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[Bug c++/55446] New: array new with size zero vanishes from object code
- From: "jens.maurer at gmx dot net" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 23 Nov 2012 10:48:45 +0000
- Subject: [Bug c++/55446] New: array new with size zero vanishes from object code
- Auto-submitted: auto-generated
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55446
Bug #: 55446
Summary: array new with size zero vanishes from object code
Classification: Unclassified
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: jens.maurer@gmx.net
Host: x86_64-unknown-linux-gnu
Target: x86_64-unknown-linux-gnu
The following program compiles successfully and outputs nothing at all. In
fact, the generated assembly has an empty "main". This happens even when
compiling with -O0.
#include <iostream>
struct S {
S() { }
};
int main()
{
std::cout << new S[0] << " bla" << std::endl;
}
$ g++ new-opt.cc -Wall -Wextra
$ ./a.out
(no output)
The issue goes away when removing the default constructor of "S". It seems gcc
believes array-new with zero size is undefined behavior and thus removes the
rest of the expression. I can't follow the "undefined behavior" part;
array-new with zero size should yield a non-zero pointer (see 3.7.3.1p2
[basic.stc.dynamic.allocation] and 5.3.4p7 [expr.new]).