On Mon, Apr 28, 2014 at 1:20 PM, Thomas Schmitt <scdbac...@gmx.net> wrote:
> Hi, > > > I really need a disassembly and to be able to probe the runtime > It's the job of a C union to provide a common hull around objects > of different size. One may dispute whether using union is a good > idea (like overloading in the OO paradigm). But unions are part of C > since K&R and they are supposed to be safe. > > http://www.gnu.org/software/gnu-c-manual/gnu-c-manual.html#Size-of-Unions No, it's plain wrong. Unions are fine, if used properly. You aren't using them properly. Let me show you how by a more extreme example: #include <stdlib.h> struct small { int a; }; struct big { int b[1024*1024]; }; union both { struct small imSmall; struct big imBig; }; void copy(union both* b, void* data) { *b = *(union both*)data; //copies 4MB of data. } void main() { struct small smallThing; union both* bothThings = malloc(sizeof(union both)); copy(bothThings, &smallThing); // NOT OK. struct small cannot NOT be converted to union both. } figgles@ghost:~$ ./big Segmentation fault ---- The problem is that union can convert to a member (by accessing the field), but a member CANNOT convert to a union. add_worker() takes a member and tries to convert it to a union. This is WRONG. Period.
