sanitisers-guide
dynamic-stack-buffer-overflow
A dynamic-stack-buffer-overflow occurs when you attempt to access memory outside a variable-length array (VLA). This is, an array that has been initialised as array[n] where n is a variable.
VLAs are allocated on the stack, since they are a local variable of the function. The “dynamic” is because, unlike all other local variables, the amount of memory needed for a VLA cannot be known at compile time. Hence, memory is dynamically allocated as needed.
Note: The COMP2521 style guide forbids using VLAs. Instead, you should dynamically allocate an array using malloc(). On top of the reasons listed in the style guide, it means anything that produces this error would instead produce a heap-buffer-overflow, which is significantly more descriptive.
Reading the error message
This is a typical dynamic-stack-buffer-overflow message:
Here is the useful information you can get from this error message:
Access Type
The blue line starts with READ/WRITE of size N.
Firstly, this tells us whether the error occurred due to reading from or writing to an invalid address. If you have a line like dest[i] = src[i] with both reading and writing, this can tell you whether the error is with reading from src or writing to dest.
This also gives some hints to the type of the memory you tried to access. For example if N=4 then we might be trying to access an integer which is 4 bytes.
Error Location
The first stack trace describes where (which line/function/file) the error occurred. See here for a guide on reading stack traces.