[Bug c++/49850] New: Implicit creation of a temporary object when a constant reference is passed as parameter and the actual and formal types are not identical
gccbugs@andreas-borchert.de
gcc-bugzilla@gcc.gnu.org
Tue Jul 26 09:27:00 GMT 2011
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49850
Summary: Implicit creation of a temporary object when a
constant reference is passed as parameter and the
actual and formal types are not identical
Product: gcc
Version: 4.4.5
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: gccbugs@andreas-borchert.de
The following has been tested with g++ (Debian 4.4.5-8) 4.4.5 for the amd64
architecture as shipped with stable Debian 6.0. I do not have it tested for
newer releases as I do not have them conveniently available. Following code
demonstrates the problem:
---- code start ----
#include <iostream>
#include <sys/types.h>
using namespace std;
size_t si;
void foo(const unsigned int& ui) {
cout << "address of ui = " << (long long int) &ui << endl;
}
int main() {
cout << "address of si = " << (long long int) &si << endl;
foo(si);
}
---- code end ----
The code generated for the invocation of foo() in main() shows
the problem:
movq si(%rip), %rax
movl %eax, -20(%rbp)
leaq -20(%rbp), %rax
movq %rax, %rdi
call _Z3fooRKj
Instead of passing the address of the global si variable, a temporary
object is created (at 20(%rbp)) whose address is passed. If you test
this program, the output shows the effect:
address of si = 6295456
address of ui = 140734739682956
The apparent problem is that "unsigned int" and "size_t" do not match,
at least not on this platform (size and signedness are different). But
then I would expect an error and not the implicit creation of a
temporary object of the appropriate type.
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