
@@ -25,44 +25,24 @@ FixNPTGPU::FixNPTGPU(LAMMPS *lmp, int narg, char **arg) :
   FixNHGPU(lmp, narg, arg)
 {
   if (!tstat_flag)
-    error->all(FLERR,"Temperature control must be used with fix npt/omp");
+    error->all(FLERR,"Temperature control must be used with fix npt/gpu");
   if (!pstat_flag)
-    error->all(FLERR,"Pressure control must be used with fix npt/omp");
+    error->all(FLERR,"Pressure control must be used with fix npt/gpu");
 
   // create a new compute temp style
   // id = fix-ID + temp
   // compute group = all since pressure is always global (group all)
   // and thus its KE/temperature contribution should use group all
 
-  int n = strlen(id) + 6;
-  id_temp = new char[n];
-  strcpy(id_temp,id);
-  strcat(id_temp,"_temp");
-
-  char **newarg = new char*[3];
-  newarg[0] = id_temp;
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "temp";
-
-  modify->add_compute(3,newarg);
-  delete [] newarg;
+  id_temp = utils::strdup(std::string(id)+"_temp");
+  modify->add_compute(id_temp+" all temp");
   tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
   // pass id_temp as 4th arg to pressure constructor
 
-  n = strlen(id) + 7;
-  id_press = new char[n];
-  strcpy(id_press,id);
-  strcat(id_press,"_press");
-
-  newarg = new char*[4];
-  newarg[0] = id_press;
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "pressure";
-  newarg[3] = id_temp;
-  modify->add_compute(4,newarg);
-  delete [] newarg;
+  id_press = utils::strdup(std::string(id)+"_press");
+  modify->add_compute(std::string(id_press)+" all pressure "+id_temp);
   pcomputeflag = 1;
 }
diff --git a/src/GPU/fix_nvt_gpu.cpp b/src/GPU/fix_nvt_gpu.cpp
index 7d7826b6bf..6858c26497 100644
--- a/src/GPU/fix_nvt_gpu.cpp
+++ b/src/GPU/fix_nvt_gpu.cpp
@@ -26,25 +26,14 @@ FixNVTGPU::FixNVTGPU(LAMMPS *lmp, int narg, char **arg) :
   FixNHGPU(lmp, narg, arg)
 {
   if (!tstat_flag)
-    error->all(FLERR,"Temperature control must be used with fix nvt");
+    error->all(FLERR,"Temperature control must be used with fix nvt/gpu");
   if (pstat_flag)
-    error->all(FLERR,"Pressure control can not be used with fix nvt");
+    error->all(FLERR,"Pressure control can not be used with fix nvt/gpu");
 
   // create a new compute temp style
   // id = fix-ID + temp
 
-  int n = strlen(id) + 6;
-  id_temp = new char[n];
-  strcpy(id_temp,id);
-  strcat(id_temp,"_temp");
-
-  char **newarg = new char*[3];
-  newarg[0] = id_temp;
-  newarg[1] = group->names[igroup];
-  newarg[2] = (char *) "temp";
-
-  modify->add_compute(3,newarg);
-  delete [] newarg;
+  id_temp = utils::strdup(std::string(id)+"_temp");
+  modify->add_compute(fmt::format("{} {} temp",id_temp,group->names[igroup]));
   tcomputeflag = 1;
 }
-
diff --git a/src/USER-OMP/fix_npt_omp.cpp b/src/USER-OMP/fix_npt_omp.cpp
index f3f08c15c2..54328803f4 100644
--- a/src/USER-OMP/fix_npt_omp.cpp
+++ b/src/USER-OMP/fix_npt_omp.cpp
@@ -34,35 +34,16 @@ FixNPTOMP::FixNPTOMP(LAMMPS *lmp, int narg, char **arg) :
   // compute group = all since pressure is always global (group all)
   // and thus its KE/temperature contribution should use group all
 
-  int n = strlen(id) + 6;
-  id_temp = new char[n];
-  strcpy(id_temp,id);
-  strcat(id_temp,"_temp");
 
-  char **newarg = new char*[3];
-  newarg[0] = id_temp;
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "temp";
-
-  modify->add_compute(3,newarg);
-  delete [] newarg;
+  id_temp = utils::strdup(std::string(id)+"_temp");
+  modify->add_compute(std::string(id_temp)+" all temp");
   tcomputeflag = 1;
 
   // create a new compute pressure style
   // id = fix-ID + press, compute group = all
   // pass id_temp as 4th arg to pressure constructor
 
-  n = strlen(id) + 7;
-  id_press = new char[n];
-  strcpy(id_press,id);
-  strcat(id_press,"_press");
-
-  newarg = new char*[4];
-  newarg[0] = id_press;
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "pressure";
-  newarg[3] = id_temp;
-  modify->add_compute(4,newarg);
-  delete [] newarg;
+  id_press = utils::strdup(std::string(id)+"_press");
+  modify->add_compute(std::string(id_press)+" all pressure "+id_temp);
   pcomputeflag = 1;
 }
diff --git a/src/USER-OMP/fix_nvt_omp.cpp b/src/USER-OMP/fix_nvt_omp.cpp
index bfa2dcbe49..127876b4e8 100644
--- a/src/USER-OMP/fix_nvt_omp.cpp
+++ b/src/USER-OMP/fix_nvt_omp.cpp
@@ -33,17 +33,7 @@ FixNVTOMP::FixNVTOMP(LAMMPS *lmp, int narg, char **arg) :
   // create a new compute temp style
   // id = fix-ID + temp
 
-  int n = strlen(id) + 6;
-  id_temp = new char[n];
-  strcpy(id_temp,id);
-  strcat(id_temp,"_temp");
-
-  char **newarg = new char*[3];
-  newarg[0] = id_temp;
-  newarg[1] = group->names[igroup];
-  newarg[2] = (char *) "temp";
-
-  modify->add_compute(3,newarg);
-  delete [] newarg;
+  id_temp = utils::strdup(std::string(id)+"_temp");
+  modify->add_compute(fmt::format("{} {} temp",id_temp,group->names[igroup]));
   tcomputeflag = 1;
 }