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Fix for benign UBsan signed-integer-overflow complaints.

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When counting nl and nc, the nnz is optionally also counted when in sparse mode. However, the functions mj_nl and mj_nc unconditionally counts nnz into a temporary accumulator, then only afterwards check whether the output nnz pointer is NULL.

When not in sparse mode, ten_J_rownnz does not get initialized by mj_tendon, however mj_nl and mj_nc are accumulating potentially spurious data from ten_J_rownnz into the temporary accumulator. While the spurious result eventually gets discarded, UBsan nevertheless detects an integer overflow in the temporary accumulator.

PiperOrigin-RevId: 662443910
Change-Id: I78a9a088d4db7f16be779c7d669167d6fb3e4401
This commit is contained in:
Saran Tunyasuvunakool
2024-08-13 03:07:48 -07:00
committed by Copybara-Service
parent e3814be8e6
commit 1132632627
1 changed files with 7 additions and 14 deletions
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src/engine/engine_core_constraint.c
+7 -14
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@@ -1706,7 +1706,7 @@ static int mj_ne(const mjModel* m, mjData* d, int* nnz) {
// count frictional constraints, count Jacobian nonzeros if nnz is not NULL
static int mj_nf(const mjModel* m, const mjData* d, int *nnz) {
int nf = 0, nnzf = 0;
int nf = 0;
int nv = m->nv, ntendon = m->ntendon;
if (mjDISABLED(mjDSBL_FRICTIONLOSS)) {
@@ -1716,21 +1716,17 @@ static int mj_nf(const mjModel* m, const mjData* d, int *nnz) {
for (int i=0; i < nv; i++) {
if (m->dof_frictionloss[i] > 0) {
nf += mj_addConstraintCount(m, 1, 1);
nnzf++;
if (nnz) *nnz += 1;
}
}
for (int i=0; i < ntendon; i++) {
if (m->tendon_frictionloss[i] > 0) {
nf += mj_addConstraintCount(m, 1, d->ten_J_rownnz[i]);
nnzf += d->ten_J_rownnz[i];
if (nnz) *nnz += d->ten_J_rownnz[i];
}
}
if (nnz) {
*nnz += nnzf;
}
return nf;
}
@@ -1738,7 +1734,7 @@ static int mj_nf(const mjModel* m, const mjData* d, int *nnz) {
// count limit constraints, count Jacobian nonzeros if nnz is not NULL
static int mj_nl(const mjModel* m, const mjData* d, int *nnz) {
int nnzl = 0, nl = 0;
int nl = 0;
int ntendon = m->ntendon;
int side;
mjtNum margin, value, dist;
@@ -1763,7 +1759,7 @@ static int mj_nl(const mjModel* m, const mjData* d, int *nnz) {
dist = side * (m->jnt_range[2*i+(side+1)/2] - value);
if (dist < margin) {
nl += mj_addConstraintCount(m, 1, 1);
nnzl++;
if (nnz) *nnz += 1;
}
}
}
@@ -1777,7 +1773,7 @@ static int mj_nl(const mjModel* m, const mjData* d, int *nnz) {
dist = mju_max(m->jnt_range[2*i], m->jnt_range[2*i+1]) - value;
if (dist < margin) {
nl += mj_addConstraintCount(m, 1, 3);
nnzl += 3;
if (nnz) *nnz += 3;
}
}
}
@@ -1792,15 +1788,12 @@ static int mj_nl(const mjModel* m, const mjData* d, int *nnz) {
dist = side * (m->tendon_range[2*i+(side+1)/2] - value);
if (dist < margin) {
nl += mj_addConstraintCount(m, 1, d->ten_J_rownnz[i]);
nnzl += d->ten_J_rownnz[i];
if (nnz) *nnz += d->ten_J_rownnz[i];
}
}
}
}
if (nnz) {
*nnz += nnzl;
}
return nl;
}