Is there any problem with throwing an object constructed on the stack in a try-block by non-const reference, catching it and modifying it, then throwing it by reference to another catch block? Below is a short example of what I'm refering to. struct EC { EC(string msg) { what = msg; } string where; string what; void ap...
#include <iostream> #include <cmath> #define max(x,y) (x)>(y)? (x): (y) int main() { int i = 10; int j = 5; int k = 0; k = max(i++,++j); std::cout << i << "\t" << j << "\t" << k << std::endl; } ...
This code has an interesting bug: some_struct struct_array1[10] = {0}; some_struct struct_array2[10] = {0} int i; for (i = 0; i < sizeof(struct_array1) / sizeof(struct_array1[0]); struct_array1[i].value = struct_array2[i++].value = 1) ; For most compilers, the above code results in setting the "value" field of all str...
Consider the following code: #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <algorithm> using namespace std; int main() { string myAry[] = { "Mary", "had", "a", "Little", "Lamb" }; const size_t numStrs = sizeof(myStr)/sizeof(myAry[0]); v...
This question arose in the comments of a now-deleted answer to this other question. Our question was asked in the comments by STingRaySC as: Where exactly do we invoke UB? Is it calling a member function through an invalid pointer? Or is it calling a member function that accesses member data through an invalid pointer? With the ans...
Consider the following code: struct Calc { Calc(const Arg1 & arg1, const Arg2 & arg2, /* */ const ArgN & argn) : arg1(arg1), arg2(arg2), /* */ argn(argn), coef1(get_coef1()), coef2(get_coef2()) { } int Calc1(); int Calc2(); int Calc3(); private: const Arg1 & arg1; const Arg2 & arg2; // ... const...
Hi We are currently developing an application for a msp430 MCU, and are running into some weird problems. We discovered that declaring arrays withing a scope after declaration of "normal" variables, sometimes causes what seems to be undefined behavior. Like this: foo(int a, int *b); int main(void) { int x = 2; int arr[5]; ...
As far as I understand the wording in 5.2.9 Static cast, the only time the result of a void*-to-object-pointer conversion is allowed is when the void* was a result of the inverse conversion in the first place. Throughout the standard there is a bunch of references to the representation of a pointer, and the representation of a void poi...
Hi everyone. I'm writing a class, and this doubt came up. Is this undef. behaviour? On the other hand, I'm not sure its recommended, or if its a good practice. Is it one if I ensure no exceptions to be thrown in the init function? //c.h class C{ float vx,vy; friend void init(C& c); public: C(); }; //c.cpp C::C() { in...
I've been messing around with string.replace and I noticed something very odd with Webkit and Firebug's javascript consoles. I can repeat this behavior in a blank browser window. (Look at the first and last lines) >>> "/literature?page=".replace(/page=/i, "page=2") "/literature?page=" >>> "/literature?page=".replace("page=", "page=2"...
As mentioned in this answer simply calling the destructor for the second time is already undefined behavior 12.4/14(3.8). For example: class Class { public: ~Class() {} }; // somewhere in code: { Class* object = new Class(); object->~Class(); delete object; // UB because at this point the destructor call is attempted ag...
Many bad things happened and continue to happen (or not, who knows, anything can happen) due to undefined behavior. I understand that this was introduced to leave some wiggle-room for compilers to optimize, and maybe also to make C++ easier to port to different platforms and architectures. However the problems caused by undefined behavio...
Some old code that I just came across: MLIST * new_mlist_link() { MLIST *new_link = (MLIST * ) malloc(sizeof(MLIST)); new_link->next = NULL; new_link->mapi = NULL; new_link->result = 0; } This was being called to build a linked list, however I noticed there is no statement: return new_link; Even without the return...
I've read a lot, including here on SO that suggests this is a very bad idea in general and that the only thing you can do safely is exit the program. I'm not sure that this is true. This is for a pooling memory allocator that hands off large allocations to malloc. During pool_free() a pointer needs to be checked it it belongs to a pool ...
When a is undefined, then a || 1 will throw an error, but a = a || 1 will not. Isn't that a little bit inconsistent? irb(main):001:0> a NameError: undefined local variable or method 'a' for main:Object from (irb):1 from c:/ruby/bin/irb:12:in '<main>' irb(main):002:0> a || 1 NameError: undefined local variable or method...
Regarding division by zero, the standards say: C99 6.5.5p5 - The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined. C++03 5.6.4 - The binary / opera...
Is there any way to know if you program has undefined behavior in C++ (or even C), short of memorizing the entire spec? The reason I ask is that I've noticed a lot of cases of programs working in debug but not release being due to undefined behavior. It would be nice if there were a tool to at least help spot UB, so we know there's the...
It is widely known that adding declarations/definitions to namespace std results in undefined behavior. The only exception to this rule is for template specializations. What about the following "hack"? #include <iostream> namespace std_ { void Foo() { std::clog << "Hello World!" << std::endl; } using namespace std; } int...
Possible Duplicate: Take the address of a one-past-the-end array element via subscript: legal by the C++ Standard or not? int array[10]; int* a = array + 10; // well-defined int* b = &array[10]; // not sure... Is the last line valid or not? ...
ATL::CComVariant has a handful of assignment operators. What I see in the implementation is that in assignment operators accepting LPCOLESTR, IUnknown* or IDispatch* the first action is to call Clear(). If the operator in invoked in such a way that a member variable of the same object is passed CComVariant variant; variant = L"string...