On Mon, 29 Jun 2020, Erick Ochoa wrote: > We are not targeting C++ at the moment. What contexts exist in C where we > require constant expressions? On the top of my head I have array sizes and > initialization of static variables? In such cases, then yes we agree that we
Bit-field widths, static assertions, array designators in initializers, values in enum declarations, case labels, .... It's not always possible to determine the type of an expression without knowing the values of constant expressions within it. An integer constant expression cast to (void *) is a null pointer constant if it has value 0, but not if it has another value. Now look at the rules for the type of conditional expressions between two pointers, which depend on whether one is a null pointer constant. glibc's <tgmath.h> uses that when building with older compilers. GNU __builtin_choose_expr yields simpler cases where a type depends on the value of an integer constant expression. -- Joseph S. Myers jos...@codesourcery.com
