gccrs: add checks for division by zero and left shift overflow

These are ported from the c-family code c-warn.cc and c/c-typchk.cc

Fixes Rust-GCC#2394

gcc/rust/ChangeLog:

	* backend/rust-constexpr.cc (eval_store_expression): check for null
	(eval_call_expression): remove bad warning
	* rust-gcc.cc (arithmetic_or_logical_expression): add warnings

gcc/testsuite/ChangeLog:

	* rust/compile/issue-2394.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/gcc/rust/backend/rust-constexpr.cc b/gcc/rust/backend/rust-constexpr.cc
index bfd7d95..2f2bbbd 100644
--- a/gcc/rust/backend/rust-constexpr.cc
+++ b/gcc/rust/backend/rust-constexpr.cc
@@ -2929,8 +2929,13 @@ eval_store_expression (const constexpr_ctx *ctx, tree t, bool lval,
 	}
     }
 
+  if (*non_constant_p)
+    return t;
+
   /* Don't share a CONSTRUCTOR that might be changed later.  */
   init = unshare_constructor (init);
+  if (init == NULL_TREE)
+    return t;
 
   if (*valp && TREE_CODE (*valp) == CONSTRUCTOR
       && TREE_CODE (init) == CONSTRUCTOR)
@@ -3585,9 +3590,6 @@ eval_call_expression (const constexpr_ctx *ctx, tree t, bool lval,
 	      result = *ctx->global->values.get (res);
 	      if (result == NULL_TREE && !*non_constant_p)
 		{
-		  if (!ctx->quiet)
-		    error ("%<constexpr%> call flows off the end "
-			   "of the function");
 		  *non_constant_p = true;
 		}
 	    }