changlog entry

Author: jsinglet

cpp/change-notes/2021-06-10-std-types.md

@@ -0,0 +1,4 @@
+lgtm,codescanning
+* Added definitions for types found in `cstdint`. Added types `FixedWidthIntegralType`, `MinimumWidthIntegralType`, `FastestMinimumWidthIntegralType`, and `MaximumWidthIntegralType` to describe types such as `int8_t`, `int_least8_t`, `int_fast8_t`, and `intmax_t` respectively. 
+* Changed definition of `Intmax_t` and `Uintmax_t` to be part of the new type structure. 
+* Added a type `FixedWidthEnumType` which describes enums based on afixed-width integer type. For instance, `enum e: uint8_t = { a, b };`.