https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68210
Bug ID: 68210
Summary: nothrow operator fails to call default new
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
A recent discussion about operator new
(https://gcc.gnu.org/ml/gcc-patches/2015-11/msg00192.html) revealed that the
libstdc++ implementation of the nothrow overload of the operator doesn't
conform to the requirement to "return a pointer obtained as if acquired from
the (possibly replaced) ordinary version." The test case below illustrates
some of the problems.
The requirement quoted above implies that a conforming implementation of the
nothrow overload must call the ordinary form like so:
void* operator new (size_t n, const nothrow_t&) {
try {
return operator new (n);
}
catch (...) {
return 0;
}
}
$ cat t.cpp && ~/bin/gcc-5.1.0/bin/g++ -Wall t.cpp && ./a.out
#include <new>
#include <assert.h>
#include <stdlib.h>
struct MyBadAlloc: std::bad_alloc { };
static bool new_fail;
static bool bad_alloc_thrown;
static unsigned new_called;
static unsigned new_handler_called;
static void new_handler ()
{
if (new_handler_called++)
throw MyBadAlloc ();
}
void* operator new (size_t n)
{
static size_t cntr;
++new_called;
for ( ; ; ) {
if (void *p = new_fail ? 0 : malloc (n + sizeof n)) {
*static_cast<size_t*>(p) = ++cntr;
return static_cast<size_t*>(p) + 1;
}
if (std::new_handler h = std::set_new_handler (0)) {
std::set_new_handler (h);
h ();
}
else {
bad_alloc_thrown = true;
throw MyBadAlloc ();
}
}
}
void operator delete (void *p)
{
if (p)
free (static_cast<size_t*>(p) - 1);
}
int main ()
{
new_called = 0;
void *p = operator new (1, std::nothrow);
assert (p != 0);
assert (1 == new_called);
std::set_new_handler (new_handler);
new_fail = true;
try {
p = operator new (1, std::nothrow);
}
catch (...) {
assert (!"nothrow operator new threw");
}
assert (0 == p);
assert (2 == new_handler_called);
assert (bad_alloc_thrown);
}
a.out: t.cpp:53: int main(): Assertion `1 == new_called' failed.
Aborted (core dumped)
