An integer constant expression (ICE) is a restricted C expression whose integer value is determined at compile time. It cannot call a function or evaluate an object as an operand. Integer literals and enumeration constants can participate; _Alignof, offsetof, and some sizeof expressions may also qualify. section 5.6.2
Literal versus object
signed const o42 = 42; enum { b42 = 42, // OK: literal c52 = o42 + 10, // Error: evaluates an object b52 = b42 + 10, // OK: enumeration constant }; TAKEAWAY: const qualification does not make an object usable in an integer constant expression. section 5.6.2
The restriction matters directly in switch statements: every case value must be an integer constant expression. A variable such as count may control switch, but cannot serve as an individual case value. section 3.3
enum corvid { magpie, raven, jay, corvid_num, };
char const*const bird[corvid_num] = {
[raven] = "raven",
[magpie] = "magpie",
[jay] = "jay",
};
...
for (unsigned i = 0; i < corvid_num; ++i)
printf("Corvid %u is the %s\n", i, bird[i]);
!@%STYLE%@!
{"css":"{\"css\": \"font-weight: bold;\"}","target":"[[{\"line\":0,\"ch\":0},{\"line\":0,\"ch\":4}],[{\"line\":1,\"ch\":0},{\"line\":1,\"ch\":10}],[{\"line\":1,\"ch\":5},{\"line\":1,\"ch\":10}],[{\"line\":7,\"ch\":0},{\"line\":7,\"ch\":3}],[{\"line\":7,\"ch\":5},{\"line\":7,\"ch\":13}],[{\"line\":8,\"ch\":4},{\"line\":8,\"ch\":10}]]"}
!@%STYLE%@!
Browse an enumeration and indexed string array using compile-time enumeration constants such as raven, magpie, jay, and corvid_num. section 5.6.2
