Well, a start, anyway. Enough to prevent clang asserting when
switching on an enumerated type, at least.
No idea if this is a sensible approach or not. Feel free to flame 
I think the code dealing with finding the minimum and maximum enum
constants is really ugly, but I can't see a better way to do it with
the current APSInt API. Anyone have ideas?
-Keith
enum-sizing.diff (4.26 KB)
Seems reasonable: I applied it with changes, here are some comments:
+ enum EnumTypePolicy {
+ AlwaysInt,
+ ShortestType
+ };
This should be documented as a whole and each element should be as well. I wrote:
/// EnumTypePolicy - This enum value contains a list of the various policies
/// that a target can have about how enums are converted to integer types.
enum EnumTypePolicy {
AlwaysInt, // 'int' or 'unsigned'
ShortestType // -fshort-enums
};
+ /// integerTypeCompatibleWithEnumType - returns the integer type compatible
+ /// with the given enum type.
+ QualType integerTypeCompatibleWithEnum(EnumDecl *ED, SourceLocation L);
I renamed this to: getEnumDeclIntegerType and made it const. Also, it doesn't need the source location node, because:
+/// integerTypeCompatibleWithEnumType - returns the integer type compatible
+/// with the given enum type.
+QualType ASTContext::integerTypeCompatibleWithEnum(EnumDecl *ED, SourceLocation L) {
+ Decl *D = ED->getFirstElement();
+ EnumConstantDecl *C = cast<EnumConstantDecl>(D);
...
By the time this is called, all enum constants have to have the same type (which is the integer type we want). I replaced this with:
QualType ASTContext::getEnumDeclIntegerType(EnumDecl *ED) const {
if (EnumConstantDecl *C = ED->getEnumConstantList())
return C->getType();
// If the enum list is empty, it is typed as if it contained a single zero
// element [C++ dcl.enum] and is illegal in C (as an extension, we treat it
// the same as C++ does).
switch (Target.getEnumTypePolicy(ED->getLocation())) {
default: assert(0 && "Unknown enum layout policy");
case TargetInfo::AlwaysInt: return UnsignedIntTy; // 0 -> unsigned
case TargetInfo::ShortestType: return UnsignedCharTy; // 0 -> unsigned char
}
}
I will work on making enum layout follow the GCC conventions next and fix some TODO's in the relevant handling code.
Thanks Keith!
-Chris