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enum { BLOCKSIZEBLOCK_HEADER_SIZE = 16 };
unsigned long long max = UINT_MAX;
void *AllocateBlock(size_t length) {
struct memBlock *mBlock;
if (length + BLOCK_HEADER_SIZE > max) return NULL;
mBlock = malloc(length + BLOCK_HEADER_SIZE);
if (!mBlock) return NULL;
/* fill in block header and return data portion */
return mBlock;
}
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enum { BLOCKSIZEBLOCK_HEADER_SIZE = 16 };
unsigned long long max = UINT_MAX;
void *AllocateBlock(size_t length) {
struct memBlock *mBlock;
if ((unsigned long long)length + BLOCK_HEADER_SIZE > max) return NULL;
mBlock = malloc(length + BLOCK_HEADER_SIZE);
if (!mBlock) return NULL;
/* fill in block header and return data portion */
return mBlock;
}
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In this non-compliant code example, the programmer attempts to prevent integer overflow by allocating an unsigned long long integer called alloc and assigning it the result from cBlocks * 16.
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enum { BLOCKSIZE = 16 };
unsigned long long max = UINT_MAX;
...
void* AllocBlocks(size_t cBlocks) {
if (cBlocks == 0) return NULL;
unsigned long long alloc = cBlocks * 16;
return (alloc < UINT_MAX) ? malloc(cBlocks * 16) : NULL;
}
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