error: in-class initializer is not a constant expression

[llvmbot]

Bugzilla Link	9997
Resolution	INVALID
Resolved on	May 23, 2011 19:34
Version	2.9
OS	MacOS X
Attachments	error: in-class initializer is not a constant expression
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor

Extended Description

Z% clang++ --version
Apple clang version 2.0 (tags/Apple/clang-139) (based on LLVM 2.9svn)
Target: x86_64-apple-darwin10
Thread model: posix
Z% cat clang-error-in-class-initializer-is-not-a-constant-expression.cpp

template
class foo {
public:
static const int width;
};

template const int foo::width = 1;

struct bar {
static const int baz = foo<255>::width;
};
Z% clang++ -c clang-error-in-class-initializer-is-not-a-constant-expression.cpp
clang-error-in-class-initializer-is-not-a-constant-expression.cpp:11:26: error: in-class initializer is not a constant
expression
static const int baz = foo<255>::width;
^~~~~~~~~~~~~~~
1 error generated.
Z%

[DougGregor]

Clang is correct to reject this code, because the initializer is not constant unless it was written within the class definition.