Am Freitag, 28. November 2003 23:40 schrieb Andreas Winkelmann:

Am Freitag, 28. November 2003 17:39 schrieb ged.suse@ntlworld.com:

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I'm currently rewriting many of the standard functions in C++. No i'm not wierd, i'm in the process of learning and figured this would be a good exercise.

Anyway, my strlen() function is bringing up a warning. Although I understand what the warning mean, I don't understand why it is a warning. Can someone please quickly point out the technicalities. The main point I sometimes trip up with is pointers and references (as I suspect most people learning C++ encounter)

int *MyStrlen(const char *source) { int i = 0; while (*source) { *source++; i++; } return &i; }

i is a var which is allocated in the context of this function. If you leave the function i is being deleted. But you return the adress of this space from your function this will crash...

Better should be:

int MyStrlen(....) { ... return i; }

-- Andreas

You don't need the '*' before source, when you want to increment the pointer source. The function should look like: int MyStrlen(const char *source) { int i = 0; while(*source) { source++; i++; } return i; } -- Stefan Lang

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Sun, 30 Nov 2003 07:38:35 -0000 alan@ibgames.com wrote:

On 29 Nov 2003 at 16:17, Stefan Lang wrote:

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Am Freitag, 28. November 2003 23:40 schrieb Andreas Winkelmann:

...

Am Freitag, 28. November 2003 17:39 schrieb ged.suse@ntlworld.com:

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I'm currently rewriting many of the standard functions in C++. No i'm not wierd, i'm in the process of learning and figured this would be a good exercise.

In that case you might like to see if you can find a copy of 'The Standard C Library' by PJ Plauger, which is about implimenting the library :)

It's published by Prentice Hall and the ISBN is 0-13-131509-9. Back in 1988-1989 I had the opportunity to implement the C RTL. That was probably one of the most fun assignments I had ever had. Most of the standard C library functions are pretty straightforward. But, there are a few that become a challenge, such as the printf and scanf functions. In my case, many of the smaller functions were to be implemented in assembler for performance reasons.

- -- Jerry Feldman <gaf@blu.org> Boston Linux and Unix user group http://www.blu.org PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.2-rc1-SuSE (GNU/Linux) iD8DBQE/yfbG+wA+1cUGHqkRAk/IAKCEne9qSx3jR0ZIC1YJPgWCcqjmfgCeOtL9 2xhYizardscmKxlDR+7Bg5k= =oLVM -----END PGP SIGNATURE-----