什么原因可能导致dynamic_cast崩溃? [英] What could cause a dynamic_cast to crash?
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问题描述
我有一段代码看起来像这样:
I have a piece of code looking like this :
TAxis *axis = 0;
if (dynamic_cast<MonitorObjectH1C*>(obj))
axis = (dynamic_cast<MonitorObjectH1C*>(obj))->GetXaxis();
有时会崩溃:
Thread 1 (Thread -1208658240 (LWP 11400)):
#0 0x0019e7a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1 0x048c67fb in __waitpid_nocancel () from /lib/tls/libc.so.6
#2 0x04870649 in do_system () from /lib/tls/libc.so.6
#3 0x048709c1 in system () from /lib/tls/libc.so.6
#4 0x001848bd in system () from /lib/tls/libpthread.so.0
#5 0x0117a5bb in TUnixSystem::Exec () from /opt/root/lib/libCore.so.5.21
#6 0x01180045 in TUnixSystem::StackTrace () from /opt/root/lib/libCore.so.5.21
#7 0x0117cc8a in TUnixSystem::DispatchSignals ()
from /opt/root/lib/libCore.so.5.21
#8 0x0117cd18 in SigHandler () from /opt/root/lib/libCore.so.5.21
#9 0x0117bf5d in sighandler () from /opt/root/lib/libCore.so.5.21
#10 <signal handler called>
#11 0x0533ddf4 in __dynamic_cast () from /usr/lib/libstdc++.so.6
我没有线索为什么它崩溃。 obj 不为null(如果它是不会是一个问题,会吗?)。
I have no clue why it crashes. obj is not null (and if it was it would not be a problem, would it ?).
动态转换可能会导致崩溃的原因是什么?
What could be the reason for a dynamic cast to crash ?
如果它不能转换,它应该只返回NULL否?
If it can't cast, it should just return NULL no ?
推荐答案
崩溃的一些可能原因:
-
obj
对象与非多态类型(类或结构没有虚拟方法或基本类型)。 -
obj
指向已释放的对象。 -
obj
指向未映射的内存或已映射的内存, -
obj
指向具有多态类型的对象,但是
obj
points to an object with a non-polymorphic type (a class or struct with no virtual methods, or a fundamental type).obj
points to an object that has been freed.obj
points to unmapped memory, or memory that has been mapped in such a way as to generate an exception when accessed (such as a guard page or inaccessible page).obj
points to an object with a polymorphic type, but that type was defined in an external library that was compiled with RTTI disabled.
并非所有这些问题都会导致所有情况下的崩溃。
Not all of these problems necessarily cause a crash in all situations.
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