[Bug middle-end/98483] New: missing -Warray-bounds for out of bounds accesses in system headers

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98483

            Bug ID: 98483
           Summary: missing -Warray-bounds for out of bounds accesses in
                    system headers
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: msebor at gcc dot gnu.org
  Target Milestone: ---

GCC warns for out-of-bounds accesses by inlined functions but not when they are
defined in system headers, even if the function is inlined into (and the
accessed object defined in) an ordinary, non-systen function.  This is
especially bad for C++ system libraries that are full of inline code.

$ cat b.c && gcc -O2 -S -Wall -fdump-tree-optimized=/dev/stdout b.c
# 1 "a.h" 1 3 4
# 2 "a.h" 3 4
static inline void f (int *p)
{
  *p = 0;
}

# 1 "b.c" 1

static inline void g (int *p)
{
  *p = 1;
}

int i[1];

void ff (void)
{
  f (i + 1);   // missing warning
}

void gg (void)
{
  g (i + 1);   // warning (good)
}


;; Function ff (ff, funcdef_no=2, decl_uid=1950, cgraph_uid=3, symbol_order=3)

void ff ()
{
  <bb 2> [local count: 1073741824]:
  MEM[(int *)&i + 4B] = 0;
  return;

}


In file included from a.h:7,
                 from b.c:1:
b.c: In function ‘gg’:
b.c:4:6: warning: array subscript 1 is outside array bounds of ‘int[1]’
[-Warray-bounds]
    4 | {
      |      ^  
b.c:7:5: note: while referencing ‘i’
    7 | 
      |     ^

;; Function gg (gg, funcdef_no=3, decl_uid=1953, cgraph_uid=4, symbol_order=4)

void gg ()
{
  <bb 2> [local count: 1073741824]:
  MEM[(int *)&i + 4B] = 1;
  return;

}