[lex.key]
Change: New Keywords
New keywords are added to C++;
see [lex.key].
Rationale:
These keywords were added in order to implement the new
semantics of C++.
Effect on original feature:
Change to semantics of well-defined feature.
Any ISO C programs that used any of these keywords as identifiers
are not valid C++ programs.
Difficulty of converting:
Syntactic transformation.
Converting one specific program is easy.
Converting a large collection
of related programs takes more work.
How widely used:
Common.
[lex.ccon]
Change: Type of character literal is changed from int to char.
Rationale:
This is needed for improved overloaded function argument type
matching.
For example:
int function( int i ); int function( char c ); function( 'x' );
It is preferable that this call match the second version of
function rather than the first.
Effect on original feature:
Change to semantics of well-defined feature.
ISO C programs which depend on
sizeof('x') == sizeof(int)will not work the same as C++ programs.
Difficulty of converting:
Simple.
How widely used:
Programs which depend upon sizeof('x') are probably rare.
Subclause [lex.string]:
Change: String literals made const.
The type of a string literal is changed
from “array of char”
to “array of const char”.
The type of a char16_t string literal is changed
from “array of some-integer-type”
to “array of const char16_t”.
The type of a char32_t string literal is changed
from “array of some-integer-type”
to “array of const char32_t”.
The type of a wide string literal is changed
from “array of wchar_t”
to “array of const wchar_t”.
Rationale:
This avoids calling an inappropriate overloaded function,
which might expect to be able to modify its argument.
Effect on original feature:
Change to semantics of well-defined feature.
Difficulty of converting:
Syntactic transformation. The fix is to add a cast:
char* p = "abc"; // valid in C, invalid in C++ void f(char*) { char* p = (char*)"abc"; // OK: cast added f(p); f((char*)"def"); // OK: cast added }
How widely used:
Programs that have a legitimate reason to treat string literals
as pointers to potentially modifiable memory are probably rare.