Crashes on mvdsv 0.32

[drzel]

12:40 AM] drzel: hey @meag I'm really hoping to upgrade my server to 0.32 if possible, is there anything else I can do re: QW-Group/mvdsv#34 ?
GitHub
Server dying after about 90 seconds · Issue #34 · deurk/mvdsv
Hey I'm running 0.31 fine at qw://fortressone.ga Compiled 0.32 and swapped out the binary and the server crashes after about 90 seconds with: sv_error: Program error At least that's what I ...

[12:41 AM] meag: are you compiling it with the same flags etc as you compiled 0.31?
[1:16 AM] Spoike: @drzel which qcc are you using?
[1:18 AM] Spoike: I'm assuming its frikqcc
[1:21 AM] Spoike: frikqcc (when using -O3 or whatever it was) also enables a 'logic-ops' optimisation.
[1:21 AM] Spoike: this allows it to short-circuit conditionals in an attempt to avoid needing to evaluate expensive expressions (like function calls)
[1:23 AM] Spoike: it does this by using OP_IF/OP_IFNOT directly on the lhs of any && or || operators so that it can just skip over the logic needed for the rhs+dependant operations etc
[1:24 AM] Spoike: unfortunately, those two instructions expressely operate only on ints and not floats.
[1:25 AM] Spoike: this means that (-0.0 && -0.0) suddenly ends up considered as true, instead of false.(edited)
[1:26 AM] Spoike: bitwise, -0.0 == 0x80000000, so true
[1:27 AM] Spoike: unfortunately whether a float is 0 or not is more complicated than just testing the non-sign bits.
[1:28 AM] Spoike: not all cpus support denormalised floats for instance, and normally handle them as if they're 0 (this can be a potentially significant speedup for intel cpus for instance).
[1:29 AM] Spoike: so yeah, disable that optimisation or rewrite the qc so that it doesn't matter so much
[1:34 AM] drzel: Hrmmm honestly a lot of that has gone over my head. I’m compiling with gmqcc -std=gmqcc -fftepp @meag
[1:36 AM] drzel: I’m in bed now but really appreciate the explanation. I’ll pore over it tomorrow
[4:36 AM] Spoike: oh, I'm sure gmqcc works well enough with DP, but you're not using DP.
[5:49 AM] Spoike: you could try changing your player_run line to if not(self.velocity_x || self.velocity_y) (the not there actually being hexenc syntax). I assume that'll be understood by gmqcc too, and should ensure both places use the exact same early-out logic (thus fixing the issue), as well as being a smidge faster (not that two opcodes difference is all that significant).
[5:49 AM] Spoike: but if you have any similar cases in your code, you'll have to find+fix those too.
[7:20 PM] drzel: Oh wow that's awesome, I'll look at that thanks @spoike
[9:26 PM] drzel: So just to clarify @spoike, you're saying that the reason the server is dying on mvdsv 0.32, but not 0.31 might be resolved by either:

• compiling qwprogs.dat with frikqcc, or
• changing if (!self.velocity_x && !self.velocity_y) to if not(self.velocity_x || self.velocity_y) and anywhere else that might end up with float && float?

[lordee]

fixed?

[drzel]

Fixed