Changes in src/Helpers/MemDebug.cpp [28c351:68f03d]

File:

• src/Helpers/MemDebug.cpp (modified) (10 diffs)

src/Helpers/MemDebug.cpp

@@ -13 +13 @@
 
 namespace Memory {
+
+  // This struct is added before each memory chunk
+  // and contains tracking information. Anything used
+  // to track memory cannot use any dynamic memory, so
+  // we have to resort to classic C-idioms here.
+  // This struct also contains pointers to the next
+  // an previous chunks to allow fast traversion of
+  // all allocated memory blocks
   struct entry_t {
+    // we seperate the tracking info from the rest
+    // A checksum will be calculated for this part of
+    // the struct, so the information in here should
+    // not change during the lifetime of the memory
     struct info_t {
-      char file[256];
+      enum {length = 64};
+      char file[length+1];
       int line;
       size_t nbytes;
@@ -27 +40 @@
   };
 
+  // start and end of the doubly-linked list
   entry_t *begin=0;
   entry_t *end=0;
 
+  // current amount of allocated memory
   size_t state = 0;
+  // maximum amount of allocated memory
   size_t max = 0;
-
+  // number of allocations that have been done so far
+  unsigned int allocs = 0;
+
+
+  // this sets the alignment of the returned memory block
+  // malloc guarantees an alignment at the 8 byte border,
+  // so we just do the same
   const int alignment = 8;
 
+  // calculates a simple checksum for the info block
+  // the checksum is used to find memory corruptions
   inline char calcChecksum(entry_t::info_t *info){
     char *buffer = (char*)info;
@@ -44 +68 @@
   }
 
+  // gets the next alignet point which is greater than nbytes
+  // this function is only called a fixed number of times, so
+  // there is no need to optimize
   inline size_t doAlign(size_t nbytes){
     int nonaligned = nbytes % alignment;
@@ -54 +81 @@
   }
 
+  // Output some state information
   void getState(){
     cout << "Maximum allocated Memory: " << max << " bytes" << endl;
     cout << "Currently allocated Memory: " << state <<" bytes" << endl;
-
+    cout << allocs << " allocated chunks total" << endl;
+
+    // simple traversal of the chunk list
     for(entry_t *pos=begin;pos;pos=pos->next){
       cout << "\nChunk of " << pos->info.nbytes << " bytes" << " still available" << endl;
@@ -64 +94 @@
   }
 
+  // Deletes an entry from the linked list
   void deleteEntry(entry_t *entry){
     if(entry->isIgnored)
       return;
+
     if(entry->prev){
       entry->prev->next = entry->next;
     }
     else{
+      // this node was the beginning of the list
       begin = entry->next;
     }
@@ -78 +111 @@
     }
     else{
+      // this node was the end of the list
       end = entry->prev;
     }
@@ -85 +119 @@
 
   void _ignore(void *ptr){
+    // just deletes the node from the list, but leaves the info intact
     static const size_t entrySpace = Memory::doAlign(sizeof(Memory::entry_t));
     entry_t *entry = (Memory::entry_t*)((char*)ptr-entrySpace);
@@ -93 +128 @@
 void *operator new(size_t nbytes,const char* file, int line) throw(std::bad_alloc) {
 
+  // to avoid allocations of 0 bytes if someone screws up
+  // allocation with 0 byte size are undefined behavior, so we are
+  // free to handle it this way
   if(!nbytes) {
     nbytes = 1;
   }
 
+  // get the size of the entry, including alignment
   static const size_t entrySpace = Memory::doAlign(sizeof(Memory::entry_t));
 
   void *res;
   if(!(res=malloc(entrySpace + nbytes))){
+    // new must throw, when space is low
     throw std::bad_alloc();
   }
 
+  // we got the space, so update the global info
   Memory::state += nbytes;
   if(Memory::state>Memory::max){
     Memory::max = Memory::state;
   }
-
+  Memory::allocs++;
+
+  // build the entry in front of the space
   Memory::entry_t *entry = (Memory::entry_t*) res;
+  memset(res,0,entrySpace);
   entry->info.nbytes = nbytes;
   entry->info.isUsed = true;
-  strncpy(entry->info.file,file,256);
-  entry->info.file[255] = '\0';
+  strncpy(entry->info.file,file,Memory::entry_t::info_t::length);
+  entry->info.file[Memory::entry_t::info_t::length] = '\0';
   entry->info.line=line;
+  // the space starts behind the info
   entry->info.location = (char*)res + entrySpace;
 
-  entry->next=0;
-  entry->prev=Memory::end;
+  // add the entry at the end of the list
+  entry->next=0;            // the created block is last in the list
+  entry->prev=Memory::end;  // the created block is last in the list
   if(!Memory::begin){
+    // the list was empty... start a new one
     Memory::begin=entry;
   }
   else {
+    // other blocks present... we can add to the last one
     Memory::end->next=entry;
   }
   Memory::end=entry;
 
+  // get the checksum...
   entry->checksum = Memory::calcChecksum(&entry->info);
+  // this will be set to true, when the block is removed from
+  // the list for any reason
   entry->isIgnored = false;
 
+  // ok, space is prepared... the user can have it.
+  // the rest (constructor, deleting when something is thrown etc)
+  // is handled automatically
   return entry->info.location;
 }
 
 void *operator new(size_t nbytes) throw(std::bad_alloc) {
+  // Just forward to the other operator, when we do not know from
+  // where the allocation came
   return operator new(nbytes,"Unknown",0);
 }
 
 void *operator new[] (size_t nbytes,const char* file, int line) throw(std::bad_alloc) {
+  // The difference between new and new[] is just for compiler bookkeeping.
   return operator new(nbytes,file,line);
 }
 
 void *operator new[] (size_t nbytes) throw(std::bad_alloc) {
+  // Forward again
   return operator new[] (nbytes,"Unknown",0);
 }
 
 void operator delete(void *ptr) throw() {
+  // get the size for the entry, including alignment
   static const size_t entrySpace = Memory::doAlign(sizeof(Memory::entry_t));
 
+  // get the position for the entry from the pointer the user gave us
   Memory::entry_t *entry = (Memory::entry_t*)((char*)ptr-entrySpace);
 
+  // let's see if the checksum is still matching
   if(Memory::calcChecksum(&entry->info)!=entry->checksum){
     cout << "Possible memory corruption detected!" << endl;
@@ -157 +218 @@
   }
 
+  // this will destroy the checksum, so double deletes are caught
   entry->info.isUsed = false;
   Memory::deleteEntry(entry);
 
+  // delete the space reserved by malloc
   free((char*)ptr-entrySpace);
 }
 
+// operator that is called when the constructor throws
+// do not call manually
 void operator delete(void *ptr,const char*, int) throw() {
   operator delete(ptr);
@@ -168 +233 @@
 
 void operator delete[](void *ptr){
+  // again difference between delete and delete[] is just in compiler bookkeeping
   operator delete(ptr);
 }
 
+// and another operator that can be called when a constructor throws
 void operator delete[](void *ptr,const char*, int) throw(){
   operator delete(ptr);