message: fix an error reported by static analysis
diff: @@ -138,7 +138,7 @@ public:
  int REDEFINE =
  0; // 1: delete and redefine variable definitions at each step to
  // test adios_delete_vardefs()
  - char *FILENAME = nullptr;
  + std::string FILENAME;
  /* Variables to write */
  int *a2 = nullptr;
  @@ -242,11 +242,9 @@ public:
  NBLOCKS = p.nblocks;
  NSTEPS = p.nsteps;
  REDEFINE = redefineVars;
  - std::string fn = "manyVars." + std::to_string(NVARS) + "_" +
  - std::to_string(NBLOCKS) + "_" +
  - std::to_string(NSTEPS) + "_" +
  - (REDEFINE ? "redefine" : "") + ".bp";
  - FILENAME = const_cast<char *>(fn.c_str());
  + FILENAME = "manyVars." + std::to_string(NVARS) + "_" +
  + std::to_string(NBLOCKS) + "_" + std::to_string(NSTEPS) +
  + "_" + (REDEFINE ? "redefine" : "") + ".bp";
  alloc_vars();
  adios2_adios *adiosH =
  @@ -261,7 +259,7 @@ public:
  NSTEPS);
  }
  - engineW = adios2_open(ioW, FILENAME, adios2_mode_write);
  + engineW = adios2_open(ioW, FILENAME.c_str(), adios2_mode_write);
  err = 0;
  for (i = 0; i < NSTEPS; i++)
  @@ -316,14 +314,15 @@ public:
  double tb, te;
  size_t count[2] = {ldim1, ldim2};
  - log("Write step %d to %s\n", step, FILENAME);
  + log("Write step %d to %s\n", step, FILENAME.c_str());
  tb = MPI_Wtime();
  adios2_begin_step(engineW, adios2_step_mode_append, 0.0);
  for (block = 0; block < NBLOCKS; block++)
  {
  v = VALUE(rank, step, block);
  - log(" Write block %d, value %d to %s\n", block, v, FILENAME);
  + log(" Write block %d, value %d to %s\n", block, v,
  + FILENAME.c_str());
  set_vars(step, block);
  size_t start[2] = {offs1, offs2};
  for (i = 0; i < NVARS; i++)
  @@ -366,18 +365,19 @@ public:
  reset_readvars();
  - log("Read and check data in %s\n", FILENAME);
  - adios2_engine *engineR = adios2_open(ioR, FILENAME, adios2_mode_read);
  + log("Read and check data in %s\n", FILENAME.c_str());
  + adios2_engine *engineR =
  + adios2_open(ioR, FILENAME.c_str(), adios2_mode_read);
  if (engineR == NULL)
  {
  - printE("Error at opening file %s for reading\n", FILENAME);
  + printE("Error at opening file %s for reading\n", FILENAME.c_str());
  return 1;
  }
  adios2_step_status status =
  adios2_begin_step(engineR, adios2_step_mode_next_available, 0.0);
  - log(" Check variable definitions... %s\n", FILENAME);
  + log(" Check variable definitions... %s\n", FILENAME.c_str());
  tb = MPI_Wtime();
  for (i = 0; i < NVARS; i++)
  {
  