I'm using Visual studio 2005 to run some of company's C++ code on an emulator. This is a build with debug info enabled.
At a certain point I get a crash on a memcpy. My src pointer is a pointer to an offset on a memory mapped file. This address is calculated by our memory mapping code. Athe moment of the crash src = 0x3084f87a.
dst is a buffer big enough to hold the data we want to copy (6022 bytes).
The output gives me the following messages:
I know it seems like a open an shut case, but I fail to understand what's so special about the address.
First-chance exception at 0x023211ea in prog.exe: 0xC0000005: Access violation reading location 0x30850000.
Unhandled exception at 0x023211ea in prog.exe: 0xC0000005: Access violation reading location 0x30850000.
Below is a snapshot of memcpy.asm. Visual studio pointed to the line starting with 'rep'.
test edi,11b ;U - destination dword aligned?
jnz short CopyLeadUp ;V - if we are not dword aligned already, align
shr ecx,2 ;U - shift down to dword count
and edx,11b ;V - trailing byte count
cmp ecx,8 ;U - test if small enough for unwind copy
jb short CopyUnwindUp ;V - if so, then jump
rep movsd ;N - move all of our dwords
jmp dword ptr TrailUpVec[edx*4] ;N - process trailing bytes
If anyone can help me get some clarity into this I would appreciate it.