src/pmc/eval.pmc: Walk the fixups, locate globals and nullify the Sub PMC

[jkeenan]

This ticket moves into the Trac system an issue previously discussed in the RT system as  RT #46683.

139 =item C<opcode_t *invoke(void *next)>
140 
141 Invokes the first subroutine in the eval code.
142 
143 =cut
144 
145 */
146 
147     VTABLE opcode_t *invoke(void *next) {
148         PMC *sub = SELF.get_pmc_keyed_int(0);
149         return VTABLE_invoke(INTERP, sub, next);
150     }
151 
152     VTABLE void destroy() {
153         /*
154          * If the compiled code contained any .sub (or .pcc.sub)
155          * subroutines, these subs got installed in the globals
156          * during compiling this bytecode segment.
157          *
158          * These globals still exist, calling them will segfault
159          * as the segment is destroyed now.
160          *
161          * RT#46683 walk the fixups for this segment, locate globals
162          *      and nullify the Sub PMC.
163          * This probably needs a pointer into the globals.
164          *
165          * OTOH - if the global exists - this eval pmc ought
166          *        to be alive and destroy isn't called.
167          */
168         PackFile_Segment  *seg;
169         PackFile_ByteCode *cur_cs;
170         Parrot_Sub_attributes *sub_data;
171 
...

kid51

[jkeenan]

Is there anyone who could evaluate the issues raised in this ticket which originated in the RT system?

Thank you very much.

kid51

[plobsing]

If the sub still exists as a global, the code backing the sub should remain live. Invalidating the sub to avoid a segfault is very, very wrong.

The current solution is to have subs mark the eval_pmc backing them. This is the correct solution, as it exposes the object dependancy to the GC.