[Bug middle-end/97027] missing warning on buffer overflow storing a larger scalar into a smaller array

[msebor at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97027

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
Another test case.  Of the buffer overflow in the four functions in it, only a
subset is diagnosed.  The subset depends on the form of the assignment in the
IL which in turn changes from target to target.  The output below is for
aarch64 which is different for x86_64.

$ cat xx.c && gcc -O2 -S -fdump-tree-optimized=/dev/stdout xx.c
void f16 (char c)
{
  typedef __attribute__ ((__vector_size__ (16))) char C16;

  extern char a16[16];
  void *p = a16 + 1;
  *(C16*)p = (C16){ c };
}

void f32 (char c)
{
  typedef __attribute__ ((__vector_size__ (32))) char C32;

  extern char a32[32];
  void *p = a32 + 1;
  *(C32*)p = (C32){ c };
}

void f64 (char c)
{
  typedef __attribute__ ((__vector_size__ (64))) char C64;

  extern char a64[64];
  void *p = a64 + 1;
  *(C64*)p = (C64){ c };
}

void f128 (char c)
{
  typedef __attribute__ ((__vector_size__ (128))) char C128;

  extern char a128[128];
  void *p = a128 + 1;
  *(C128*)p = (C128){ c };
}


;; Function f16 (f16, funcdef_no=0, decl_uid=3585, cgraph_uid=1,
symbol_order=0)

f16 (char c)
{
  vector(16) char _1;

  <bb 2> [local count: 1073741824]:
  _1 = {c_2(D)};
  MEM[(C16 *)&a16 + 1B] = _1;
  return;

}



;; Function f32 (f32, funcdef_no=1, decl_uid=3593, cgraph_uid=2,
symbol_order=1)

f32 (char c)
{
  vector(32) char _1;

  <bb 2> [local count: 1073741824]:
  _1 = {c_2(D)};
  MEM[(C32 *)&a32 + 1B] = _1;
  return;

}



;; Function f64 (f64, funcdef_no=2, decl_uid=3601, cgraph_uid=3,
symbol_order=2)

f64 (char c)
{
  vector(64) char _1;

  <bb 2> [local count: 1073741824]:
  _1 = {c_2(D)};
  MEM[(C64 *)&a64 + 1B] = _1;
  return;

}


xx.c: In function 'f128':
xx.c:34:13: warning: writing 1 byte into a region of size 0
[-Wstringop-overflow=]
   34 |   *(C128*)p = (C128){ c };
      |   ~~~~~~~~~~^~~~~~~~~~~~~
xx.c:32:15: note: at offset 128 to object 'a128' with size 128 declared here
   32 |   extern char a128[128];
      |               ^~~~

;; Function f128 (f128, funcdef_no=3, decl_uid=3609, cgraph_uid=4,
symbol_order=3)

f128 (char c)
{
  <bb 2> [local count: 1073741824]:
  BIT_FIELD_REF <MEM[(C128 *)&a128 + 1B], 8, 0> = c_2(D);
  MEM <unsigned long> [(C128 *)&a128 + 2B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 10B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 18B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 26B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 34B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 42B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 50B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 58B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 66B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 74B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 82B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 90B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 98B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 106B] = 0;
  MEM <unsigned long> [(C128 *)&a128 + 114B] = 0;
  MEM <unsigned int> [(C128 *)&a128 + 122B] = 0;
  MEM <unsigned short> [(C128 *)&a128 + 126B] = 0;
  BIT_FIELD_REF <MEM[(C128 *)&a128 + 1B], 8, 1016> = 0;
  return;

}