[Bug c++/100309] New: [11 regression] false positive -Wstringop-overflow/stringop-overread/array-bounds on reinterpret_cast'd integers

[Bug c++/100309] New: [11 regression] false positive -Wstringop-overflow/stringop-overread/array-bounds on reinterpret_cast'd integers

[sciresm.gccbugzilla at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100309

            Bug ID: 100309
           Summary: [11 regression] false positive
                    -Wstringop-overflow/stringop-overread/array-bounds on
                    reinterpret_cast'd integers
           Product: gcc
           Version: 11.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sciresm.gccbugzilla at gmail dot com
  Target Milestone: ---

Created attachment 50697
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=50697&action=edit
Minimal test case code.

Bug occurs in GCC 11.1.0, but none of the 10.x releases.

It appears that GCC is now inferring a size of 0 when doing
reinterpret_cast<void*>(ConstantInteger); when doing std::memcpy/std::memset
to/from the result pointers, bogus warnings are emitted about reading/writing
to regions of zero size.

My target is an embedded system with a fixed memory layout; I have been using
constexpr uintptr_t/size_ts's to describe the memory regions, and
correspondingly calls to set or copy memory regions are now emitting bogus
warnings.

I have made an example minimal test case here (also attached):
https://godbolt.org/z/WPaGY8eaz

Relevant errors (compiling with -O -Werror):

void StringopOverread() {
    // error: 'void* memset(void*, int, size_t)' writing 16 bytes into a region
of size 0 overflows the destination [-Werror=stringop-overflow=]
    std::memset(reinterpret_cast<void *>(0xCAFEBABE), 0xCC, 0x10);
}

void StringopOverflow2(const void *src) {
    // error: 'void* memcpy(void*, const void*, size_t)' writing 16 bytes into
a region of size 0 overflows the destination [-Werror=stringop-overflow=]
    std::memcpy(reinterpret_cast<void *>(0xCAFEBABE), src, 0x10);
}

void StringopOverread(void *dst) {
    // error: 'void* memcpy(void*, const void*, size_t)' reading 16 bytes from
a region of size 0 [-Werror=stringop-overread]
    std::memcpy(dst, reinterpret_cast<void *>(0xCAFEBABE), 0x10);
}

[Bug c++/100309] [11 regression] false positive -Wstringop-overflow/stringop-overread/array-bounds on reinterpret_cast'd integers

[harald at gigawatt dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100309

Harald van Dijk <harald at gigawatt dot nl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |harald at gigawatt dot nl

--- Comment #1 from Harald van Dijk <harald at gigawatt dot nl> ---
This is a duplicate of bug 99578.

[Bug c++/100309] [11/12 regression] false positive -Wstringop-overflow/stringop-overread/array-bounds on reinterpret_cast'd integers

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100309

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
            Summary|[11 regression] false       |[11/12 regression] false
                   |positive                    |positive
                   |-Wstringop-overflow/stringo |-Wstringop-overflow/stringo
                   |p-overread/array-bounds on  |p-overread/array-bounds on
                   |reinterpret_cast'd integers |reinterpret_cast'd integers
   Target Milestone|---                         |11.2

[Bug middle-end/100309] [11/12 regression] false positive -Wstringop-overflow/stringop-overread/array-bounds on reinterpret_cast'd integers

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100309

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c++                         |middle-end
                 CC|                            |msebor at gcc dot gnu.org
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
Thus resolved as a dupe.

*** This bug has been marked as a duplicate of bug 99578 ***