Annex C (informative) Compatibility [diff]

Change: Remove auto as a storage class specifier.

Rationale: New feature.

Effect on original feature: Valid C++ 2003 code that uses the keyword auto as a storage class specifier may be invalid in this revision of C++.

In this revision of C++, auto indicates that the type of a variable is to be deduced from its initializer expression.

Change: Narrowing restrictions in aggregate initializers.

Rationale: Catches bugs.

Effect on original feature: Valid C++ 2003 code may fail to compile in this revision of C++.

For example: int x[] = { 2.0 };

This code is valid in C++ 2003 but invalid in this revision of C++ because double to int is a narrowing conversion.

Change: Names declared in an anonymous namespace changed from external linkage to internal linkage; language linkage applies to names with external linkage only.

Rationale: Alignment with user expectations.

Effect on original feature: Valid C++ 2003 code may violate the one-definition rule ([basic.def.odr]) in this revision of C++.

For example: namespace { extern "C" { extern int x; } } // #1, previously external linkage and C language linkage, // now internal linkage and C++ language linkage namespace A { extern "C" int x = 42; } // #2, external linkage and C language linkage int main(void) { return x; }

This code is valid in C++ 2003, but #2 is not a definition for #1 in this revision of C++, violating the one-definition rule.