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3answers
195 views

On a modern compiler, how do I intentionally code for 2s complement with wraparound?

I want to compare sequence numbers (given to this code from elsewhere) that may wrap around. Simply comparing two such values will not handle the case like 0x00000002 being greater than 0xfffffffd, ...
1
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2answers
180 views

Why doesn't the compiler complain when I try to access a non-existent array value?

My C++ book says that if I have int anArray[25]; and I try to evaluate anArray[25] = 0; the program will simply overwrite whatever value is stored in the next memory address past the end of the ...
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1answer
95 views

Consistency of Undefined behavior

If there's a bug that triggers undefined behavior in a piece of code, is the undefined behavior consistent each time running it? and changes each time compiling it? For example if you had some C code ...
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4answers
399 views

When did Undefined Behavior in C jump the causality barrier

Some hyper-modern C compilers will infer that if a program will invoke Undefined Behavior when given certain inputs, such inputs will never be received. Consequently, any code which would be ...
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3answers
132 views

How much can you detect undefined behaviour using testing [closed]

I hope this question fits this site. You may know you can't detect undefined behaviour in C using compilers - and some tools (static analysis) can help you detect it. My question is more empirical - I ...
2
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0answers
207 views

Have any C compilers ever *defined* `unsigned short x=-3; x*=x;` to yield anything other than 9

In a C implementation where int can hold all values of type unsigned short, standard integer promotion rules dictate that given the code: unsigned short x=(USHORT_MAX+1)-3; // Or just -3 x*=x; a ...
9
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4answers
2k views

Undefined behaviour in Java

I was reading this question on SO which discusses some common undefined behavior in C++, and I wondered: does Java also have undefined behaviour? If that is the case, then what are some common causes ...
4
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2answers
269 views

Undefined behaviours in C

Recently I came across a number of undefined features in C, one of them being the following: http://stackoverflow.com/questions/8698048/behaviour-of-non-const-int-pointer-on-a-const-int Could ...
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13answers
4k views

Philosophy behind Undefined Behavior

C\C++ specifications leave out a large number of behaviors open for compilers to implement in their own way. There are a number of questions that always keep getting asked here about the same and we ...
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10answers
3k views

What makes C developers so curious if “i++ == ++i”? [closed]

Just a random observation, it seems that on StackOverflow.com, there are questions about if "++i == i++". That question gets asked all the time though, I think I saw it asked about 6 or 7 times in the ...