shithub: riscv

Info  •  Files  •  Log  •  Branches

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.

--- a/sys/src/cmd/acid/acid.h

+++ b/sys/src/cmd/acid/acid.h

@@ -190,6 +190,7 @@

 Lsym*	enter(char*, int);

 void	error(char*, ...);

 void	execute(Node*);

+void	execrec(Node*);

 void	fatal(char*, ...);

 void	flatten(Node**, Node*);

 void	gc(void);

--- a/sys/src/cmd/acid/dbg.y

+++ b/sys/src/cmd/acid/dbg.y

@@ -50,11 +50,7 @@

 bigstmnt	: stmnt

 		{

-			/* make stmnt a root so it isn't collected! */

-			mkvar("_thiscmd")->proc = $1;

-			execute($1);

-			mkvar("_thiscmd")->proc = nil;

-			gc();

+			execrec($1);

 			if(interactive)

 				Bprint(bout, "acid: ");

 		}

--- a/sys/src/cmd/acid/exec.c

+++ b/sys/src/cmd/acid/exec.c

@@ -57,6 +57,32 @@

 }

 void

+execrec(Node *n)

+{

+	Value *v;

+	Lsym *s;

+

+	/* make node a root so it isn't collected! */

+	s = mkvar("_thiscmd");

+

+	v = gmalloc(sizeof(Value));

+	memset(v, 0, sizeof(Value));

+	v->type = TCODE;

+	v->cc = n;

+	v->pop = s->v;

+

+	s->v = v;

+	s->proc = n;

+

+	gc();

+	execute(n);

+

+	s->proc = s->v->cc;

+	s->v = v->pop;

+	free(v);

+}

+

+void

 execute(Node *n)

 {

 	Value *v;

@@ -66,7 +92,6 @@

 	Node res, xx;

 	static int stmnt;

-	gc();

 	if(gotint)

 		error("interrupted");

--- a/sys/src/cmd/acid/lex.c

+++ b/sys/src/cmd/acid/lex.c

@@ -569,11 +569,11 @@

 	s->lexval = t;

 	v = gmalloc(sizeof(Value));

-	s->v = v;

-

+	memset(v, 0, sizeof(Value));

 	v->fmt = 'X';

 	v->type = TINT;

-	memset(v, 0, sizeof(Value));

+

+	s->v = v;

 	return s;

 }