Fix incorrectly parsed value of gid with horizontal flip flag on

[IoriBranford]

No description provided.

[baylej]

Hi, thank you for this,

What is the issue? I can't infer what it is from the contributed code.

Thanks!

[IoriBranford]

Gids in TMX files are unsigned int numbers, but atoi is only designed to read numbers in signed int range.
Ints nowadays have pretty much standardized to 32 bits, so a gid with the h-flip flag (the 32nd bit) is outside of signed int range. atoi doesn't handle this well and returns some incorrect value.

[baylej]

Thanks again, would using function atol() then downcasting to a uint32_t be a simpler alternative, wdyt?

[IoriBranford]

I decided on strtoull

• Returns 0 on non-number value, fortunately 0 is never a valid gid for a tile object.
• long long is almost always 64 bits while long may be 32 or 64. Thus we can tell if the value is beyond 32-bit range, whereas strtoul and atol would just return the max 32-bit value, which is still a valid gid (but the wrong one).

And also made content.gid unsigned, to be consistent with tmx format which stores gids as unsigned (e.g. gid 1 with h-flip is 2,147,483,649 instead of -2,147,483,647). It shouldn't break anything unless a user is silly and checks for h-flip with gid < 0.

[baylej]

Thanks for doing the change.

I don't understand why strtoul() wont work here, as an unsigned int certainly fits in an unsigned long 🤔
And in Tiled, tile ids are stored in 32 bits unsigned integers anyway

could you please detail your reasoning here?
Thanks

[IoriBranford]

strtoul can work, but does add an extra step when checking for out of gid range.

unsigned long gid = strtoul(value, NULL, 0);
if (gid > UINT_MAX || gid == ULONG_MAX && errno == ERANGE)
// Some systems have int and long as the same size.
// In that case you can't tell out-of-range from the value alone, and need to check errno.

vs

unsigned long long gid = strtoull(value, NULL, 0);
if (gid > UINT_MAX)