Hi Branden,
> C doesn't _really_ have strings, except at the library level.
> It has character arrays and one grain of syntactic sugar for encoding
> "string literals", which should not have been called that because
> whether they get the null terminator is context-dependent.
>
> char a[5] = "fooba";
> char *b = "bazqux";
>
> I see some Internet sources claim that C is absolutely reliable about
> null-terminating such literals, but I can't agree. The assignment to
> `b` above adds a null terminator, and the one to `a` does not. This
> is the opposite of absolute reliability. Since I foresee someone
> calling me a liar for saying that, I'll grant that if you carry a long
> enough list of exceptional cases for the syntax in your head, both are
> predictable. But it's simply a land mine for the everyday programmer.
- C defines both string literals and strings at the language level,
e.g. main()'s argv[] is defined to contain strings.
- In C, "foo" is a string literal. That is the correct name as it is
not a C string because a string literal may contain explicit NUL bytes
within it which a string may not: "foo\0bar".
- A string literal has an implicit NUL added at its end thus "foo" fills
four bytes.
- A character array may be initialised by a string literal. Successive
elements of the array are set to the string literal's characters,
including the implicit NUL if there is room.
char two[2] = "foo"; // 'f' 'o'
char three[3] = "foo"; // 'f' 'o' 'o'
char four[4] = "foo"; // 'f' 'o' 'o' '\0'
char five[5] = "foo"; // 'f' 'o' 'o' '\0' '\0'
char implicit[] = "foo"; // 'f' 'o' 'o' '\0'
That's it.
- The string literal is reliably terminating by a NUL.
- It is not context dependent whether a string literal has a terminating
NUL.
- It is absolutely reliable and clearly stated in the C standard and in
any other C reference worth its salt.
- There is no need to ‘carry a long enough list of exceptional cases for
the syntax in your head’.
- An ‘everyday C programmer’ will know this simple behaviour by dint of
being a C programmer who writes it every day; there is no landmine
upon which to step. :-)
Hope that helps clear up this corner of C.
--
Cheers, Ralph.
