Integer overflow occurs when the result of an operation is larger than the maximal value that can be represented by the underlying integer type.
Questions tagged [integer-overflow]
1056 questions
13
votes
6 answers
Absolute value of INT_MIN
How could I extract the absolute value of INT_MIN without overflowing? See this code for the problem:
#include
#include
#include
int main(void) {
printf("INT_MAX: %d\n", INT_MAX);
printf("INT_MIN: %d\n",…
Morgan Wilde
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11 answers
C++ Template for safe integer casts
I am trying to write a C++ template function that will throw a runtime exception on integer overflow in casts between different integral types, with different widths, and possible signed/unsigned mismatch. For these purposes I'm not concerned with…
JSBձոգչ
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4 answers
No useful and reliable way to detect integer overflow in C/C++?
No, this is not a duplicate of How to detect integer overflow?. The issue is the same but the question is different.
The gcc compiler can optimize away an overflow check (with -O2), for example:
int a, b;
b = abs(a); // will…
A Fog
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12
votes
2 answers
get unsigned long long addition carry
I want to get the carry bit of adding two unsigned 64-bit integers in c.
I can use x86-64 asm if needed.
code:
#include
typedef unsigned long long llu;
int main(void){
llu a = -1, b = -1;
int carry = /*carry of a+b*/;
llu res =…
neo5003
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12
votes
4 answers
what's the difference between mid=(beg+end)/2 and mid=beg+(end-beg)/2 in binary search?
It is a problem from C++ primer fifth edition problem 3.26, I don't know the difference between them ?
May be the second one can avoid overflow.
Pegasus
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12
votes
7 answers
Explanation of the safe average of two numbers
Whenever I need to average two numbers for an algorithm like binary search, I always do something like this:
int mid = low + ((high - low) / 2);
I recently saw another way to do it in this post, but I don't understand it. It says you can do this in…
gsgx
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12
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1 answer
long long is 8 bytes, but I get integer overflow?
Suppose
long long b = 5*1024*1024*1024; // 5 gigs, small enough for 64 bits
printf ("%lu\n",sizeof(long long)); // prints 8 (bytes) = 64 bits
but the compiler complains:
warning: integer overflow in expression [-Woverflow]
Why does it…
Dervin Thunk
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12
votes
3 answers
How to check if a number overflows an 'int'
Possible Duplicate:
Best way to detect integer overflow in C/C++
I was asked this question in an interview : "Convert a string representation of a number into an integer". But if the number exceeds the max value that can be stored in a 32 bit…
AlgoMan
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12
votes
3 answers
Clojure - Calculate with big numbers
I want to calculate !1000 in clojure, how can I do this without getting a integer-overflow exception?
My factorial code is right now: (reduce * (range 1 1001)).
Sawny
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11
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3 answers
executing a process with argc=0
Is it possible to execute a process whose argc = 0? I need to execute a program but it is extremely important for its argc to be equal to 0. Is there a way to do that?
I tried to put 2^32 arguments in the command line so that it appears as if argc =…
Keeto
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11
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4 answers
How to implement wrapping signed int addition in C
This is a complete rewrite of the question. Hopefully it is clearer now.
I want to implement in C a function that performs addition of signed ints with wrapping in case of overflow.
I want to target mainly the x86-64 architecture, but of course the…
Federico
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11
votes
1 answer
how to add a negative i32 number to an usize variable?
Such as:
let mut a : usize = 0xFF;
a += -1; // -1 may be from other variable, so there can't be a -= 1;
println!("{}", a);
The output is:
error[E0277]: the trait bound `usize: std::ops::Neg` is not satisfied
anyway?
Excosy S.P.
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11
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2 answers
Does C++ have an equivalent to boost::numeric_cast(SourceType)?
I am doing a bunch of applied-mathematics/signal-processing/algorithms C++ code.
I have enabled the -Wconversion compiler warning to catch issues like runtime conversion of numbers that are type double to type int32_t.
Obviously I am always…
Trevor Boyd Smith
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11
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1 answer
SAT solving with more than 2^32 clauses
I'm trying to solve a big CNF formula using a SAT solver. The formula (in DIMACS format) has 4,697,898,048 = 2^32 + 402,930,752 clauses, and all SAT solvers I could find are having trouble with it:
(P)lingeling reports that there are "too many…
Dominik Peters
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10
votes
5 answers
Simulating integer overflow in Python
Python 2 has two integer datatypes int and long, and automatically converts between them as necessary, especially in order to avoid integer overflow.
I am simulating a C function in Python and am wondering if there are standard ways to re-enable…
brannerchinese
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