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/spike_main/spike.cc b/spike_main/spike.cc
index 1205965..d3caa22 100644
--- a/spike_main/spike.cc
+++ b/spike_main/spike.cc
@@ -47,6 +47,8 @@ static std::vector<std::pair<reg_t, mem_t*>> make_mems(const char* arg)
   auto mb = strtoull(arg, &p, 0);
   if (*p == 0) {
     reg_t size = reg_t(mb) << 20;
+    if (size != (size_t)size)
+      throw std::runtime_error("Size would overflow size_t");
     return std::vector<std::pair<reg_t, mem_t*>>(1, std::make_pair(reg_t(DRAM_BASE), new mem_t(size)));
   }