Protect base/numerics against change in intmax_t's underlying type

base/numerics/safe_math_impl.h

Index: base/numerics/safe_math_impl.h
diff --git a/base/numerics/safe_math_impl.h b/base/numerics/safe_math_impl.h
index 71fc278b297c26f7bf51ec695a3baacdb977e961..e6de6c85d5e338781aaeb5ef1070f0defca9a101 100644
--- a/base/numerics/safe_math_impl.h
+++ b/base/numerics/safe_math_impl.h
@@ -57,6 +57,8 @@ struct IntegerForSizeAndSign<8, true> {
 template <>
 struct IntegerForSizeAndSign<8, false> {
   typedef uint64_t type;
+  static_assert(sizeof(uintmax_t) == 8,

[Tom Sepez, 2016/11/17 17:04:54]

nit: Do you want a <= or >= comparison here?  Does the code break in both
directions?

[jschuh, 2016/11/17 18:06:46]

Good question. I can't really test, but I've seen enough implicit assumptions
that will break in the > case. And I figure it's safer to be strict than not,
assuming it makes it through the bots.

+                "Max integer size not supported for this toolchain.");
 };
 
 // WARNING: We have no IntegerForSizeAndSign<16, *>. If we ever add one to