add more details

1 files changed, 23 insertions, 1 deletions

diff --git a/safety.md b/safety.md
index d353227..6550492 100644
--- a/safety.md
+++ b/safety.md
@@ -4,7 +4,29 @@ Each item in Wikipedia's [list of types of memory errors](https://en.wikipedia.o
 

 ## Buffer overflow

 

-bounds checking based on uhhhh something

+Crowbar addresses buffer overflow with bounds checking.

+In C, the type `char *` can point to a single character, a null-terminated string of unknown length, a buffer of fixed size, or nothing at all.

+In Crowbar, the type `char *` can only point to either a single character or nothing at all.

+If a buffer is declared as `char[50] name;` then it has type `char[50]`, and can be implicitly converted to `(char[50])*`, a pointer-to-50-chars.

+If memory is dynamically allocated, it works as follows:

+

+```crowbar

+void process(size_t bufferSize, char[bufferSize] buffer) {

+    // do some work with buffer, given that we know its size

+}

+

+int main(int argc, (char[1024?])[argc] argv) {

+    size_t bufferSize = getBufferSize();

+    (char[bufferSize])* buffer = malloc(bufferSize);

+    process(bufferSize, buffer);

+    free(buffer);

+}

+```

+

+Note that `malloc` as part of the Crowbar standard library has signature `(char[size])* malloc(size_t size);` and so no cast is needed above.

+Note as well that the type of `argv` is complicated.

+This is because the elements of `argv` have unconstrained size.

+TODO figure out if that's the right way to handle that

 

 ## Buffer over-read