buffer overflow with gcc but now with visual C++? why?

[Adam Rinkleff]

fflush(stdin);

	for (i=0; i<=length-1; i++)
	{if (i<=length-1){c=getchar();	input[i]=c;}}
	input[length]=0;

This code works in VisualC++, and if I enter too many letters it just truncates the string; but in gcc I get a buffer overflow and the program crashes. ?? Is there a better way to take user input and crop it as a string of a specified yet variable size?

[CommonTater]

Most likely because of your screwball loop structures...

for (i = 0; i < length; i++)
  { input[i] = getchar();}

input[length-1] = 0;

[quzah]

You don't need that if there, since you've already guaranteed that to be true:

	for (i=0; i<=length-1; i++)
	{if (i<=length-1){c=getchar();	input[i]=c;}}

Here is your problem:

input[length]=0;

Does this:

#define length 3000
int input[ length ];
...
input[ length ] = 0; /* You just ran off the end of your array. */

Quzah.

[Salem]

> buffer overflow with gcc but now with visual C++? why?
Actually, it's buffer overflow with gcc, why isn't it detected by VC++.
The answer is basically luck - you were lucky that it crashed with gcc.


The fflush(stdin) isn't doing you any favours either (see the FAQ).

> Is there a better way to take user input and crop it as a string of a specified yet variable size?
Read ALL input with fgets(), then decide what to do with it once it is in a buffer.