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Integer Overflow Offensive, First Act: rintersect, hitscan, neartag.

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It's time to replace some int32s with 64-bit ints in core engine functions.
The problem is that for example, the dot product is taken between vectors that
may be the difference between two arbitrary points in a sector, so even if one
sticks to the "no blue walls" rule, that doesn't guarantee freedom from
overflows.

git-svn-id: https://svn.eduke32.com/eduke32@2761 1a8010ca-5511-0410-912e-c29ae57300e0
This commit is contained in:
helixhorned 2012-06-13 23:13:39 +00:00
parent 41921e728c
commit b30ac41147
1 changed files with 15 additions and 10 deletions
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25
polymer/eduke32/build/src/engine.c
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@ -7749,11 +7749,13 @@ int32_t lineintersect(int32_t x1, int32_t y1, int32_t z1, int32_t x2, int32_t y2
//
// rintersect (internal)
//
static int32_t rintersect(int32_t x1, int32_t y1, int32_t z1, int32_t vx, int32_t vy, int32_t vz, int32_t x3,
int32_t y3, int32_t x4, int32_t y4, int32_t *intx, int32_t *inty, int32_t *intz)
static int32_t rintersect(int32_t x1, int32_t y1, int32_t z1, int32_t vx_, int32_t vy_, int32_t vz, int32_t x3,
int32_t y3, int32_t x4, int32_t y4, int32_t *intx, int32_t *inty, int32_t *intz)
{
//p1 towards p2 is a ray
int32_t x34, y34, x31, y31, bot, topt, topu, t;
int64_t x34, y34, x31, y31, bot, topt, topu, t;
const int64_t vx=vx_, vy=vy_;
x34 = x3-x4; y34 = y3-y4;
bot = vx*y34 - vy*x34;
@ -7770,10 +7772,12 @@ static int32_t rintersect(int32_t x1, int32_t y1, int32_t z1, int32_t vx, int32_
topt = x31*y34 - y31*x34; if (topt > 0) return(0);
topu = vx*y31 - vy*x31; if ((topu > 0) || (topu <= bot)) return(0);
}
t = divscale16(topt,bot);
*intx = x1 + mulscale16(vx,t);
*inty = y1 + mulscale16(vy,t);
*intz = z1 + mulscale16(vz,t);
t = (topt<<16)/bot;
*intx = x1 + ((vx*t)>>16);
*inty = y1 + ((vy*t)>>16);
*intz = z1 + ((vz*t)>>16);
return(1);
}
@ -11012,6 +11016,7 @@ restart_grand:
y31 = wal->y-y1; y34 = wal->y-wal2->y;
bot = y21*x34-x21*y34; if (bot <= 0) continue;
// XXX: OVERFLOW
t = y21*x31-x21*y31; if ((unsigned)t >= (unsigned)bot) continue;
t = y31*x34-x31*y34;
if ((unsigned)t >= (unsigned)bot)
@ -11326,7 +11331,7 @@ restart_grand:
wal2 = &wall[wal->point2];
x1 = wal->x; y1 = wal->y; x2 = wal2->x; y2 = wal2->y;
if ((x1-sv->x)*(y2-sv->y) < (x2-sv->x)*(y1-sv->y)) continue;
if ((int64_t)(x1-sv->x)*(y2-sv->y) < (int64_t)(x2-sv->x)*(y1-sv->y)) continue;
if (rintersect(sv->x,sv->y,sv->z, vx,vy,vz, x1,y1, x2,y2, &intx,&inty,&intz) == 0) continue;
if (klabs(intx-sv->x)+klabs(inty-sv->y) >= klabs((hitinfo->pos.x)-sv->x)+klabs((hitinfo->pos.y)-sv->y))
@ -11442,7 +11447,7 @@ restart_grand:
y1 -= mulscale16(day,k); y2 = y1+mulscale16(day,l);
if ((cstat&64) != 0) //back side of 1-way sprite
if ((x1-sv->x)*(y2-sv->y) < (x2-sv->x)*(y1-sv->y)) continue;
if ((int64_t)(x1-sv->x)*(y2-sv->y) < (int64_t)(x2-sv->x)*(y1-sv->y)) continue;
if (rintersect(sv->x,sv->y,sv->z,vx,vy,vz,x1,y1,x2,y2,&intx,&inty,&intz) == 0) continue;
@ -11632,7 +11637,7 @@ void neartag(int32_t xs, int32_t ys, int32_t zs, int16_t sectnum, int16_t ange,
if ((tagsearch&2) && wal->hitag) good |= 2;
if ((good == 0) && (nextsector < 0)) continue;
if ((x1-xs)*(y2-ys) < (x2-xs)*(y1-ys)) continue;
if ((int64_t)(x1-xs)*(y2-ys) < (int64_t)(x2-xs)*(y1-ys)) continue;
if (lintersect(xs,ys,zs,xe,ye,ze,x1,y1,x2,y2,&intx,&inty,&intz) == 1)
{