https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67875
Bug ID: 67875
Summary: missing -Warray-bounds in a default placement new
expression, bogus location on an overload
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
GCC fails to diagnose placement new expressions that attempt to access an array
past its bounds and that involve the default placement operator new:
$ cat t.cpp && g++ -c -O2 -Wall -std=gnu++11 t.cpp
#include <new>
struct A {
char a [4];
} a;
void foo ()
{
new (&a.a [5]) char;
}
$
When the out-of-bounds access involves a user-defined overload of the placement
new operator that makes use of the out-of-bounds pointer, GCC issues an
-Warray-bounds warning that points into the body of the operator instead of the
new expression. (Clang diagnoses both cases correctly.)
$ cat t.cpp && g++ -c -O2 -Wall -std=gnu++11 t.cpp
typedef __typeof__ (sizeof 0) size_t;
extern "C" int printf (const char*, ...);
void* operator new (size_t n, void *p, int) {
printf ("%s: %zu, %p\n", __PRETTY_FUNCTION__, n, p);
return p;
}
struct A { char a [4]; } a;
void foo () {
new (&a.a [5], 0) char;
}
t.cpp: In function ‘void foo()’:
t.cpp:6:56: warning: array subscript is above array bounds [-Warray-bounds]
printf ("%s: %zu, %p\n", __PRETTY_FUNCTION__, n, p);
^
