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D - scanf, char*, access violation

reply "Carlos Santander B." <carlos8294 msn.com> writes:
This compiles correctly:

import c.stdio;
int main(char[][] args) {
        char[] a;
        char[80] b;
        printf('hey: ');
        ubyte n=scanf('%s',b);
        printf('.');
        a=b[0..n-1];
        printf('%.*s'\n,a);
        return 0;
}

But this is the output I get when I run it:

hey: hey
Error: Access Violation

It doesn't pass the scanf(). Why?

-------------------------
Carlos Santander
http://carlos3.netfirms.com/


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Jan 28 2003
parent reply "Andrew Edwards" <aedwards spamfreeamerica.com> writes:
"Carlos Santander B." <carlos8294 msn.com> wrote in message
news:b16l6l$t8p$1 digitaldaemon.com...
 It doesn't pass the scanf(). Why?

try this: import c.stdio; int main(char[][] args) { char[] a; char[80] b; printf('hey: '); ubyte n=scanf('%s',&b); printf('.'); a = b; printf("%.*s\n",a); return 0; }
Jan 28 2003
next sibling parent "Carlos Santander B." <carlos8294 msn.com> writes:
"Andrew Edwards" <aedwards spamfreeamerica.com> escribiσ en el mensaje
news:b16lrf$to4$1 digitaldaemon.com...
| "Carlos Santander B." <carlos8294 msn.com> wrote in message
| news:b16l6l$t8p$1 digitaldaemon.com...
| > It doesn't pass the scanf(). Why?
|
| try this:
|
| import c.stdio;
| int main(char[][] args) {
|         char[] a;
|         char[80] b;
|         printf('hey: ');
|         ubyte n=scanf('%s',&b);
|         printf('.');
|         a = b;
|         printf("%.*s\n",a);
|         return 0;
| }
|
|

Thanks, that worked. I thought that 'char[80] x' was almost like 'char
*x'...

—————————————————————————
Carlos Santander
http://carlos3.netfirms.com/


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Jan 28 2003
prev sibling next sibling parent reply "Carlos Santander B." <carlos8294 msn.com> writes:
"Andrew Edwards" <aedwards spamfreeamerica.com> escribiσ en el mensaje
news:b16lrf$to4$1 digitaldaemon.com...
| "Carlos Santander B." <carlos8294 msn.com> wrote in message
| news:b16l6l$t8p$1 digitaldaemon.com...
| > It doesn't pass the scanf(). Why?
|
| try this:
|
| import c.stdio;
| int main(char[][] args) {
|         char[] a;
|         char[80] b;
|         printf('hey: ');
|         ubyte n=scanf('%s',&b);
|         printf('.');
|         a = b;
|         printf("%.*s\n",a);
|         return 0;
| }
|
|

Actually, it doesn't work. I hadn't checked, but when I printf 'b', it
doesn't print what I wrote.

—————————————————————————
Carlos Santander
http://carlos3.netfirms.com/


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Jan 28 2003
parent "Andrew Edwards" <aedwards spamfreeamerica.com> writes:
 Actually, it doesn't work. I hadn't checked, but when I printf 'b', it
 doesn't print what I wrote.

simpler though, you can type this printf("%.*s\n", b[0 .. b.length]); your approach printf("%.*s\n", b) passes the address of the first memory location to printf and is therefore analagous to printf("%.*s\n", b[0]); "A request to print the first character of the array."
Jan 28 2003
prev sibling parent reply "Carlos Santander B." <carlos8294 msn.com> writes:
"Andrew Edwards" <aedwards spamfreeamerica.com> escribiσ en el mensaje
news:b16lrf$to4$1 digitaldaemon.com...
| "Carlos Santander B." <carlos8294 msn.com> wrote in message
| news:b16l6l$t8p$1 digitaldaemon.com...
| > It doesn't pass the scanf(). Why?
|
| try this:
|
| import c.stdio;
| int main(char[][] args) {
|         char[] a;
|         char[80] b;
|         printf('hey: ');
|         ubyte n=scanf('%s',&b);
|         printf('.');
|         a = b;
|         printf("%.*s\n",a);
|         return 0;
| }
|
|

After trying a lot without any success, I was forced to write my own
function, and read a 'char[]' char by char.

—————————————————————————
Carlos Santander
http://carlos3.netfirms.com/


---
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Jan 28 2003
parent reply Burton Radons <loth users.sourceforge.net> writes:
Carlos Santander B. wrote:
 "Andrew Edwards" <aedwards spamfreeamerica.com> escribiσ en el mensaje
 news:b16lrf$to4$1 digitaldaemon.com...
 | "Carlos Santander B." <carlos8294 msn.com> wrote in message
 | news:b16l6l$t8p$1 digitaldaemon.com...
 | > It doesn't pass the scanf(). Why?
 |
 | try this:
 |
 | import c.stdio;
 | int main(char[][] args) {
 |         char[] a;
 |         char[80] b;
 |         printf('hey: ');
 |         ubyte n=scanf('%s',&b);
 |         printf('.');
 |         a = b;
 |         printf("%.*s\n",a);
 |         return 0;
 | }
 |
 |
 
 After trying a lot without any success, I was forced to write my own
 function, and read a 'char[]' char by char.

You don't need that. What's happening is that D arrays have both a length and a pointer, even when they have static length, so you just need to cast it to a pointer to get rid of that: scanf ("%s", (char *) b); Another thing. The line: a = b; Won't have the effect you want; "a" will have a length of 80. Use: import string; ... a = string.toString ((char *) b); Instead.
Jan 28 2003
parent reply "Carlos Santander B." <carlos8294 msn.com> writes:
"Burton Radons" <loth users.sourceforge.net> escribiσ en el mensaje
news:b17f4s$7a0$1 digitaldaemon.com...
|
| You don't need that.  What's happening is that D arrays have both a
| length and a pointer, even when they have static length, so you just
| need to cast it to a pointer to get rid of that:
|
|      scanf ("%s", (char *) b);
|

I also tried that.

| Another thing.  The line:
|
|     a = b;

I'm not doing that...

|
| Won't have the effect you want; "a" will have a length of 80.  Use:
|
|      import string;
|
|      ...
|      a = string.toString ((char *) b);
|
| Instead.
|

... I do this: a=b[0..strlen(b)-1];

-------------------------
Carlos Santander
http://carlos3.netfirms.com/


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
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Jan 28 2003
next sibling parent "Carlos Santander B." <carlos8294 msn.com> writes:
This whole problem makes me believe that there should be a direct way to
read char[] from the console. It has been requested before, and I think
Pavel got scanf() to read that (not sure, though), but DMD should include
it.

—————————————————————————
Carlos Santander
http://carlos3.netfirms.com/


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
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Jan 28 2003
prev sibling parent reply Burton Radons <loth users.sourceforge.net> writes:
Carlos Santander B. wrote:
 "Burton Radons" <loth users.sourceforge.net> escribiσ en el mensaje
 news:b17f4s$7a0$1 digitaldaemon.com...
 |
 | You don't need that.  What's happening is that D arrays have both a
 | length and a pointer, even when they have static length, so you just
 | need to cast it to a pointer to get rid of that:
 |
 |      scanf ("%s", (char *) b);
 |
 
 I also tried that.

No you didn't, or you had bad code at another part of the program.
 | Won't have the effect you want; "a" will have a length of 80.  Use:
 |
 |      import string;
 |
 |      ...
 |      a = string.toString ((char *) b);
 |
 | Instead.
 |
 
 ... I do this: a=b[0..strlen(b)-1];

This will lop off the last byte; slice parameters aren't inclusive. Here's your code, corrected: import c.stdio, string; void main() { char[] a; char[80] b; printf('hey: '); scanf('%s',(char*)b); printf('.'); a=toString(b); printf('%.*s'\n,a); }
Jan 28 2003
parent "Carlos Santander B." <carlos8294 msn.com> writes:
"Burton Radons" <loth users.sourceforge.net> escribiσ en el mensaje
| Here's your code, corrected:
|
| import c.stdio, string;
| void main() {
|          char[] a;
|          char[80] b;
|          printf('hey: ');
|          scanf('%s',(char*)b);
|          printf('.');
|          a=toString(b);
|          printf('%.*s'\n,a);
| }
|

Thanks

-------------------------
Carlos Santander
http://carlos3.netfirms.com/


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
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Jan 28 2003