Divide by zero does not crash

I noticed that my application does not crash when there is a divide by zero. For example, the following test code:

int i; i = 10/0; printf("i = %d\n", i);


i = 0

It does not crash.

Is there a way to make the application crash when there is a divide by zero? I am running Linux 2.4.26 on a powerpc (MPC8248). I compile with powerpc-linux-gcc.

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Because it's a "div" operation on integer.

Use float instead of int.



Dirk Heinrichs          | Tel:  +49 (0)162 234 3408
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Dirk Heinrichs

It's evaluated on compile time. So it can't crash (but it should result in a compiler error or warning).


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Michael Schnell

This does give a warning at compile time because the constant zero is there. What concerns me is when the denominator is a variable that takes the value of zero while the application is running. There is neither a compilation warning nor any indication that a divide by zero is occurring when the application is running.

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Bill wrote in news: snipped-for-privacy@e10g2000prf.googlegroups.com:

The behavior of integer division by 0 is undefined per the C Language standard and, hence, implementation-dependent. On x86, division by 0 produces a hardware exception. On x86 linux, this exception is presented to the program as a signal. However, a conforming implementation may choose to do anything else that is convenient: nothing (leave quotient unmodified), produce random value for the quotient, kill the process.


Reply to
Gil Hamilton

So PUT IN A TEST!!! if (x==0) { fprintf(stderr,"Divide by zero.\n"); exit; } else i=10/x;

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The compiler could insert code that crashes (or produces a signal or whatever behaviour is deemed appropriate) at run-time. But it does not, because the behaviour when not doing an evaluation at compile-time is not to crash or produce a signal. In contrast, on an AMD64 box I also get a warning at compile-time, and a SIGFPE at run-time.

Yes, that's a property of the PowerPC archictecture. AFAIK the theory of the hardware designers was that the compiler should produce code equivalent to:

q=n/d; if (d == 0) raise(SIGFPE);

The idea is that the check would be performed during the latency of the division, so it would usually not cost extra time. So one could make the hardware simpler by not putting in the check there. I may be confusing PowerPC with another RISC architecture (most likely MIPS) wrt this aspect, though.

But obviously gcc does not do this (there does not even seem to be an option to turn this on). Do other C compilers for PowerPC (from IBM, Apple or Motorola generate such code)?

Followups set to comp.os.linux.powerpc.

- anton

M. Anton Ertl                    Some things have to be seen to be believed
anton@mips.complang.tuwien.ac.at Most things have to be believed to be seen
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Anton Ertl

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