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
  13 /* This function is called each time we need to defer a call.  */
  14
  15 void
  16 __go_defer (_Bool *frame, void (*pfn) (void *), void *arg)
  17 {
  18   G *g;
  19   Defer *n;
  20
  21   g = runtime_g ();
  22   n = runtime_newdefer ();
  23   n->next = g->_defer;
  24   n->frame = frame;
  25   n->_panic = g->_panic;
  26   n->pfn = (uintptr) pfn;
  27   n->arg = arg;
  28   n->retaddr = 0;
  29   n->makefunccanrecover = 0;
  30   n->special = 0;
  31   g->_defer = n;
  32 }
  33
  34 /* This function is called when we want to undefer the stack.  */
  35
  36 void
  37 __go_undefer (_Bool *frame)
  38 {
  39   G *g;
  40
  41   g = runtime_g ();
  42   while (g->_defer != NULL && g->_defer->frame == frame)
  43     {
  44       Defer *d;
  45       void (*pfn) (void *);
  46
  47       d = g->_defer;
  48       pfn = (void (*) (void *)) d->pfn;
  49       d->pfn = 0;
  50
  51       if (pfn != NULL)
  52         (*pfn) (d->arg);
  53
  54       g->_defer = d->next;
  55
  56       /* This may be called by a cgo callback routine to defer the
  57          call to syscall.CgocallBackDone, in which case we will not
  58          have a memory context.  Don't try to free anything in that
  59          case--the GC will release it later.  */
  60       if (runtime_m () != NULL)
  61         runtime_freedefer (d);
  62
  63       /* Since we are executing a defer function here, we know we are
  64          returning from the calling function.  If the calling
  65          function, or one of its callees, paniced, then the defer
  66          functions would be executed by __go_panic.  */
  67       *frame = 1;
  68     }
  69 }
  70
  71 /* This function is called to record the address to which the deferred
  72    function returns.  This may in turn be checked by __go_can_recover.
  73    The frontend relies on this function returning false.  */
  74
  75 _Bool
  76 __go_set_defer_retaddr (void *retaddr)
  77 {
  78   G *g;
  79
  80   g = runtime_g ();
  81   if (g->_defer != NULL)
  82     g->_defer->retaddr = (uintptr) __builtin_extract_return_addr (retaddr);
  83   return 0;
  84 }