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Code Issues Releases Wiki Activity

Use offsetof to reduce UB

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This commit is contained in:
Jesse Ruderman
2021-07-11 07:45:55 -07:00
parent cac0b57d7c
commit 98fd1f9c47
3 changed files with 4 additions and 4 deletions
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5
locations.cpp
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@@ -134,7 +134,7 @@ template<class T> struct connection_table {
unsigned char *spintable() { return (unsigned char*) (&move_table[full()->degree()]); }
/** \brief get the full T from the pointer to this connection table */
T* full() { T* x = (T*) this; return (T*)((char*)this - ((char*)(&(x->c)) - (char*)x)); }
T* full() { return (T*)((char*)this - offsetof(T, c)); }
/** \brief for the edge d, set the `spin` and `mirror` attributes */
void setspin(int d, int spin, bool mirror) {
unsigned char& c = spintable() [d];
@@ -178,10 +178,9 @@ template<class T> struct connection_table {
*/
template<class T> T* tailored_alloc(int degree) {
const T* sample = nullptr;
T* result;
#ifndef NO_TAILORED_ALLOC
int b = (char*)&sample->c.move_table[degree] + degree - (char*) sample;
int b = offsetof(T, c) + offsetof(connection_table<T>, move_table) + sizeof(T*) * degree + degree;
result = (T*) new char[b];
new (result) T();
#else