gc: put limit on size of exported recursive interface

Prevents edge-case recursive types from consuming excessive memory.

Fixes #1909.

R=golang-dev, lvd, rsc
CC=golang-dev
https://golang.org/cl/5504108

diff --git a/src/cmd/gc/fmt.c b/src/cmd/gc/fmt.c
index f3be53c8fbf21bfdd4fedf1456b69f740ea6dbdb..3013d0d3293b78ff29d81d232704d403ea898859 100644 (file)
--- a/src/cmd/gc/fmt.c
+++ b/src/cmd/gc/fmt.c
@@ -1450,7 +1450,7 @@ Tconv(Fmt *fp)
        if(t == T)
                return fmtstrcpy(fp, "<T>");
 
-       if(t->trecur > 4)
+       if(t->trecur > 4 || fp->nfmt > 1000)
                return fmtstrcpy(fp, "<...>");
 
        t->trecur++;