mem_t: Throw an error if zero-sized memory is requested (#168)

* mem_t: Throw an error if zero-sized memory is requested

If for some reason the user requests a memory size of 0 megabytes, print
a useful error message.

* Check for overflow in memory size

If the user passes in a large enough memory size (-m) that the size in
bytes doesn't fit into size_t, catch this error in the make_mems function.

1 files changed, 2 insertions, 0 deletions

diff --git a/riscv/devices.h b/riscv/devices.h
index e4df6c9..4e4d27f 100644
--- a/riscv/devices.h
+++ b/riscv/devices.h
@@ -41,6 +41,8 @@ class rom_device_t : public abstract_device_t {
 class mem_t : public abstract_device_t {
  public:
   mem_t(size_t size) : len(size) {
+    if (!size)
+      throw std::runtime_error("zero bytes of target memory requested");
     data = (char*)calloc(1, size);
     if (!data)
       throw std::runtime_error("couldn't allocate " + std::to_string(size) + " bytes of target memory");