diff --git a/src/compute_chunk_atom.cpp b/src/compute_chunk_atom.cpp
index 34bd855879..f7e2db69b9 100644
--- a/src/compute_chunk_atom.cpp
+++ b/src/compute_chunk_atom.cpp
@@ -582,8 +582,12 @@ void ComputeChunkAtom::init()
   // fixstore initializes all values to 0.0
 
   if ((idsflag == ONCE || lockcount) && !fixstore) {
-    modify->add_fix(fmt::format("{}_COMPUTE_STORE {} STORE peratom 1 1",
-                                id,group->names[igroup]));
+    std::string cmd = id + std::string("_COMPUTE_STORE");
+    id_fix = new char[cmd.size()+1];
+    strcpy(id_fix,cmd.c_str());
+
+    cmd += fmt::format(" {} STORE peratom 1 1", group->names[igroup]);
+    modify->add_fix(cmd);
     fixstore = (FixStore *) modify->fix[modify->nfix-1];
   }
 
diff --git a/src/compute_displace_atom.cpp b/src/compute_displace_atom.cpp
index 9a82924acb..b20dd3bec3 100644
--- a/src/compute_displace_atom.cpp
+++ b/src/compute_displace_atom.cpp
@@ -73,8 +73,12 @@ ComputeDisplaceAtom::ComputeDisplaceAtom(LAMMPS *lmp, int narg, char **arg) :
   // create a new fix STORE style
   // id = compute-ID + COMPUTE_STORE, fix group = compute group
 
-  modify->add_fix(fmt::format("{}_COMPUTE_STORE {} STORE peratom 1 3",
-                              id,group->names[igroup]));
+  std::string cmd = id + std::string("_COMPUTE_STORE");
+  id_fix = new char[cmd.size()+1];
+  strcpy(id_fix,cmd.c_str());
+
+  cmd += fmt::format(" {} STORE peratom 1 3", group->names[igroup]);
+  modify->add_fix(cmd);
   fix = (FixStore *) modify->fix[modify->nfix-1];
 
   // calculate xu,yu,zu for fix store array
diff --git a/src/fix_numdiff.cpp b/src/fix_numdiff.cpp
index 0fc5b4ada0..a4ac86e0c5 100644
--- a/src/fix_numdiff.cpp
+++ b/src/fix_numdiff.cpp
@@ -55,17 +55,12 @@ FixNumDiff::FixNumDiff(LAMMPS *lmp, int narg, char **arg) :
   if (nevery <= 0 || delta <= 0.0)
     error->all(FLERR,"Illegal fix numdiff command");
 
-  int n = strlen(id) + 6;
-  id_pe = new char[n];
-  strcpy(id_pe,id);
-  strcat(id_pe,"_pe");
+  std::string cmd = id + std::string("_pe");
+  id_pe = new char[cmd.size()+1];
+  strcpy(id_pe,cmd.c_str());
 
-  char **newarg = new char*[3];
-  newarg[0] = id_pe;
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "pe";
-  modify->add_compute(3,newarg);
-  delete [] newarg;
+  cmd += " all pe";
+  modify->add_compute(cmd);
 
   maxatom = 0;
 
diff --git a/src/fix_press_berendsen.cpp b/src/fix_press_berendsen.cpp
index 184f02c440..db6d56799a 100644
--- a/src/fix_press_berendsen.cpp
+++ b/src/fix_press_berendsen.cpp
@@ -14,6 +14,7 @@
 #include "fix_press_berendsen.h"
 #include <cstring>
 #include <cmath>
+#include <string>
 #include "atom.h"
 #include "force.h"
 #include "comm.h"
@@ -217,35 +218,24 @@ FixPressBerendsen::FixPressBerendsen(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");
+  std::string tcmd = id + std::string("_temp");
+  id_temp = new char[tcmd.size()+1];
+  strcpy(id_temp,tcmd.c_str());
 
-  char **newarg = new char*[3];
-  newarg[0] = id_temp;
-  newarg[1] = (char *) "all";
-  newarg[2] = (char *) "temp";
-  modify->add_compute(3,newarg);
-  delete [] newarg;
+  tcmd += " all temp";
+  modify->add_compute(tcmd);
   tflag = 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");
+  std::string pcmd = id + std::string("_press");
+  id_press = new char[pcmd.size()+1];
+  strcpy(id_press,pcmd.c_str());
 
-  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;
+  pcmd += " all pressure " + std::string(id_temp);
+  modify->add_compute(pcmd);
   pflag = 1;
 
   nrigid = 0;
diff --git a/src/fix_temp_berendsen.cpp b/src/fix_temp_berendsen.cpp
index be8922be4e..2f687aeecf 100644
--- a/src/fix_temp_berendsen.cpp
+++ b/src/fix_temp_berendsen.cpp
@@ -13,6 +13,7 @@
 
 #include "fix_temp_berendsen.h"
 #include <cstring>
+#include <string>
 #include <cmath>
 #include "atom.h"
 #include "force.h"
@@ -70,17 +71,12 @@ FixTempBerendsen::FixTempBerendsen(LAMMPS *lmp, int narg, char **arg) :
   // create a new compute temp style
   // id = fix-ID + temp, compute group = fix group
 
-  int n = strlen(id) + 6;
-  id_temp = new char[n];
-  strcpy(id_temp,id);
-  strcat(id_temp,"_temp");
+  std::string cmd = id + std::string("_temp");
+  id_temp = new char[cmd.size()+1];
+  strcpy(id_temp,cmd.c_str());
 
-  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;
+  cmd += group->names[igroup] + std::string(" temp");
+  modify->add_compute(cmd);
   tflag = 1;
 
   energy = 0;
diff --git a/src/fix_temp_csld.cpp b/src/fix_temp_csld.cpp
index f827c88f51..715d9a8692 100644
--- a/src/fix_temp_csld.cpp
+++ b/src/fix_temp_csld.cpp
@@ -17,6 +17,7 @@
 
 #include "fix_temp_csld.h"
 #include <cstring>
+#include <string>
 #include <cmath>
 #include "atom.h"
 #include "force.h"
@@ -79,17 +80,12 @@ FixTempCSLD::FixTempCSLD(LAMMPS *lmp, int narg, char **arg) :
   // create a new compute temp style
   // id = fix-ID + temp, compute group = fix group
 
-  int n = strlen(id) + 6;
-  id_temp = new char[n];
-  strcpy(id_temp,id);
-  strcat(id_temp,"_temp");
+  std::string cmd = id + std::string("_temp");
+  id_temp = new char[cmd.size()+1];
+  strcpy(id_temp,cmd.c_str());
 
-  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;
+  cmd += group->names[igroup] + std::string(" temp");
+  modify->add_compute(cmd);
   tflag = 1;
 
   vhold = NULL;
diff --git a/src/fix_temp_csvr.cpp b/src/fix_temp_csvr.cpp
index 55cbb60407..aabdcf2bc3 100644
--- a/src/fix_temp_csvr.cpp
+++ b/src/fix_temp_csvr.cpp
@@ -20,6 +20,7 @@
 #include <mpi.h>
 #include <cstring>
 #include <cmath>
+#include <string>
 #include "atom.h"
 #include "force.h"
 #include "comm.h"
@@ -156,17 +157,12 @@ FixTempCSVR::FixTempCSVR(LAMMPS *lmp, int narg, char **arg) :
   // create a new compute temp style
   // id = fix-ID + temp, compute group = fix group
 
-  int n = strlen(id) + 6;
-  id_temp = new char[n];
-  strcpy(id_temp,id);
-  strcat(id_temp,"_temp");
+  std::string cmd = id + std::string("_temp");
+  id_temp = new char[cmd.size()+1];
+  strcpy(id_temp,cmd.c_str());
 
-  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;
+  cmd += group->names[igroup] + std::string(" temp");
+  modify->add_compute(cmd);
   tflag = 1;
 
   nmax = -1;
diff --git a/src/fix_temp_rescale.cpp b/src/fix_temp_rescale.cpp
index a9d605d5ba..f25d1408cc 100644
--- a/src/fix_temp_rescale.cpp
+++ b/src/fix_temp_rescale.cpp
@@ -13,6 +13,7 @@
 
 #include "fix_temp_rescale.h"
 #include <cstring>
+#include <string>
 #include <cmath>
 #include "atom.h"
 #include "force.h"
@@ -66,17 +67,12 @@ FixTempRescale::FixTempRescale(LAMMPS *lmp, int narg, char **arg) :
   // create a new compute temp
   // id = fix-ID + temp, compute group = fix group
 
-  int n = strlen(id) + 6;
-  id_temp = new char[n];
-  strcpy(id_temp,id);
-  strcat(id_temp,"_temp");
+  std::string cmd = id + std::string("_temp");
+  id_temp = new char[cmd.size()+1];
+  strcpy(id_temp,cmd.c_str());
 
-  char **newarg = new char*[6];
-  newarg[0] = id_temp;
-  newarg[1] = group->names[igroup];
-  newarg[2] = (char *) "temp";
-  modify->add_compute(3,newarg);
-  delete [] newarg;
+  cmd += group->names[igroup] + std::string(" temp");
+  modify->add_compute(cmd);
   tflag = 1;
 
   energy = 0.0;