Re: Segmentation fault at malloc.c:4232

[Michael Schwendt <mschwendt@xxxxxxxxx>]

On Sat, 1 Mar 2008 06:10:55 +0800, hanpingtian@xxxxxxxxx wrote:

> I just found out when I comment out the line 27, which calls free() to
> free the line got from
> getline(), the program doesn't segmentation fault.
> 
> But the manual of getline() tells us to free the "*lineptr" when it is
> NULL before call getline(). It's the situation in my program.
> 
> With this src.txt:
> (x = 1)
> 1
> it reports "double free or corruption" when doesn't comment line 27:
> 
> *** glibc detected *** ./compiler: double free or corruption (!prev): 0x08c0d2d8

Your theory is false, your code is broken. You really need to free()
the line buffer when it is allocated by getline(). But you call getline()
in a while-loop without resetting the line pointer to NULL. Here's the
fix:

--- compiler.c~ 2008-02-29 07:06:46.000000000 +0100
+++ compiler.c  2008-02-29 23:55:41.000000000 +0100
@@ -25,6 +25,7 @@
        }
 
        free(line);
+    line = NULL;
        STACKfree();
     }