[Bug middle-end/103993] -Wismatched-new-delete due to difference in inlining decisions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103993
cdfrey at foursquare dot net changed:
What|Removed |Added
CC||cdfrey at foursquare dot net
--- Comment #5 from cdfrey at foursquare dot net ---
This happens for me. Here is a test case, for gcc 13.1.0, which gives the
warning with this command:
/home/gcc/rootdir/gcc-13.1.0/bin/g++ -Wall -O2 --std=c++17 -Wall -Wextra
-Werror -fmax-errors=4 -c -o gcc-test-case.o gcc-test-case.cc
gcc-test-case.cc: In function ‘int main()’:
gcc-test-case.cc:49:16: error: ‘static void Test::operator delete(void*)’
called on pointer returned from a mismatched allocation function
[-Werror=mismatched-new-delete]
49 | delete t;
|^
In static member function ‘static void* Test::operator new(size_t)’,
inlined from ‘int main()’ at gcc-test-case.cc:48:10:
gcc-test-case.cc:17:30: note: returned from ‘void* malloc(size_t)’
17 | return malloc(size);
|~~^~
gcc-test-case.cc: In function ‘int main()’:
gcc-test-case.cc:48:17: error: ‘static void Test::operator delete(void*)’
called on pointer returned from a mismatched allocation function
[-Werror=mismatched-new-delete]
48 | t = new Test;
| ^~~~
In static member function ‘static void* Test::operator new(size_t)’,
inlined from ‘int main()’ at gcc-test-case.cc:48:10:
gcc-test-case.cc:17:30: note: returned from ‘void* malloc(size_t)’
17 | return malloc(size);
|~~^~
cc1plus: all warnings being treated as errors
make: *** [: gcc-test-case.o] Error 1
The code:
#include // cout statements needed to trigger warning
#include
#include
using namespace std;
struct Test
{
double a, b, c;
Test() {
cout << "Test::Test()\n";
}
void* operator new(size_t size)
{
cout << "Test::operator new(" << size << ")\n";
return malloc(size);
}
void* operator new(size_t size, align_val_t al)
{
cout << "Test::operator new(" << size << ", align: " <<
(size_t)al << ")\n";
return aligned_alloc((size_t)al, size);
}
void* operator new(size_t size, const std::nothrow_t &) throw()
{
cout << "Test::operator new(" << size << ", nothrow)\n";
return malloc(size);
}
void operator delete(void *p)
{
cout << "Test::operator delete()\n";
free(p);
}
void operator delete(void *p, align_val_t al)
{
cout << "Test::operator delete(p, align: " << (size_t)al <<
")\n";
free(p);
}
};
int main(void)
{
Test *t;
t = new Test;
delete t;
}
[Bug middle-end/103993] -Wismatched-new-delete due to difference in inlining decisions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103993
--- Comment #4 from Ed Catmur ---
And another example, provoked by throwing new (this only happens at -Og):
#include
struct D {
D();
static void* operator new (std::size_t s) {
if (void* p = ::malloc(s))
return p;
throw "bad_alloc";
}
static void operator delete (void* p) { ::free(p); }
};
int main() { new D; }
[Bug middle-end/103993] -Wismatched-new-delete due to difference in inlining decisions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103993
andre at kostur dot net changed:
What|Removed |Added
CC||andre at kostur dot net
--- Comment #3 from andre at kostur dot net ---
Here's a smaller, minimal example of the issue (as described in the subject):
#include
struct Foo {
static void * operator new( size_t s ) __attribute__( ( noinline ) ) {
return ::operator new( s );
}
static void operator delete( void * p ) { return ::operator delete( p ); }
};
int
main() {
Foo * f = new Foo();
delete f;
}
[Bug middle-end/103993] -Wismatched-new-delete due to difference in inlining decisions
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103993
Martin Sebor changed:
What|Removed |Added
Blocks||100406
CC||msebor at gcc dot gnu.org
See Also||https://gcc.gnu.org/bugzill
||a/show_bug.cgi?id=100861
Summary|Incorrect error generated |-Wismatched-new-delete due
|by mismatched-new-delete|to difference in inlining
||decisions
Keywords||diagnostic
Component|c++ |middle-end
--- Comment #2 from Martin Sebor ---
The reported mismatch is between
void operator delete [](void*)
and
void* ACE_Svc_Handler::operator new(size_t)
i.e., the array form of the global operator delete is being called on the
result of a scalar member operator new. The deallocation function
corresponding to a member array new is a member array delete, so the warning
isn't incorrect per se.
The warning is based on the compiler's view of the optimized code, after
inlining and other transformations. If the program provides overloads of
operators new and delete for some type and GCC inlines a call to one but not
the other, the warning will trigger because it sees a mismatch. To avoid this
problem either prevent the inlining of both the allocation and the deallocation
function (using attribute noinline), or force both to be inlined (by declaring
them inline and attribute always_inline). The diff below shows the latter
solution. It's possible for GCC do the former automatically (and it does that
for a subset of these cases) but given it's not without a performance cost it
seems preferable to leave the choice up to the programmer. Another approach
was suggested in pr101829. See also pr100861 for a discussions of another
similar issue.
(When reporting a problem it's helpful to explain why you think it's in GCC
rather than in the submitted test case so we don't have to guess.)
$ diff -u JSimpleProcess.C JSimpleProcess-fix.C
--- JSimpleProcess.C2022-01-12 11:06:52.787461649 -0700
+++ JSimpleProcess-fix.C2022-01-12 11:18:30.085356124 -0700
@@ -78365,7 +78365,8 @@
;
return;
}
-template void *
+template
+inline __attribute__ ((always_inline)) void *
ACE_Svc_Handler::operator new (size_t n)
{
;
@@ -78378,10 +78379,11 @@
else
{
dynamic_instance->set ();
- return ::new char[n];
+ return ::operator new (n);
}
}
-template void *
+template
+inline __attribute__ ((always_inline)) void *
ACE_Svc_Handler::operator new (size_t n,
const
::std::nothrow_t&) throw()
{
@@ -78395,15 +78397,16 @@
else
{
dynamic_instance->set ();
- return ::new(::std::nothrow) char[n];
+ return ::operator new(n, ::std::nothrow);
}
}
-template void
+template
+inline __attribute__ ((always_inline)) void
ACE_Svc_Handler::operator delete (void *p,
const ::std::nothrow_t&) throw()
{
;
- ::delete [] static_cast (p);
+ ::operator delete (p);
}
template void
ACE_Svc_Handler::destroy ()
@@ -78412,11 +78415,12 @@
if (this->mod_ == 0 && this->dynamic_ && this->closing_ == false)
delete this;
}
-template void
+template
+inline __attribute__ ((always_inline)) void
ACE_Svc_Handler::operator delete (void *obj)
{
;
- ::delete [] static_cast (obj);
+ ::operator delete (obj);
}
template
ACE_Svc_Handler::ACE_Svc_Handler
(ACE_Thread_Manager *tm,
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100406
[Bug 100406] bogus/missing -Wmismatched-new-delete
