• Carlos Santander B. <Carlos_member pathlink.com> Jul 22 2003
• "Nic Tiger" <tiger7 progtech.ru> Jul 22 2003
• Carlos Santander B. <Carlos_member pathlink.com> Jul 22 2003
• Heinz Saathoff <hsaat bre.ipnet.de> Jul 23 2003

Hello. I have something that looks like this:

#include <stdio.h>
void foo(char **s) {
s=new char*[4];
for (int i=0;i<4;i++)
s[i]=new char[20];
}
void main() {
char **bar;
foo(bar);
for (int i=0;i<4;i++)
printf("%s\n",bar[i]);
}

Why do I get an error about memory not being able to be read? (Sorry if that's
not the exact message, it's a translation)
I also tried with bcc5.5, msvc6 and djgpp2.95, and djgpp was the only one not to
cause that error. What's wrong with the code?

You should write ***:

void foo(char ***s) {
*s=new char*[4];
for (int i=0;i<4;i++)
(*s)[i]=new char[20];
}
void main() {
char **bar;
foo(&bar);
}

What you did is initializing stack variable, which is not returned from
function. So, after function foo(...) executed, the parameter bar remained
unchanged.
DJPP should not differ from other compilers, because your code certainly
contains bug.

Nic Tiger.

"Carlos Santander B." <Carlos_member pathlink.com> wrote in message
news:bfk11b$29dm$1 digitaldaemon.com...
 Hello. I have something that looks like this:

 #include <stdio.h>
 void foo(char **s) {
 s=new char*[4];
 for (int i=0;i<4;i++)
 s[i]=new char[20];
 }
 void main() {
 char **bar;
 foo(bar);
 for (int i=0;i<4;i++)
 printf("%s\n",bar[i]);
 }

 Why do I get an error about memory not being able to be read? (Sorry if


 not the exact message, it's a translation)
 I also tried with bcc5.5, msvc6 and djgpp2.95, and djgpp was the only one


 cause that error. What's wrong with the code?

Thank you, very much.

In article <bfk1uq$2abo$1 digitaldaemon.com>, Nic Tiger says...
You should write ***:

void foo(char ***s) {
*s=new char*[4];
for (int i=0;i<4;i++)
(*s)[i]=new char[20];
}
void main() {
char **bar;
foo(&bar);
}

What you did is initializing stack variable, which is not returned from
function. So, after function foo(...) executed, the parameter bar remained
unchanged.
DJPP should not differ from other compilers, because your code certainly
contains bug.

Nic Tiger.

Carlos Santander B. schrieb...
 I have something that looks like this:
 
 #include <stdio.h>
 void foo(char **s) {


                  ^
When compiled as C++ module you can declare s as a reference

 s=new char*[4];
 for (int i=0;i<4;i++)
 s[i]=new char[20];


to something like this:
    for(int i=0; i<4; ++i) {
      s[i] = new char[20];
      s[i][0] = '0';    // empty string
      // or
      sprintf(s[i], "Line %d", i); // Line 0 to Line 3
    }//for
 }
 void main() {
 char **bar;
 foo(bar);
 for (int i=0;i<4;i++)
 printf("%s\n",bar[i]);
 }
 
 Why do I get an error about memory not being able to be read? (Sorry if that's
 not the exact message, it's a translation)


passed by value. bar as a auto-variable is not initialized by default 
and can contain a garbage value. Accessing this pointer (printf does the 
access) in protected mode usually crashes the program. 

 I also tried with bcc5.5, msvc6 and djgpp2.95, and djgpp was the only one not
to
 cause that error. 


still the printf can print garbage.


- Heinz