[stmt.switch], [stmt.goto]
Change: It is now invalid to jump past a declaration with explicit or implicit initializer (except across entire block not entered)
Rationale:
Constructors used in initializers may allocate
resources which need to be de-allocated upon leaving the
block.
Allowing jump past initializers would require
complicated run-time determination of allocation.
Furthermore, any use of the uninitialized object could be a
disaster.
With this simple compile-time rule, C++ assures that
if an initialized variable is in scope, then it has assuredly been
initialized.
Effect on original feature:
Deletion of semantically well-defined feature.
Difficulty of converting:
Semantic transformation.
How widely used:
Seldom.
[stmt.return]
Change: It is now invalid to return (explicitly or implicitly) from a function which is
declared to return a value without actually returning a value
Rationale:
The caller and callee may assume fairly elaborate
return-value mechanisms for the return of class objects.
If
some flow paths execute a return without specifying any value,
the implementation must embody many more complications.
Besides,
promising to return a value of a given type, and then not returning
such a value, has always been recognized to be a questionable
practice, tolerated only because very-old C had no distinction between
void functions and int functions.
Effect on original feature:
Deletion of semantically well-defined feature.
Difficulty of converting:
Semantic transformation.
Add an appropriate return value to the source code, such as zero.
How widely used:
Seldom.
For several years, many existing C implementations have produced warnings in
this case.