Re: Not able to use %union?
Christian Schoenebeck <[email protected]>
| Newsgroups | gmane.comp.parsers.bison.general |
|---|---|
| Message-ID | <1994237.YnnV8muOGF@silver> |
On Sonntag, 17. Februar 2019 21:37:26 CET Peng Yu wrote: > Because I want to use the previously allocated memory, I don't want to > call "rs_init(&yylval->str)" in any action. So YYSTYPE must be a > struct instead of a union. Is it a good practice to use struct instead > of union? Yes, it is. The only advantage by using a union as a type is that you save some tiny amount of memory, but a union is also less safe and harder to debug. So personally I would barely ever use union as fundamental type with Bison. > Since %union cannot be used in this case, how to deal with this > scenario in bison? Thanks. There is actually no difference in usage, since the Bison generated parser code will access the fields in the same way: simply by using the union/struct member names you defined (e.g val.num, val.str in your example). So the actual difference between struct or union is handled by the C/C++ compiler, not by Bison. Any reason that you don't want to use C++ and e.g. std::string instead of your pure C and garbage collector solution? Best regards, Christian Schoenebeck _______________________________________________ [email protected] https://lists.gnu.org/mailman/listinfo/help-bison