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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.
Dazu noch ganz geile Sachen wie
Change: C++ does not have “tentative definitions” as in C E.g., at file scope,
int i;
int i;
is valid in C, invalid in C++. This makes it impossible to define mutually referential file-local static objects, if initializers are restricted to the syntactic forms of C.
For example,
struct X { int i; struct X *next; };
static struct X a;
static struct X b = { 0, &a };
static struct X a = { 1, &b };
Rationale: This avoids having different initialization rules for fundamental types and user-defined types.
Effect on original feature: Deletion of semantically well-defined feature.
Difficulty of converting: Semantic transformation.
Rationale: In C++, the initializer for one of a set of mutually-referential file-local static objects must invoke
a function call to achieve the initialization.
How widely used: Seldom.
Change: Main cannot be called recursively and cannot have its address taken
Rationale: The main function may require special actions.
Effect on original feature: Deletion of semantically well-defined feature
Difficulty of converting: Trivial: create an intermediary function such as mymain(argc, argv).
How widely used: Seldom
Edit: Mir fällt gerade auf, ich könnte so C lernen... einfach dieses Kompabilitätskapitel durchackern...
