[Bug c/103145] New: False positive of -Wstringop-overread on gcc-11

[Bug c/103145] New: False positive of -Wstringop-overread on gcc-11

[tonyfettes at tonyfettes dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103145

            Bug ID: 103145
           Summary: False positive of -Wstringop-overread on gcc-11
           Product: gcc
           Version: 11.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tonyfettes at tonyfettes dot com
  Target Milestone: ---

Hi,

The following piece of code will trigger -Wstringop-overread

$ cat test.c
// test.c
#include <stdio.h>

#define ARRAY_SIZE 4

struct func_in_t {
  int x;
  int y;
};

struct example_t {
  int field0;
  int field1;
  int field2;
  int field3;
  int field4;
};

struct example_t func(const struct func_in_t *in, const int array[ARRAY_SIZE])
{
  struct example_t out = {0};
  return out;
}

int main() {
  int array[ARRAY_SIZE] = { 0, 0, 0, 0 };
  struct func_in_t in = {
    .x = 0,
    .y = 0,
  };
  struct example_t col = func(&in, array);
  (void) col;
  return 0;
}

$ gcc -fno-strict-aliasing -fwrapv -Wall test.c -o test 
test.c: In function ‘main’:
test.c:30:26: warning: ‘func’ reading 16 bytes from a region of size 8
[-Wstringop-overread]
   30 |   struct example_t col = func(&in, array);
      |                          ^~~~~~~~~~~~~~~~
test.c:30:26: note: referencing argument 2 of type ‘const int *’
test.c:19:18: note: in a call to function ‘func’
   19 | struct example_t func(const struct func_in_t *in, const int
array[ARRAY_SIZE]) {
      |                  ^~~~

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-linux-gnu/11.1.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /build/gcc/src/gcc/configure --prefix=/usr --libdir=/usr/lib
--libexecdir=/usr/lib --mandir=/usr/share/man --infodir=/usr/share/info
--with-bugurl=https://bugs.archlinux.org/
--enable-languages=c,c++,ada,fortran,go,lto,objc,obj-c++,d --with-isl
--with-linker-hash-style=gnu --with-system-zlib --enable-__cxa_atexit
--enable-cet=auto --enable-checking=release --enable-clocale=gnu
--enable-default-pie --enable-default-ssp --enable-gnu-indirect-function
--enable-gnu-unique-object --enable-install-libiberty --enable-linker-build-id
--enable-lto --enable-multilib --enable-plugin --enable-shared
--enable-threads=posix --disable-libssp --disable-libstdcxx-pch
--disable-libunwind-exceptions --disable-werror
gdc_include_dir=/usr/include/dlang/gdc
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.1.0 (GCC) 

It seems like a duplication of
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101854, but I'm not sure about it
since gcc gave different diagnostics (one is overread, the other is overflow),
so I decide to submit it anyway.

[Bug tree-optimization/103145] False positive of -Wstringop-overread on gcc-11

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103145

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|                            |10.3.0, 12.0
             Blocks|                            |97048
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2021-11-09
      Known to fail|                            |11.2.0
     Ever confirmed|0                           |1

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
Confirmed with GCC 11.  It's fixed on trunk but at the moment I'm having
trouble finding the commit that fixed to see if it's suitable for backporting.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97048
[Bug 97048] [meta-bug] bogus/missing -Wstringop-overread warnings

[Bug tree-optimization/103145] [11 Regression] bogus -Wstringop-overread with an array argument

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103145

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|False positive of           |[11 Regression] bogus
                   |-Wstringop-overread on      |-Wstringop-overread with an
                   |gcc-11                      |array argument
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=102810

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
See also pr102810 for a similar looking problem (not yet fixed).

[Bug tree-optimization/103145] [11 Regression] bogus -Wstringop-overread with an array argument

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103145

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |needs-bisection
           Priority|P3                          |P2
   Target Milestone|---                         |11.3

[Bug tree-optimization/103145] [11 Regression] bogus -Wstringop-overread with an array argument

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103145

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|needs-bisection             |

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
The warning started with r11-3305 and went away with r12-2976

[Bug tree-optimization/103145] [11 Regression] bogus -Wstringop-overread with an array argument

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103145

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.3                        |11.4

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 11.3 is being released, retargeting bugs to GCC 11.4.

[Bug tree-optimization/103145] [11 Regression] bogus -Wstringop-overread with an array argument

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103145

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|11.4                        |11.5

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
GCC 11.4 is being released, retargeting bugs to GCC 11.5.