为什么浮动"除法被零"例外情况是不是在一个函数抓到,甚至处理设置? [英] Why float "division-by-zero" exception wasn't caught in a function even handler was set?
问题描述
我试着学习在C信号处理,发现了奇怪的行为时。
当x / = Y;在主函数的信号处理工作的上下文中执行。但是,当同样的一些功能(bad_func)执行的处理程序但忽略SIGFPE信号处理程序已经设置。
问:为什么SIGFPE不是在一个函数通过我的全球信号处理程序捕获甚至_control87被称为
(MS 2010 VC):
的#includestdafx.h中
#包括LT&;&stdlib.h中GT;
#包括LT&;&stdio.h中GT;
#包括LT&;&signal.h中GT;
#包括LT&;&SETJMP.H GT;
#包括LT&;&FLOAT.H GT;jmp_buf g_jb_MainFunc;无效hook_zd(int i)以
{
的printf(结果:%I \\ N,I);
longjmp的(g_jb_MainFunc,5);
}
无效bad_func(无效)
{
双x = 0的,Y = 0 .;
卖出期权(hello1);
//中止();
X / = Y;
卖出期权(bye1);
}
INT主(INT ARGC,CHAR *的argv [])
{
双x = 0的,Y = 0 .;
信号(SIGFPE,hook_zd);
信号(SIGABRT,hook_zd);
看跌期权(你好);
_control87(0,_MCW_EM);
中期业绩;
如果(!(RES =的setjmp(g_jb_MainFunc)))
{
//中止();
// X / = Y;
bad_func();
}其他
{
的printf(从这里跳下:%I \\ N,RES);
}
看跌期权(再见); 返回0;
}
它为我,除非我编译优化开启。例如,如果我编译它在命令行 CL mysigtest.cpp
,异常正常工作。但是,如果我编译它 CL / O1 mysigtest.cpp
,那么它不会显示异常。
在拆卸code显示了问题:
bad_func @@ YAXXZ(无效__cdecl bad_func(无效))?
00000000:68 00 00 00 00推偏移?_ 3. C @ _06CKBHOFLC @ hello1 $ @ AA
00000005:E8 00 00 00 00电话_puts
0000000A:68 00 00 00 00推偏移?_ 3. C @ _04EEFJMNKA @ bye1 $ @ AA
0000000F:E8 00 00 00 00电话_puts
00000014:83 08 C4 ADD ESP,8
00000017:C3 RET
该部门已经优化了。尝试将其与优化关闭,或更改 bad_func
以下内容。对我来说,打败优化:
双bad_func(双Y)
{
双X = 0;
卖出期权(hello1);
//中止();
X / = Y;
卖出期权(bye1);
返回X;
}
和来电更改它:
bad_func(0.0);
I've tried to learn the signal handling in C, when found strange behaviour.
When x /= y; executed in the context of the main function the signal handler works. But when the same executed in some function (bad_func) handler is ignored however signal handler for SIGFPE is already set.
Q: Why SIGFPE wasn't caught in a function by my global signal handler even _control87 was called?
(MS VC 2010):
#include "stdafx.h"
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <setjmp.h>
#include <float.h>
jmp_buf g_jb_MainFunc;
void hook_zd (int i)
{
printf("Result :%i\n",i);
longjmp(g_jb_MainFunc, 5);
}
void bad_func(void)
{
double x = 0., y = 0.;
puts("hello1");
//abort();
x /= y;
puts("bye1");
}
int main(int argc, char* argv[])
{
double x = 0., y = 0.;
signal(SIGFPE, hook_zd);
signal(SIGABRT, hook_zd);
puts("hello");
_control87(0, _MCW_EM );
int res;
if (! (res = setjmp(g_jb_MainFunc)))
{
//abort();
//x /= y;
bad_func();
} else
{
printf("Jumped here from: %i\n",res);
}
puts("bye");
return 0;
}
It works for me unless I compile with optimizations turned on. For example, if I compile it from the command line as cl mysigtest.cpp
, the exceptions work as expected. But if I compile it cl /O1 mysigtest.cpp
, then it does not show the exception.
The disassembled code shows the problem:
?bad_func@@YAXXZ (void __cdecl bad_func(void)):
00000000: 68 00 00 00 00 push offset ??_C@_06CKBHOFLC@hello1?$AA@
00000005: E8 00 00 00 00 call _puts
0000000A: 68 00 00 00 00 push offset ??_C@_04EEFJMNKA@bye1?$AA@
0000000F: E8 00 00 00 00 call _puts
00000014: 83 C4 08 add esp,8
00000017: C3 ret
The division has been optimized out. Try it with optimizations turned off, or change bad_func
to the following. For me, it "defeated" the optimizer:
double bad_func(double y)
{
double x = 0.;
puts("hello1");
//abort();
x /= y;
puts("bye1");
return x;
}
And change the call to it:
bad_func( 0.0 );
这篇关于为什么浮动&QUOT;除法被零&QUOT;例外情况是不是在一个函数抓到,甚至处理设置?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!