runtime: do not garbage collect windows callbacks

Fixes #1883.
Fixes #1702.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/4532103

diff --git a/src/pkg/runtime/windows/thread.c b/src/pkg/runtime/windows/thread.c
index 2ce92dcfbfd969ac2bb3d995d6f4fb749afd14db..2ce8fae15a324881b08b2eed0a4d4dd9a9e8074a 100644 (file)
--- a/src/pkg/runtime/windows/thread.c
+++ b/src/pkg/runtime/windows/thread.c
@@ -324,13 +324,31 @@ runtime·ctrlhandler1(uint32 type)
        return 0;
 }
 
+// Will keep all callbacks in a linked list, so they don't get garbage collected.
+typedef        struct  Callback        Callback;
+struct Callback {
+       Callback*       link;
+       void*           gobody;
+       byte            asmbody;
+};
+
+typedef        struct  Callbacks       Callbacks;
+struct Callbacks {
+       Lock;
+       Callback*       link;
+       int32           n;
+};
+
+static Callbacks       cbs;
+
 // Call back from windows dll into go.
 byte *
 runtime·compilecallback(Eface fn, bool cleanstack)
 {
        Func *f;
        int32 argsize, n;
-       byte *ret, *p;
+       byte *p;
+       Callback *c;
 
        if(fn.type->kind != KindFunc)
                runtime·panicstring("not a function");
@@ -348,7 +366,23 @@ runtime·compilecallback(Eface fn, bool cleanstack)
        if(cleanstack)
                n += 2;         // ... argsize
 
-       ret = p = runtime·mal(n);
+       runtime·lock(&cbs);
+       for(c = cbs.link; c != nil; c = c->link) {
+               if(c->gobody == fn.data) {
+                       runtime·unlock(&cbs);
+                       return &c->asmbody;
+               }
+       }
+       if(cbs.n >= 20)
+               runtime·throw("too many callback functions");
+       c = runtime·mal(sizeof *c + n);
+       c->gobody = fn.data;
+       c->link = cbs.link;
+       cbs.link = c;
+       cbs.n++;
+       runtime·unlock(&cbs);
+
+       p = &c->asmbody;
 
        // MOVL fn, AX
        *p++ = 0xb8;
@@ -376,7 +410,7 @@ runtime·compilecallback(Eface fn, bool cleanstack)
        } else
                *p = 0xc3;
 
-       return ret;
+       return &c->asmbody;
 }
 
 void