acid: fix memory corruption due to gc

we cannot call gc() in execute() because it will gc
anonyous intermediate results which happens when we
construct a list and the elements are calculated by
calling a function thru ocall() which calls execute().

also, the _thiscmd symbol; which is used to keep
a reference to a statement so it wont get garbage
collected; does not work as yyparse() is recursive
(include statements).

we add execrec() function which *only* gets called from
yyparse() when evaluating a statement. it will
keep a stack on the _thiscmd symbol handling the yyparse()
recursion.

we also only call gc() in execrec() before calling
execute(). so execute() will never gc() while evaluating
a statement which prevents the intermediate results
from getting collected.

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/src/cmd/acid/acid.h b/sys/src/cmd/acid/acid.h
index 897a0cc50..bd0d6b7cb 100644
--- a/sys/src/cmd/acid/acid.h
+++ b/sys/src/cmd/acid/acid.h
@@ -190,6 +190,7 @@ void	dostop(int);
 Lsym*	enter(char*, int);
 void	error(char*, ...);
 void	execute(Node*);
+void	execrec(Node*);
 void	fatal(char*, ...);
 void	flatten(Node**, Node*);
 void	gc(void);