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Avoid overflowing the stack when allocating memory for polytope in EPA.

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PiperOrigin-RevId: 688641864
Change-Id: I3eef7e821ffbfa8d97a946ecf86d098cb4f0c233
This commit is contained in:
Kyle Bayes
2024-10-22 12:10:29 -07:00
committed by Copybara-Service
parent 4a3f77dd1f
commit 0c97dcf1fd
3 changed files with 35 additions and 7 deletions
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src/engine/engine_collision_gjk.c
+16 -5
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@@ -1327,16 +1327,27 @@ mjtNum mjc_ccd(const mjCCDConfig* config, mjCCDStatus* status, mjCCDObj* obj1, m
Polytope pt;
pt.nfaces = pt.nmap = pt.nverts = 0;
// allocate memory for faces
pt.maxfaces = (6*N > 1000) ? 6*N : 1000; // use 1000 faces as lower bound
pt.faces = mj_stackAllocByte(d, sizeof(Face) * pt.maxfaces, _Alignof(Face));
pt.map = mj_stackAllocByte(d, sizeof(Face*) * pt.maxfaces, _Alignof(Face*));
// allocate memory for vertices
pt.verts = mj_stackAllocNum(d, 3*(5 + N));
pt.verts1 = mj_stackAllocNum(d, 3*(5 + N));
pt.verts2 = mj_stackAllocNum(d, 3*(5 + N));
// allocate memory for faces
pt.maxfaces = (6*N > 1000) ? 6*N : 1000; // use 1000 faces as lower bound
size_t size1 = sizeof(Face) * pt.maxfaces;
size_t size2 = sizeof(Face*) * pt.maxfaces;
// since a generous upper bound is used, we need to rescale stack use if not enough
// memory is available
size_t max_size = mj_stackBytesAvailable(d) - 12*(N * sizeof(int));
if (size1 + size2 > max_size) {
pt.maxfaces = max_size / (sizeof(Face) + sizeof(Face*));
size1 = sizeof(Face) * pt.maxfaces;
size2 = sizeof(Face*) * pt.maxfaces;
}
pt.faces = mj_stackAllocByte(d, size1, _Alignof(Face));
pt.map = mj_stackAllocByte(d, size2, _Alignof(Face*));
int ret;
if (status->nsimplex == 2) {
ret = polytope2(&pt, status, obj1, obj2);