It is a minor issue. In the Standard, the description for int MPI_T_pvar_get_info(..., int *readonly, int *continuous, int *atomic) says: Upon return, the argument readonly is set to zero if the variable can be written or reset by the user. It is set to *one* if the variable can only be read. (Same thing happens to continuous and atomic.) The description mandates an implementation must return 1 as TRUE, which does not follow C's convention. Other parts of MPI use true/false instead of 1/0 in description. Section 2.6.3 make it clear that true means non-zero. Thanks. --Junchao Zhang