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arnuld
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 Posted: Wed Nov 08, 2006 10:11 am Post subject: confused between declaration & definition |
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1) int i = 3;
2.) int* pi;
3.) int* pi2 = &i
4.) char* pc;
5.) char c;
6) char c2 = 'a'
7.) char* pc2 = &c2
8.) char* ps = "Stroustroup";
9.) extern double d;
2, 4 & 9 are the only declarations here. right ?
i know that 1, 3, 5, 6, 7, 8 are definitions but can we call them
declarations too?
Is 2 a legal declaration?
i dont understand the difference between 7 & 8. |
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Kai-Uwe Bux
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| Posted: Wed Nov 08, 2006 10:11 am Post subject: Re: confused between declaration & definition |
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arnuld wrote:
| Quote: | 1) int i = 3;
2.) int* pi;
3.) int* pi2 = &i
4.) char* pc;
5.) char c;
6) char c2 = 'a'
7.) char* pc2 = &c2
8.) char* ps = "Stroustroup";
9.) extern double d;
2, 4 & 9 are the only declarations here. right ?
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2 and 4 look like definitions to me.
| Quote: | i know that 1, 3, 5, 6, 7, 8 are definitions but can we call them
declarations too?
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Yes, the standard defines [3.1/2]:
A declaration is a definition unless it declares a function without
specifying the function?s body (8.4), it contains the extern specifier
(7.1.1) or a linkage-specification (7.5) and neither an initializer nor
a function-body, it declares a static data member in a class declaration
(9.4), it is a class name declaration (9.1), or it is a typedef
declaration (7.1.3), a using-declaration (7.3.3), or a using-directive
(7.3.4).
As you can see, every definition is a declaration.
| Quote: | Is 2 a legal declaration?
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Looks legal to me. Did you run it by your compiler?
| Quote: | i dont understand the difference between 7 & 8.
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8 is a special case since the right hand side is really const. Usually, when
you define a T*, you are allowed to modify the pointee; and any attempt to
define a T* so that it points to a (an array of) T char should fail. In
order to support C code, there are special provisions for char*.
Best
Kai-Uwe Bux |
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Alf P. Steinbach
Guest
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| Posted: Wed Nov 08, 2006 10:11 am Post subject: Re: confused between declaration & definition |
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* arnuld:
| Quote: | 1) int i = 3;
2.) int* pi;
3.) int* pi2 = &i
4.) char* pc;
5.) char c;
6) char c2 = 'a'
7.) char* pc2 = &c2
8.) char* ps = "Stroustroup";
9.) extern double d;
2, 4 & 9 are the only declarations here. right ?
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All are declarations, but only 9 is a pure declaration (not a definition).
| Quote: | i know that 1, 3, 5, 6, 7, 8 are definitions but can we call them
declarations too?
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Yes. Any definition is a declaration.
| Quote: | Is 2 a legal declaration?
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Yes.
| Quote: | i dont understand the difference between 7 & 8.
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7 declares a pointer to char and initializes it with the address of a
single char.
8 declares a pointer to char and initializes it with the address of the
first char in a zero-terminated sequence of chars (the string "Stroustrup").
8 is bad form (because it means you can try to modify a string literal
without the compiler detecting that error). It's only allowed in order
to have backwards compatibility with old C. Except for interfacing to
old C code that requires it, you should write
char const* ps = "Stroustrup";
or equivalently
const char* ps = "Stroustrup";
--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail? |
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