How do I find the sizeof text char array?Code:struct data { char text[16]; struct data *next; };
How do I find the sizeof text char array?Code:struct data { char text[16]; struct data *next; };
Do a sizeof(x.text), where x is a struct data.
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
You need to have an instance of the struct data, e.g.
Of course, another option is to use a constant, e.g.Code:struct data d; printf("sizeof text is %d\n", sizeof(d.text));
--Code:#define TEXTLEN 16 struct data { char text[TEXTLEN]; ... }
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
C99:Code:#include <stdio.h> struct st { char text[30]; }; int main() { printf ("sizeof x: %zu\n", sizeof((struct st){0}).text); return 0; }
C90?
Code:#include <stdio.h> struct data { char text[16]; struct data *next; }; int main() { printf ( "size = %lu\n", (long unsigned)sizeof ((struct data*)0)->text ); return 0; } /* my output size = 16 */
7. It is easier to write an incorrect program than understand a correct one.
40. There are two ways to write error-free programs; only the third one works.*
Nice one Dave.
Not mine -- just a memory. Took a while to jog it, though:
http://groups.google.com/group/comp....c6ee2af1cce57b
http://groups.google.com/group/comp....7503f767b1795b
[edit]There is some deal with offsetof that I think I'm confusing it with though.
7. It is easier to write an incorrect program than understand a correct one.
40. There are two ways to write error-free programs; only the third one works.*
Boy!
So many cryptic ways... thanks to all!
I find this one easier for me:
sizeof (<struct instance>.<element name>);
This is what I was trying to do, reading an unlimited length char array from an input stream:
See how simple and small C++ version is!Code:#ifdef C #include <stdio.h> struct data { char text[1024]; data *next; }; data *readData(FILE *in) { data *d, *tmp; d = tmp = new data; tmp->next = NULL; while (true) { int n = fread(tmp->text, 1, sizeof(tmp->text)-1, in); tmp->text[n] = '\0'; if (n < (sizeof(tmp->text)-1)) break; tmp->next = new data; tmp = tmp->next; tmp->next = NULL; } return d; } void writeData(data *d, FILE *out) { while (d) { fputs(d->text, out); d = d->next; } } int main() { printf("Enter a really long story please, press Ctrl-Z to end!\n"); data *d = readData(stdin); printf("Your text:\n"); writeData(d, stdout); return 0; } #else #include <iostream> #include <string> using namespace std; int main() { cout << "Enter a really long story please, press Ctrl-Z to end!" << endl; string text; string line; while (getline(cin, line)) text += line + '\n'; cout << "Your text:" << endl << text; return 0; } #endif
What is that?
You see, two versions, two main()s of my program are in the same file, so to toggle the compile, I used this directive!
Side note: I know, my C version will not compile as C file, but it's almost identical to what I would do in C.
You should never return a local pointer! You can never be sure of the consequences.Code:#ifdef C #include <stdio.h> struct data { char text[1024]; data *next; }; data *readData(FILE *in) { data *d, *tmp; d = tmp = new data; tmp->next = NULL; while (true) { int n = fread(tmp->text, 1, sizeof(tmp->text)-1, in); tmp->text[n] = '\0'; if (n < (sizeof(tmp->text)-1)) break; tmp->next = new data; tmp = tmp->next; tmp->next = NULL; } return d; // That is called SUICIDE! }
I would love to change the world but they dont give me the source code!
Rubbish! The only consequence of that example is that one could forget do deallocate the memory returned and cause a memory leak.
You don't know C++ anywhere near as well as you think you do.
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Advice: Take only as directed - If symptoms persist, please see your debugger
Linus Torvalds: "But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong"
zombiezparadize! wow! LOL!!!Ha Ha Ha!
Edit: Was that a little over the top? Sorry. But thanks for a really good laugh
Last edited by manav; 05-07-2008 at 01:16 AM.
Edit2: Actually, I realize that zombie is somewhat right, i.e., never return a local pointer, which, contains a local address!
zombie, the point is do not return the address of local objects, pointer being local is ok, and also i am returning the address obtained from new, which will be available, even after, the function returns.
[I made this separate post, just to update properly and also my post was last, still, iMalc was listed as last post.]
