integer-overflow

Is there a way to catch integer exceptions with gfortran or ifort like there is for catching floating point exceptions? Consider this simple program to calculate the factorial: program factorial use, intrinsic :: iso_fortran_env implicit none integer(8) :: fac real(REAL64) :: facR integer,parameter :: maxOrder = 30 integer :: i fac = 1 ; facR = 1.e0_REAL64 do i=2,maxOrder fac=fac*i ; facR=facR*real(i,REAL64) write(*,*) i, fac, facR enddo ! i end program At some point there will be an overflow - for integer(8) as shown here, it will occur at around 21. But without the calculation using floats

This question already has an answer here: Overflowing of Unsigned Int 3 answers I write the following code: #include <iostream> using namespace std; int main() { unsigned int i=1; i=i-3; cout<<i; return 0; } The output is a garbage value, which is understandable. Now I write the following code: #include <iostream> using namespace std; int main() { unsigned int i=1; i=i-3; i=i+5; cout<<i; return 0; } Now the output is 3. What's happening here? How is the garbage value being added by 5 here? Think of the values of unsigned int being drawn on a large clock face with the largest possible value

Ok, so I have some problems with C++ iostreams that feels very odd, but it is probably defined behaviour, considering this happens with both MSVC++ and G++. Say I have this program: #include <iostream> using namespace std; int main() { int a; cin >> a; cout << a << endl; cin >> a; cout << a << endl; return 0; } If I intentionally overflow by giving the first cin a value that is larger than the max limit of an int, all further calls to cin.operator>>() will immediately return for some reason, and a is set to some value. The value seems to be undefined. Why, and where is this behavior documented

Swift has integer overflow arithmetic functions which return a flag whether the number has overflowed or not. Do we have same thing in Rust? huon As you note, there are intrinsics for this but these are unsafe and somewhat annoying to use. Before Rust 1.0, the standard library provided wrappers that detect the overflow for the 4 arithmetic operations in the form of CheckedAdd , CheckedSub , CheckedMul and CheckedDiv . As of Rust 1.0, these traits no longer exist and there are just inherent methods on each numeric type, such as i32::checked_add . However, these just detect overflow and do not

Let say I have a 32-bit machine. I know during integer promotion the expressions are converted to:\ int if all values of the original type can be represented in int unsigned otherwise Could you please explain what will happen for the following expression? and In general, how ranking works here? First snippet: si16 x, pt; si32 speed; u16 length; x = (speed*pt)/length; Second one: x = pt + length; EDIT: si16 means signed short (size 16 bit), si32 bit means signed int (size 32 bit) and u16 means unsigned short (size 16) I found the following link that has described the issue very clearly:

I was writing a program in C++ to find all solutions of a b = c , where a , b and c together use all the digits 0-9 exactly once. The program looped over values of a and b , and it ran a digit-counting routine each time on a , b and a b to check if the digits condition was satisfied. However, spurious solutions can be generated when a b overflows the integer limit. I ended up checking for this using code like: unsigned long b, c, c_test; ... c_test=c*b; // Possible overflow if (c_test/b != c) {/* There has been an overflow*/} else c=c_test; // No overflow Is there a better way of testing for

When compiling the following with the strict overflow flag, it tells me, on the 2nd test that r may not be what I think it could be: int32_t r(my_rand()); if(r < 0) { r = -r; if(r < 0) { // <-- error on this line r = 0; } } The error is: /build/buildd/libqtcassandra-0.5.5/tests/cassandra_value.cpp: In function 'int main(int, char**)': /build/buildd/libqtcassandra-0.5.5/tests/cassandra_value.cpp:2341:13: error: assuming signed overflow does not occur when simplifying conditional to constant [-Werror=strict-overflow] if(r < 0) { ^ What I do not understand is: why wouldn't the error be generated