libgo/runtime/go-defer.c

   1 /* go-defer.c -- manage the defer stack.
   2
   3    Copyright 2009 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 #include <stddef.h>
   8
   9 #include "runtime.h"
  10 #include "go-alloc.h"
  11 #include "go-panic.h"
  12 #include "go-defer.h"
  13
  14 /* This function is called each time we need to defer a call.  */
  15
  16 void
  17 __go_defer (_Bool *frame, void (*pfn) (void *), void *arg)
  18 {
  19   G *g;
  20   struct __go_defer_stack *n;
  21
  22   g = runtime_g ();
  23   n = (struct __go_defer_stack *) __go_alloc (sizeof (struct __go_defer_stack));
  24   n->__next = g->defer;
  25   n->__frame = frame;
  26   n->__panic = g->panic;
  27   n->__pfn = pfn;
  28   n->__arg = arg;
  29   n->__retaddr = NULL;
  30   n->__makefunc_can_recover = 0;
  31   n->__free = 1;
  32   g->defer = n;
  33 }
  34
  35 /* This function is called when we want to undefer the stack.  */
  36
  37 void
  38 __go_undefer (_Bool *frame)
  39 {
  40   G *g;
  41
  42   g = runtime_g ();
  43   while (g->defer != NULL && g->defer->__frame == frame)
  44     {
  45       struct __go_defer_stack *d;
  46       void (*pfn) (void *);
  47       M *m;
  48
  49       d = g->defer;
  50       pfn = d->__pfn;
  51       d->__pfn = NULL;
  52
  53       if (pfn != NULL)
  54         (*pfn) (d->__arg);
  55
  56       g->defer = d->__next;
  57
  58       /* This may be called by a cgo callback routine to defer the
  59          call to syscall.CgocallBackDone, in which case we will not
  60          have a memory context.  Don't try to free anything in that
  61          case--the GC will release it later.  */
  62       m = runtime_m ();
  63       if (m != NULL && m->mcache != NULL && d->__free)
  64         __go_free (d);
  65
  66       /* Since we are executing a defer function here, we know we are
  67          returning from the calling function.  If the calling
  68          function, or one of its callees, paniced, then the defer
  69          functions would be executed by __go_panic.  */
  70       *frame = 1;
  71     }
  72 }
  73
  74 /* This function is called to record the address to which the deferred
  75    function returns.  This may in turn be checked by __go_can_recover.
  76    The frontend relies on this function returning false.  */
  77
  78 _Bool
  79 __go_set_defer_retaddr (void *retaddr)
  80 {
  81   G *g;
  82
  83   g = runtime_g ();
  84   if (g->defer != NULL)
  85     g->defer->__retaddr = retaddr;
  86   return 0;
  87 }