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70 lines
2.0 KiB
C
70 lines
2.0 KiB
C
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/* go-recover.c -- support for the go recover function.
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Copyright 2010 The Go Authors. All rights reserved.
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Use of this source code is governed by a BSD-style
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license that can be found in the LICENSE file. */
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#include "interface.h"
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#include "go-panic.h"
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#include "go-defer.h"
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/* This is called by a thunk to see if the real function should be
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permitted to recover a panic value. Recovering a value is
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permitted if the thunk was called directly by defer. RETADDR is
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the return address of the function which is calling
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__go_can_recover--this is, the thunk. */
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_Bool
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__go_can_recover (const void* retaddr)
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{
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struct __go_defer_stack *d;
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const char* ret;
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const char* dret;
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if (__go_panic_defer == NULL)
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return 0;
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d = __go_panic_defer->__defer;
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if (d == NULL)
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return 0;
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/* The panic which this function would recover is the one on the top
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of the panic stack. We do not want to recover it if that panic
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was on the top of the panic stack when this function was
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deferred. */
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if (d->__panic == __go_panic_defer->__panic)
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return 0;
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/* D->__RETADDR is the address of a label immediately following the
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call to the thunk. We can recover a panic if that is the same as
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the return address of the thunk. We permit a bit of slack in
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case there is any code between the function return and the label,
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such as an instruction to adjust the stack pointer. */
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ret = (const char *) retaddr;
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dret = (const char *) d->__retaddr;
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return ret <= dret && ret + 16 >= dret;
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}
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/* This is only called when it is valid for the caller to recover the
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value on top of the panic stack, if there is one. */
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struct __go_empty_interface
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__go_recover ()
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{
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struct __go_panic_stack *p;
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if (__go_panic_defer == NULL
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|| __go_panic_defer->__panic == NULL
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|| __go_panic_defer->__panic->__was_recovered)
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{
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struct __go_empty_interface ret;
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ret.__type_descriptor = NULL;
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ret.__object = NULL;
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return ret;
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}
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p = __go_panic_defer->__panic;
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p->__was_recovered = 1;
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return p->__arg;
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}
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