From 489469a7b6668bcf27362896f7a9ed4bc2a99de1 Mon Sep 17 00:00:00 2001 From: Melody Horn Date: Tue, 20 Oct 2020 10:49:44 -0600 Subject: add detail on C VLAs --- safety.md | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'safety.md') diff --git a/safety.md b/safety.md index 6550492..271edc1 100644 --- a/safety.md +++ b/safety.md @@ -23,7 +23,11 @@ int main(int argc, (char[1024?])[argc] argv) { } ``` -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 that `malloc` as part of the Crowbar standard library has signature `(void[size])* malloc(size_t size);` and so no cast is needed above. +In C, `buffer` in `main` would have type pointer-to-VLA-of-char, but `buffer` in `process` would have type VLA-of-char, and this conversion would emit a compiler warning. +However, in Crowbar, a `(T[N])*` is always implicitly convertible to `T[N]`, so no warning exists. +(This is translated into C by dereferencing `buffer` in `main`.) + 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 -- cgit v1.2.3