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Improve DynamicBVH code to make it clearer how the stack/heap works.

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Inspired by a Coverity issue about possible memcpy usage and overlapping memory.
This commit is contained in:
Alistair Leslie-Hughes 2023-11-17 12:53:31 +11:00
parent 41365c6c8b
commit 46531964d0
1 changed files with 12 additions and 6 deletions
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18
core/math/dynamic_bvh.h
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@ -328,7 +328,8 @@ void DynamicBVH::aabb_query(const AABB &p_box, QueryResult &r_result) {
volume.min = p_box.position; volume.min = p_box.position;
volume.max = p_box.position + p_box.size; volume.max = p_box.position + p_box.size;
const Node **stack = (const Node **)alloca(ALLOCA_STACK_SIZE * sizeof(const Node *)); const Node **alloca_stack = (const Node **)alloca(ALLOCA_STACK_SIZE * sizeof(const Node *));
const Node **stack = alloca_stack;
stack[0] = bvh_root; stack[0] = bvh_root;
int32_t depth = 1; int32_t depth = 1;
int32_t threshold = ALLOCA_STACK_SIZE - 2; int32_t threshold = ALLOCA_STACK_SIZE - 2;
@ -343,7 +344,8 @@ void DynamicBVH::aabb_query(const AABB &p_box, QueryResult &r_result) {
if (depth > threshold) { if (depth > threshold) {
if (aux_stack.is_empty()) { if (aux_stack.is_empty()) {
aux_stack.resize(ALLOCA_STACK_SIZE * 2); aux_stack.resize(ALLOCA_STACK_SIZE * 2);
memcpy(aux_stack.ptr(), stack, ALLOCA_STACK_SIZE * sizeof(const Node *)); memcpy(aux_stack.ptr(), alloca_stack, ALLOCA_STACK_SIZE * sizeof(const Node *));
alloca_stack = nullptr;
} else { } else {
aux_stack.resize(aux_stack.size() * 2); aux_stack.resize(aux_stack.size() * 2);
} }
@ -384,7 +386,8 @@ void DynamicBVH::convex_query(const Plane *p_planes, int p_plane_count, const Ve
} }
} }
const Node **stack = (const Node **)alloca(ALLOCA_STACK_SIZE * sizeof(const Node *)); const Node **alloca_stack = (const Node **)alloca(ALLOCA_STACK_SIZE * sizeof(const Node *));
const Node **stack = alloca_stack;
stack[0] = bvh_root; stack[0] = bvh_root;
int32_t depth = 1; int32_t depth = 1;
int32_t threshold = ALLOCA_STACK_SIZE - 2; int32_t threshold = ALLOCA_STACK_SIZE - 2;
@ -399,7 +402,8 @@ void DynamicBVH::convex_query(const Plane *p_planes, int p_plane_count, const Ve
if (depth > threshold) { if (depth > threshold) {
if (aux_stack.is_empty()) { if (aux_stack.is_empty()) {
aux_stack.resize(ALLOCA_STACK_SIZE * 2); aux_stack.resize(ALLOCA_STACK_SIZE * 2);
memcpy(aux_stack.ptr(), stack, ALLOCA_STACK_SIZE * sizeof(const Node *)); memcpy(aux_stack.ptr(), alloca_stack, ALLOCA_STACK_SIZE * sizeof(const Node *));
alloca_stack = nullptr;
} else { } else {
aux_stack.resize(aux_stack.size() * 2); aux_stack.resize(aux_stack.size() * 2);
} }
@ -436,7 +440,8 @@ void DynamicBVH::ray_query(const Vector3 &p_from, const Vector3 &p_to, QueryResu
Vector3 bounds[2]; Vector3 bounds[2];
const Node **stack = (const Node **)alloca(ALLOCA_STACK_SIZE * sizeof(const Node *)); const Node **alloca_stack = (const Node **)alloca(ALLOCA_STACK_SIZE * sizeof(const Node *));
const Node **stack = alloca_stack;
stack[0] = bvh_root; stack[0] = bvh_root;
int32_t depth = 1; int32_t depth = 1;
int32_t threshold = ALLOCA_STACK_SIZE - 2; int32_t threshold = ALLOCA_STACK_SIZE - 2;
@ -456,7 +461,8 @@ void DynamicBVH::ray_query(const Vector3 &p_from, const Vector3 &p_to, QueryResu
if (depth > threshold) { if (depth > threshold) {
if (aux_stack.is_empty()) { if (aux_stack.is_empty()) {
aux_stack.resize(ALLOCA_STACK_SIZE * 2); aux_stack.resize(ALLOCA_STACK_SIZE * 2);
memcpy(aux_stack.ptr(), stack, ALLOCA_STACK_SIZE * sizeof(const Node *)); memcpy(aux_stack.ptr(), alloca_stack, ALLOCA_STACK_SIZE * sizeof(const Node *));
alloca_stack = nullptr;
} else { } else {
aux_stack.resize(aux_stack.size() * 2); aux_stack.resize(aux_stack.size() * 2);
} }