Implement variable length arrays

Variably modified types are required for C23.

Since QBE doesn't currently support saving and restoring the stack
pointer, a current limitation is that we can't reclaim stack space
from VLAs that go out of scope. This is potentially problematic for
VLAs appearing in a loop, but this case is uncommon enough that it
is silently ignored for now.

Implements: https://todo.sr.ht/~mcf/cproc/1
References: https://todo.sr.ht/~mcf/cproc/88
Co-authored-by: Michael Forney <mforney@mforney.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/test/vla.c b/test/vla.c
new file mode 100644
index 0000000..61f3dcf
--- /dev/null
+++ b/test/vla.c
@@ -0,0 +1,5 @@
+short g() { return 1; }
+long f(void) {
+    double a[10 + g()];
+    return sizeof(a);
+}