On 22/07/2024 17:13, Joern Wolfgang Rennecke wrote:
> I guess you could reduce the differences between platforms if you
didn't
use types as defined by headerfiles directly, as they might be #defines
or typedefs or whatever, and instead used your own typedef or struct types.
It seems a typedef to int is seen through, even if you chain two of them
together.
After preprocessing, newlib has:
typedef long int __int32_t;
typedef __int32_t int32_t ;
So the crucial point seems to be to have 'long int', but that is of
course not portable for int32_t.
So to get portable code and consistent messages, I suppose we should use
a struct:
typedef struct { int32_t i; } my_int32;
my_int32 s42 = { 42 };
my_int32 *buf = (my_int32 *) __builtin_alloca (4 * size + 3); /* {
dg-warning "allocated buffer size is not a multiple of the pointee's
size" } */
buf[size] = s42; /* { dg-warning "stack-based buffer overflow" } */
Now suddenly the diagram is made *more* verbose, with the struct keyword
added.
┌─────────────────────────────────────────────┐
│ write of ‘struct my_int32’ (4 bytes) │
└─────────────────────────────────────────────┘
│ │
│ │
v v
┌───────────────────────────────────────┐ ┌────────────────────────┐
│ buffer allocated on stack at (1) │ │ after valid range │
└───────────────────────────────────────┘ └────────────────────────┘
├───────────────────┬───────────────────┤ ├───────────┬────────────┤
│ │
╭────────────────┴───────────────╮ ╭─────────┴────────╮
│capacity: ‘(size * 4) + 3’ bytes│ │overflow of 1 byte│
╰────────────────────────────────╯ ╰──────────────────╯
