The curse of char*
Whew! Finally I was able to solve the bug I was tring to fix in my game. To explain briefly, I have an std::map<char*, BITMAP*> which is a static member of a class. Now, I have a Manager class which loads resources that somehow looked like this
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| BITMAP* BitmapManager::addBitmap(char* key, char* fileName)
{
BITMAP* bitmap = load_bitmap(fileName, NULL);
bitmapTable.insert( std::pair<char*, BITMAP*>(key, bitmap) );
return bitmap;
}
BITMAP* BitmapManager::getBitmap(char* key)
{
std::map<char*, BITMAP*>::iterator it = bitmapTable.find(key);
BITMAP* bitmap = it->second;
return bitmap;
} |
As my code goes deeper and deeper and I pass a reference to a BITMAP by calling the BitmapManager's getBitmap function, I somehow encountered a situation when the pointer already became unreacheable and my program would crash when I make a call to BITMAP's(bitmap is a struct) w member which is equivalent to the bitmap width . The call to getBitmap would return NULL or 0.
Thanks to some guy in the allegro.cc forums who advised me to use std::string instead of char*. I don't know the exact reason why this would happen, but the solu worked anyway.
In the end, I didn't use a char* or std::string at all and just used an enum type(implicit integer) for my map key.
The final code look like this
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| BITMAP* BitmapManager::addBitmap(BitmapKeys key, char* fileName)
{
BITMAP* bitmap = load_bitmap(fileName, NULL);
bitmapTable.insert( std::pair<BitmapKeys, BITMAP*>(key, bitmap) );
return bitmap;
}
BITMAP* BitmapManager::getBitmap(BitmapKeys key)
{
std::map<BitmapKeys, BITMAP*>::iterator it = bitmapTable.find(key);
BITMAP* bitmap = it->second;
return bitmap;
} |