Menu
Doing this in C++
char* cool = "cool";
compiles fine, but gives me a warning:
deprecated conversion from string constant to char*.
I would never willfully use a C-style string over std::string, but just in case I'm asked this question:
is it bad practice to declare a C-style string without the const modifier? If so, why?
530
C string constants can be declared using either pointer syntax or array syntax: // Option 1: using pointer syntax. const char *ptr = "Lorem ipsum"; // Option 2: using array syntax.
const is compile time. When you use const string you end up not using space for this variable during run time. The compiler uses this value in a way not dissimilar to a macro. When you don't use const string it acts like any other variable and occupies additional space during run time.
A valid C string requires the presence of a terminating "null character" (a character with ASCII value 0, usually represented by the character literal '\0' ). Since char is a built-in data type, no header file is required to create a C string.
Strings using character pointers Using character pointer strings can be stored in two ways: 1) Read only string in a shared segment. When a string value is directly assigned to a pointer, in most of the compilers, it's stored in a read-only block (generally in data segment) that is shared among functions.
Yes, this declaration is bad practice, because it allows many ways of accidentally provoking Undefined Behavior by writing to a string literal, including:
cool[0] = 'k'; strcpy(cool, "oops"); On the other hand, this is perfectly fine, since it allocates a non-const array of chars:
char cool[] = "cool"; Yes, in C++ you should always refer to string literals with variables of type const char * or const char [N]. This is also best practice when writing new C code.
String literals are stored in read-only memory, when this is possible; their type is properly const-qualified. C, but not C++, includes a backward compatibility wart where the compiler gives them the type char [N] even though they are stored in read-only memory. This is because string literals are older than the const qualifier. const was invented in the run-up to what's now called "C89" -- the earlier "K&R" form of the language did not have it.
Some C compilers include an optional mode in which the backward compatibility wart is disabled, and char *foo = "..."; will get you the same or a similar diagnostic that it does in C++. GCC spells this mode -Wwrite-strings. I highly recommend it for new code; however, turning it on for old code is liable to require an enormous amount of scutwork for very little benefit.
44
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
