String evaluation bug

metadata:
  file_name:  { type: array, subtype: char, size: 32 }
plugins:
  decl_hdf5:
    - file: ${file_name}.h5
      ...

sprintf(file_name, "%s", "example");
PDI_expose("file_name", file_name, PDI_OUT);

The expression ${file_name}.h5 evaluates to example not example.h5. The reason is that, the sprintf adds \0 char at the end of const char* string and the Expression puts to evaluated string: example\0.h5. Then the H5Fopen reads it as a const char* string (stops at \0).