improve error handling to make coverity scan happy

tools/msi2lmp/src/ReadCarFile.c

@@ -132,7 +132,10 @@ void ReadCarFile(void)
       no_molecules++;
 
   /* Allocate space to keep track of the number of atoms within a molecule */
-
+  if (no_molecules < 1) {
+    fprintf(stderr, "No molecules in system");
+    exit(32);
+  }
   no_atoms = (int *) calloc(no_molecules,sizeof(int));
   if ( no_atoms == NULL ) {
     printf("Could not allocate memory for no_atoms\n");

tools/msi2lmp/src/SearchAndFill.c

@@ -12,6 +12,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <ctype.h>
+#include <errno.h>
 
 #if defined(_WIN32)
 #define strdup(x) _strdup(x)
@@ -91,6 +92,10 @@ void SearchAndFill(struct FrcFieldItem *item)
   }
 
   file_pos = ftell(FrcF);
+  if (file_pos < 0) {
+    fprintf(stderr, "Could not obtain file stream position: ", strerror(errno));
+    exit(2);
+  }
 
   /* Count the number of lines until next item is found */
 
@@ -110,7 +115,10 @@ void SearchAndFill(struct FrcFieldItem *item)
 
   /* Read lines until keyword is found */
 
-  fseek(FrcF,file_pos,SEEK_SET);
+  if (fseek(FrcF,file_pos,SEEK_SET) < 0) {
+    fprintf(stderr, "Resetting file stream failed: ", strerror(errno));
+    exit(2);
+  }
   strcpy(line,"empty");
 
   /* Read lines until data starts (when !--- is found) */