Implemented optional C++ exceptions in Error class

These can be activated using the -DLAMMPS_EXCEPTIONS compiler flag.
It has no effect for regular execution. However, while using
it as a library, any issued command will capture the exception
and save its error message. This can be queried using the
lammps_has_error() and lammps_get_last_error_message() methods.

The Python wrapper checks these in order to rethrow these errors
as Python exceptions. See issue #146.

(cherry picked from commit 6c154bb0b67a13d38968bc42d31013b97f87db75)

python/lammps.py

@@ -150,6 +150,11 @@ class lammps(object):
     if cmd: cmd = cmd.encode()
     self.lib.lammps_command(self.lmp,cmd)
 
+    if self.lib.lammps_has_error(self.lmp):
+      sb = create_string_buffer(100)
+      self.lib.lammps_get_last_error_message(self.lmp, sb, 100)
+      raise Exception(sb.value.decode().strip())
+
   def extract_global(self,name,type):
     if name: name = name.encode()
     if type == 0:

src/error.cpp

@@ -13,6 +13,7 @@
 
 #include <mpi.h>
 #include <stdlib.h>
+#include <string.h>
 #include "error.h"
 #include "universe.h"
 #include "output.h"
@@ -21,7 +22,7 @@ using namespace LAMMPS_NS;
 
 /* ---------------------------------------------------------------------- */
 
-Error::Error(LAMMPS *lmp) : Pointers(lmp) {}
+Error::Error(LAMMPS *lmp) : Pointers(lmp), last_error_message(NULL) {}
 
 /* ----------------------------------------------------------------------
    called by all procs in universe
@@ -47,8 +48,14 @@ void Error::universe_all(const char *file, int line, const char *str)
   }
   if (universe->ulogfile) fclose(universe->ulogfile);
 
+#ifdef LAMMPS_EXCEPTIONS
+  char msg[100];
+  sprintf(msg, "ERROR: %s (%s:%d)\n", str, file, line);
+  throw LAMMPSException(msg);
+#else
   MPI_Finalize();
   exit(1);
+#endif
 }
 
 /* ----------------------------------------------------------------------
@@ -61,7 +68,14 @@ void Error::universe_one(const char *file, int line, const char *str)
   if (universe->uscreen)
     fprintf(universe->uscreen,"ERROR on proc %d: %s (%s:%d)\n",
             universe->me,str,file,line);
+
+#ifdef LAMMPS_EXCEPTIONS
+  char msg[100];
+  sprintf(msg, "ERROR: %s (%s:%d)\n", str, file, line);
+  throw LAMMPSAbortException(msg, universe->uworld);
+#else
   MPI_Abort(universe->uworld,1);
+#endif
 }
 
 /* ----------------------------------------------------------------------
@@ -95,6 +109,16 @@ void Error::all(const char *file, int line, const char *str)
     if (logfile) fprintf(logfile,"ERROR: %s (%s:%d)\n",str,file,line);
   }
 
+#ifdef LAMMPS_EXCEPTIONS
+  char msg[100];
+  sprintf(msg, "ERROR: %s (%s:%d)\n", str, file, line);
+
+  if (universe->nworlds > 1) {
+    throw LAMMPSAbortException(msg, universe->uworld);
+  }
+
+  throw LAMMPSException(msg);
+#else
   if (output) delete output;
   if (screen && screen != stdout) fclose(screen);
   if (logfile) fclose(logfile);
@@ -102,6 +126,7 @@ void Error::all(const char *file, int line, const char *str)
   if (universe->nworlds > 1) MPI_Abort(universe->uworld,1);
   MPI_Finalize();
   exit(1);
+#endif
 }
 
 /* ----------------------------------------------------------------------
@@ -121,7 +146,14 @@ void Error::one(const char *file, int line, const char *str)
     if (universe->uscreen)
       fprintf(universe->uscreen,"ERROR on proc %d: %s (%s:%d)\n",
               universe->me,str,file,line);
+
+#ifdef LAMMPS_EXCEPTIONS
+  char msg[100];
+  sprintf(msg, "ERROR on proc %d: %s (%s:%d)\n", me, str, file, line);
+  throw LAMMPSAbortException(msg, world);
+#else
   MPI_Abort(world,1);
+#endif
 }
 
 /* ----------------------------------------------------------------------
@@ -165,3 +197,31 @@ void Error::done(int status)
   MPI_Finalize();
   exit(status);
 }
+
+/* ----------------------------------------------------------------------
+   return the last error message reported by LAMMPS (only used if
+   compiled with -DLAMMPS_EXCEPTIONS)
+------------------------------------------------------------------------- */
+
+char * Error::get_last_error() const
+{
+  return last_error_message;
+}
+
+
+/* ----------------------------------------------------------------------
+   set the last error message (only used if compiled with
+   -DLAMMPS_EXCEPTIONS)
+------------------------------------------------------------------------- */
+
+void Error::set_last_error(const char * msg)
+{
+  delete [] last_error_message;
+
+  if(msg) {
+    last_error_message = new char[strlen(msg)+1];
+    strcpy(last_error_message, msg);
+  } else {
+    last_error_message = NULL;
+  }
+}

src/error.h

@@ -15,10 +15,41 @@
 #define LMP_ERROR_H
 
 #include "pointers.h"
+#include <string>
+#include <exception>
 
 namespace LAMMPS_NS {
 
+class LAMMPSException : public std::exception
+{
+public:
+  std::string message;
+
+  LAMMPSException(std::string msg) : message(msg) {
+  }
+
+  ~LAMMPSException() throw() {
+  }
+
+  virtual const char * what() const throw() {
+    return message.c_str();
+  }
+};
+
+class LAMMPSAbortException : public LAMMPSException {
+public:
+  MPI_Comm universe;
+
+  LAMMPSAbortException(std::string msg, MPI_Comm universe) :
+    LAMMPSException(msg),
+    universe(universe)
+  {
+  }
+};
+
 class Error : protected Pointers {
+  char * last_error_message;
+
  public:
   Error(class LAMMPS *);
 
@@ -31,6 +62,9 @@ class Error : protected Pointers {
   void warning(const char *, int, const char *, int = 1);
   void message(const char *, int, const char *, int = 1);
   void done(int = 0); // 1 would be fully backwards compatible
+
+  char * get_last_error() const;
+  void   set_last_error(const char * msg);
 };
 
 }

src/library.cpp

@@ -108,8 +108,15 @@ void lammps_file(void *ptr, char *str)
 
 char *lammps_command(void *ptr, char *str)
 {
-  LAMMPS *lmp = (LAMMPS *) ptr;
+  LAMMPS *  lmp = (LAMMPS *) ptr;
-  return lmp->input->one(str);
+  Error * error = lmp->error;
+
+  try {
+    return lmp->input->one(str);
+  } catch(LAMMPSException & e) {
+    error->set_last_error(e.message.c_str());
+    return NULL;
+  }
 }
 
 /* ----------------------------------------------------------------------
@@ -593,3 +600,29 @@ void lammps_scatter_atoms(void *ptr, char *name,
     }
   }
 }
+
+/* ----------------------------------------------------------------------
+   Check if a new error message
+------------------------------------------------------------------------- */
+
+int lammps_has_error(void *ptr) {
+  LAMMPS *  lmp = (LAMMPS *) ptr;
+  Error * error = lmp->error;
+  return error->get_last_error() ? 1 : 0;
+}
+
+/* ----------------------------------------------------------------------
+   Copy the last error message of LAMMPS into a character buffer
+------------------------------------------------------------------------- */
+
+int lammps_get_last_error_message(void *ptr, char * buffer, int buffer_size) {
+  LAMMPS *  lmp = (LAMMPS *) ptr;
+  Error * error = lmp->error;
+
+  if(error->get_last_error()) {
+    strncpy(buffer, error->get_last_error(), buffer_size-1);
+    error->set_last_error(NULL);
+    return 1;
+  }
+  return 0;
+}

src/library.h

@@ -45,6 +45,9 @@ int lammps_get_natoms(void *);
 void lammps_gather_atoms(void *, char *, int, int, void *);
 void lammps_scatter_atoms(void *, char *, int, int, void *);
 
+int lammps_has_error(void *);
+int lammps_get_last_error_message(void *, char *, int);
+
 #ifdef __cplusplus
 }
 #endif

src/main.cpp

@@ -14,7 +14,9 @@
 #include <mpi.h>
 #include "lammps.h"
 #include "input.h"
+#include "error.h"
 #include <stdio.h>
+#include <stdlib.h>
 
 using namespace LAMMPS_NS;
 
@@ -26,11 +28,22 @@ int main(int argc, char **argv)
 {
   MPI_Init(&argc,&argv);
 
+#ifdef LAMMPS_EXCEPTIONS
+  try {
+    LAMMPS *lammps = new LAMMPS(argc,argv,MPI_COMM_WORLD);
+    lammps->input->file();
+    delete lammps;
+  } catch(LAMMPSAbortException & ae) {
+    MPI_Abort(ae.universe, 1);
+  } catch(LAMMPSException & e) {
+    MPI_Finalize();
+    exit(1);
+  }
+#else
   LAMMPS *lammps = new LAMMPS(argc,argv,MPI_COMM_WORLD);
-
   lammps->input->file();
   delete lammps;
-
+#endif
   MPI_Barrier(MPI_COMM_WORLD);
   MPI_Finalize();
 }