[h2root] occassional memory corruption issue stems from substring replacement

by adding a space, we create an extra char that will be substituted by c, rather than appending to the string

Author: ferdymercury

main/src/h2root.cxx

@@ -312,7 +312,11 @@ int main(int argc, char **argv)
 
    int lun = 10;
 #ifndef WIN32
-   hropen(lun,PASSCHAR("example"),PASSCHAR(file_in),PASSCHAR("px"),record_size,ier,7,strlen(file_in),2);
+   // "px" is a string being changed to "pxc" in the fortran side; since it's a temporary on C's side,
+   // we need a buffer of at least 3 chars on Cs side, too. Predefine it as a extra variable "px " since that way
+   // the space will be replaced by 'c' on the preallocated memory, instead of appending a new char (new memory) to "px".
+   auto opt = PASSCHAR("px ");
+   hropen(lun,PASSCHAR("example"),PASSCHAR(file_in),opt,record_size,ier,7,strlen(file_in),2);
 #else
    hropen(lun,PASSCHAR("example"),PASSCHAR(file_in),PASSCHAR("px"),record_size,ier);
 #endif