Questions tagged [undefined-behavior]
The undefined-behavior tag has no usage guidance.
15 questions
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In C++, does dereferencing a nullptr itself cause undefined behaviour, or is it the acting upon the dereferenced pointer which is undefined?
I happen to have a reason why I might want to dereference a nullptr.
Of course when I do, my program crashes, and from what I gather, this is due to the compiler playing it safe and stopping my ...
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Finding undefined behaviour in C for embedded system
I just started at a small company and there is a hot-needle-built software for micro controllers written in C which we are now starting to clean up to make it maintainable again.
Of course this goes ...
user233741
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Why does C++ have 'undefined behaviour' (UB) and other languages like C# or Java don't?
This Stack Overflow post lists a fairly comprehensive list of situations where the C/C++ language specification declares as to be 'undefined behaviour'. However, I want to understand why other modern ...
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Adding new parameter to Javascript function
What do I pass in for the existing arguments that have no value, undefined or null?
Existing function foo(a, b) is called like foo(1) and foo(23, "hi"). After adding a new parameter, it's foo(a, b, ...
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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, ...
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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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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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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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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 ...
user185707
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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 ...
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Undefined behavior, in principle
Whether in C or C++, I think that this illegal program, whose behavior according to the C or C++ standard is undefined, is interesting:
#include <stdio.h>
int foo() {
int a;
const int ...
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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 ...
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Undefined behaviours in C
Recently I came across a number of undefined features in C, one of them being the following:
https://stackoverflow.com/questions/8698048/behaviour-of-non-const-int-pointer-on-a-const-int
Could ...
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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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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 ...
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