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Este es un seguimiento de Critique my heap debugger de ayer. Como sugiere bitc, ahora guardo los metadatos sobre los bloques asignados en una tabla de claves manuscrita separada.Critica mi depurador de montón no intrusivo
El depurador montón ahora detecta los siguientes tipos de errores:
- pérdidas de memoria (ahora con salida de depuración más detallada)
- punteros ilegales pasaron a eliminar (que también se encarga de eliminaciones dobles)
- forma equivocada de borrado (matriz frente a no-array)
- desbordamientos de búfer
- búfer subdesborda
Siéntase libre de discutir y gracias de antemano!
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <new>
namespace
{
// I don't want to #include <algorithm> for a single function template :)
template <typename T>
void my_swap(T& x, T& y)
{
T z(x);
x = y;
y = z;
}
typedef unsigned char byte;
const byte CANARY[] = {0x5A, 0xFE, 0x6A, 0x8D,
0x5A, 0xFE, 0x6A, 0x8D,
0x5A, 0xFE, 0x6A, 0x8D,
0x5A, 0xFE, 0x6A, 0x8D};
bool canary_dead(const byte* cage)
{
bool dead = memcmp(cage, CANARY, sizeof CANARY);
if (dead)
{
for (size_t i = 0; i < sizeof CANARY; ++i)
{
byte b = cage[i];
printf(b == CANARY[i] ? "__ " : "%2X ", b);
}
putchar('\n');
}
return dead;
}
enum kind_of_memory {AVAILABLE, TOMBSTONE, NON_ARRAY_MEMORY, ARRAY_MEMORY};
const char* kind_string[] = {0, 0, "non-array memory", " array memory"};
struct metadata
{
byte* address;
size_t size;
kind_of_memory kind;
bool in_use() const
{
return kind & 2;
}
void print() const
{
printf("%s at %p (%d bytes)\n", kind_string[kind], address, size);
}
bool must_keep_searching_for(void* address)
{
return kind == TOMBSTONE || (in_use() && address != this->address);
}
bool canaries_alive() const
{
bool alive = true;
if (canary_dead(address - sizeof CANARY))
{
printf("ERROR: buffer underflow at %p\n", address);
alive = false;
}
if (canary_dead(address + size))
{
printf("ERROR: buffer overflow at %p\n", address);
alive = false;
}
return alive;
}
};
const size_t MINIMUM_CAPACITY = 11;
class hashtable
{
metadata* data;
size_t used;
size_t capacity;
size_t tombstones;
public:
size_t size() const
{
return used - tombstones;
}
void print() const
{
for (size_t i = 0; i < capacity; ++i)
{
if (data[i].in_use())
{
printf(":(leaked ");
data[i].print();
}
}
}
hashtable()
{
used = 0;
capacity = MINIMUM_CAPACITY;
data = static_cast<metadata*>(calloc(capacity, sizeof(metadata)));
tombstones = 0;
}
~hashtable()
{
free(data);
}
hashtable(const hashtable& that)
{
used = 0;
capacity = 3 * that.size() | 1;
if (capacity < MINIMUM_CAPACITY) capacity = MINIMUM_CAPACITY;
data = static_cast<metadata*>(calloc(capacity, sizeof(metadata)));
tombstones = 0;
for (size_t i = 0; i < that.capacity; ++i)
{
if (that.data[i].in_use())
{
insert_unsafe(that.data[i]);
}
}
}
hashtable& operator=(hashtable copy)
{
swap(copy);
return *this;
}
void swap(hashtable& that)
{
my_swap(data, that.data);
my_swap(used, that.used);
my_swap(capacity, that.capacity);
my_swap(tombstones, that.tombstones);
}
void insert_unsafe(const metadata& x)
{
*find(x.address) = x;
++used;
}
void insert(const metadata& x)
{
if (2 * used >= capacity)
{
hashtable copy(*this);
swap(copy);
}
insert_unsafe(x);
}
metadata* find(void* address)
{
size_t index = reinterpret_cast<size_t>(address) % capacity;
while (data[index].must_keep_searching_for(address))
{
++index;
if (index == capacity) index = 0;
}
return &data[index];
}
void erase(metadata* it)
{
it->kind = TOMBSTONE;
++tombstones;
}
} the_hashset;
struct heap_debugger
{
heap_debugger()
{
puts("heap debugger started");
}
~heap_debugger()
{
the_hashset.print();
puts("heap debugger shutting down");
}
} the_heap_debugger;
void* allocate(size_t size, kind_of_memory kind) throw (std::bad_alloc)
{
byte* raw = static_cast<byte*>(malloc(size + 2 * sizeof CANARY));
if (raw == 0) throw std::bad_alloc();
memcpy(raw, CANARY, sizeof CANARY);
byte* payload = raw + sizeof CANARY;
memcpy(payload + size, CANARY, sizeof CANARY);
metadata md = {payload, size, kind};
the_hashset.insert(md);
printf("allocated ");
md.print();
return payload;
}
void release(void* payload, kind_of_memory kind) throw()
{
if (payload == 0) return;
metadata* p = the_hashset.find(payload);
if (!p->in_use())
{
printf("ERROR: no dynamic memory at %p\n", payload);
}
else if (p->kind != kind)
{
printf("ERROR:wrong form of delete at %p\n", payload);
}
else if (p->canaries_alive())
{
printf("releasing ");
p->print();
free(static_cast<byte*>(payload) - sizeof CANARY);
the_hashset.erase(p);
}
}
}
void* operator new(size_t size) throw (std::bad_alloc)
{
return allocate(size, NON_ARRAY_MEMORY);
}
void* operator new[](size_t size) throw (std::bad_alloc)
{
return allocate(size, ARRAY_MEMORY);
}
void operator delete(void* payload) throw()
{
release(payload, NON_ARRAY_MEMORY);
}
void operator delete[](void* payload) throw()
{
release(payload, ARRAY_MEMORY);
}
int main()
{
int* p = new int[1];
delete p; // wrong form of delete
delete[] p; // ok
delete p; // no dynamic memory (double delete)
p = new int[1];
p[-1] = 0xcafebabe;
p[+1] = 0x12345678;
delete[] p; // underflow and overflow prevent release
// p is not released, hence leak
}
¿No podría haber editado la versión de ayer de esta pregunta en lugar de comenzar otra pregunta sobre el mismo tema? –
@Paul R: Este es completamente diferente ya que podría funcionar. – UncleBens
No utilice la especificación de excepción, simplemente ponga esto en comentario si quiere que la gente lo sepa :) –