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

["tonyfettes at tonyfettes dot com" <gcc-bugzilla@gcc.gnu.org>]

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.