Mingw is giving me this error:Code:char *mid(char *tString, int x1, int x2){ char *rString; int i, l; rString= (char *) malloc(sizeof(char) * x2); l = x1-1; for (i= 0; i<x2; i++) { rString[i] = tString[l]; l++; } rString[x2]= NULL; return rString; }
C:\Users\Harshvardhan\Desktop\RPL\functions.h|30|w arning: assignment makes integer from pointer without a cast [enabled by default]|
and for this line:
And possible reason/cure for this?Code:rString[x2]= NULL;
rString is a pointer (presumably to an array of chars or a string). Therefore rString[x2] is a single char. But NULL is a pointer type, which is not compatible with char. You are probably looking for the null byte/character (yes, slightly confusing) to terminate your string. Try
Code:rString[x2] = '\0';
NULL is a null pointer constant. While it could just be the integer 0, it could also be (void*)0 or something else that ultimately is a null pointer constant.
What you really want is a character constant, so just write:
By the way, as a single letter name, l is a horrible name as it can be confused with 1 on some fonts.Code:rString[x2] = '\0';
Look up a C++ Reference and learn How To Ask Questions The Smart WayOriginally Posted by Bjarne Stroustrup (2000-10-14)
lol... And I always thought that NULL is exactly same as '\0'
On some implementations, it is. Except for spelling, 0 is identical to '\0'. But you should not rely on that.
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I agree... I used it to signify length... And in code::blocks it is same as 1.
I think I should change it with something better.
And...
Thanks laserlight and anduril for help...
Is this a past end of array?
In other words, is the code below correct?
Really tired, so my thinking might be wrong.Code:rString[x2-1] = '\0';
Tim S.
"...a computer is a stupid machine with the ability to do incredibly smart things, while computer programmers are smart people with the ability to do incredibly stupid things. They are,in short, a perfect match.." Bill Bryson
It looks more likely that the malloc should have allocated another char.
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No... x2-1 just make a character less... x2 is fine.
Do you mean rString?
The problem is that stahta01 is correct to say that it is a problem: you're writing to the array out of bounds. If you want to do this, your malloc should have a +1.
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Sorry...... I'm not getting what you mean to say...
When I use x2-1.... I get a character less...
Yes, you get a character less, but it's better than undefined behavior (what array out of bounds accesses result in). Arrays in C start at index 0 and go to index SIZE-1, or in your case x2-1. That is, your current code allocates an array of x2 characters, meaning you have rString[0]...rString[x2-1]. That's it, no more. rString[x2] is out of bounds. Tim's code corrects that in one possible way (by stopping at x2-1). Laserlight suggested another way, which allocates x2+1 characters, so rString[x2] is valid.
I mean that instead of this:
you should write:Code:rString= (char *) malloc(sizeof(char) * x2);
Notice the +1 to account for the null character.Code:rString = malloc(sizeof(*rString) * x2 + 1);
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oh! Really didn't noticed that
Thank you for help... I would replace x2 with x2+1
