Re: STL objects and binary compatibility
On 13 Mai, 01:35, Paavo Helde <nob...@ebi.ee> wrote:
Maybe I should have been more precise. The alarms are not "false" in the
sense that the code has UB by the standard. On the other hand, the code
appears to have defined meaning and guaranteed behavior by the same
implementation which raises the alarms. Example 1:
#include <vector>
#include <iostream>
#include <ostream>
double summate(const double* from, const double* to) {
double sum=0.0;
for(const double* p=from; p!=to; ++p) {
sum += *p;
}
return sum;
}
int main() {
std::vector<double> v;
v.push_back(3.1415926);
v.push_back(2.7182818);
size_t n=v.size();
std::cout << summate(&v[0], &v[n]) << "\n";
}
In real life, summate() is some legacy function accepting double*
pointers, which has to be interfaced with a new std::vector array used
for better memory management. The expression &v[n] is formally UB. VC++
on XP crashes the application with the message "test.exe has encountered
a problem and needs to close. We are sorry for the inconvenience.". If
_SECURE_SCL is defined to 0, the program runs nicely and produces the
expected results.
I think the problem is not only formal in this case, because the
expression v[n], or v.operator[](n) dereferences an invalid pointer.
Okay, the program may happen to work, but the checked iterator alarm/
crash is justified by the fact that it exposes a potential problem
that could easily be avoided by using (&v[0] + n) instead of &v[n].
--
DP
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