pike.git/ src/ svalue.h

2014-06-26

2014-06-26 18:14:58 by Henrik Grubbström (Grubba) <grubba@grubba.org>

• bf3c855c290c626d1df11bf9b6e718952633edef (49 lines) (+40/-9) ^{[ Show | Annotate ]}
  Branch: 8.0

Build: Support compilers with union aliasing problems.

There are apparently compilers that don't understand that the
fields in unions overlap, and overcache overwritten fieldvalues.

Also restores support for compilers without support for static union init.

90:   /* Note: At least multisets overlays the type field and uses the top 4    * bits in it internally. */    + #if !defined(HAVE_UNION_INIT) && !defined(NO_COMBINED_TYPE_SUBTYPE) + /* We can't use the tu union in this case, since we need to +  * support static initialization of svalues. +  */ + #define NO_COMBINED_TYPE_SUBTYPE + #endif +    /**    */   struct svalue   { -  + #ifndef NO_COMBINED_TYPE_SUBTYPE    union {    struct {    unsigned short type; /**< the data type, see PIKE_T_... */
111:   #endif   #endif    } tu; + #else /* NO_COMBINED_TYPE_SUBTYPE */ +  /* Syntax-compatible with the above, but only structs, +  * and thus no combined type_subtype field. +  */ +  struct { +  struct { +  unsigned short type; /**< the data type, see PIKE_T_... */ +  unsigned short subtype; /**< used to store the zero type, among others */ +  } t; +  } tu; + #endif /* NO_COMBINED_TYPE_SUBTYPE */    union anything u; /**< contains the value */   };    -  + #define TYPEOF(SVAL) ((SVAL).tu.t.type) + #define SUBTYPEOF(SVAL) ((SVAL).tu.t.subtype) +  + #define SET_SVAL_TYPE(SVAL, TYPE) (TYPEOF(SVAL) = (TYPE)) + #define SET_SVAL_SUBTYPE(SVAL, TYPE) (SUBTYPEOF(SVAL) = (TYPE)) +  + #ifdef NO_COMBINED_TYPE_SUBTYPE + /* Some compilers have aliasing problems with unions, +  * so skip the optimization of setting both fields +  * with one write with them. +  */ + #define SET_SVAL_TYPE_SUBTYPE(SVAL, TYPE, SUBTYPE) \ +  ((TYPEOF(SVAL) = (TYPE)), \ +  (SUBTYPEOF(SVAL) = (SUBTYPE))) + #else   #if PIKE_BYTEORDER == 1234   #define TYPE_SUBTYPE(X,Y) ((X)|((Y)<<16))   #else   #define TYPE_SUBTYPE(X,Y) ((Y)|((X)<<16))   #endif    - #define TYPEOF(SVAL) ((SVAL).tu.t.type) - #define SUBTYPEOF(SVAL) ((SVAL).tu.t.subtype) +    #define SET_SVAL_TYPE_SUBTYPE(SVAL, TYPE, SUBTYPE) \    ((SVAL).tu.type_subtype = TYPE_SUBTYPE(TYPE,SUBTYPE)) -  + #endif    - #define SET_SVAL_TYPE(SVAL, TYPE) (TYPEOF(SVAL) = (TYPE)) - #define SET_SVAL_SUBTYPE(SVAL, TYPE) (SUBTYPEOF(SVAL) = (TYPE)) -  +    #define SET_SVAL(SVAL, TYPE, SUBTYPE, FIELD, EXPR) do { \    /* Set the type afterwards to avoid a clobbered \    * svalue in case EXPR throws. */ \    struct svalue * __sv_ptr = &( SVAL ); \    __sv_ptr->u.FIELD = (EXPR); \ -  __sv_ptr->tu.type_subtype = TYPE_SUBTYPE(TYPE,SUBTYPE);\ +  SET_SVAL_TYPE_SUBTYPE(*__sv_ptr, TYPE, SUBTYPE); \    } while(0)      /*
913:   #define SVALUE_INIT_INT(VAL) {{{T_INT, NUMBER_NUMBER}}, {VAL}}   #define SVALUE_INIT_FREE {{{PIKE_T_FREE, NUMBER_NUMBER}}, {0}}   #else - #define SVALUE_INIT(TYPE, SUBTYPE, VAL) {TYPE, SUBTYPE, VAL} - #define SVALUE_INIT_INT(VAL) {T_INT, NUMBER_NUMBER, VAL} - #define SVALUE_INIT_FREE {PIKE_T_FREE, NUMBER_NUMBER, VAL} + #define SVALUE_INIT(TYPE, SUBTYPE, VAL) {{{TYPE, SUBTYPE}}} + #define SVALUE_INIT_INT(VAL) {{{T_INT, NUMBER_NUMBER}}} + #define SVALUE_INIT_FREE {{{PIKE_T_FREE, NUMBER_NUMBER}}}   #endif      #endif /* !SVALUE_H */