gdb/506: Member references in a C structure (Linux)

[eldo dot tony at wipro dot com]

>Number:         506
>Category:       gdb
>Synopsis:       Member references in a C structure (Linux)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Apr 23 04:28:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     eldo.tony@wipro.com
>Release:        GNU gdb 5.1
>Organization:
>Environment:
Linux 2.2.4
GCC 2.95.3
This GDB was configured as "i386-slackware-linux"
>Description:
The GNU Debugger (Version 5.1) is giving a segmentation fault for a particular case of  member referencing in a C structure.
 
See the program below.
 
 
 struct house_det {
   int num;
 };
  
 typedef struct house_det house;
  
 main() {
  
 int get_num( house);
 house h1= {10};
 int temp;
  
 temp=get_num(h1);
  
 return;
 }
  
 int get_num(house temp)
 {
  return(temp.num);
 }
 
  
While debugging the above program (with the GUI window on Linux), the following behavior is observed. 
After setting a watch expression inside the function "get_num" for the  structure member "temp.num", when the control returns to the 'main' function a segmentation fault occurs. I think this is because 'temp' is an integer variable in main(), while it is a structure in the function get_num().
However, if I try to set a watch on 'temp.num' in main(), I get a warning, GDB detects a wrong dereference.

Is this a bug ?



>How-To-Repeat:
While debugging the above program (with the GUI window on Linux), the following behavior is observed. 
After setting a watch expression inside the function "get_num" for the  structure member "temp.num", when the control returns to the 'main' function a segmentation fault occurs. 
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: text/plain; name="t.c"
Content-Disposition: inline; filename="t.c"

/* GDB gives segmentation fault */
struct house_det {
  int num;
};

typedef struct house_det house;

main() {

int get_num( house);
house h1= {10};
int temp;

temp=get_num(h1);

return;
}


int get_num(house temp)
{
 int a=0;
 a++;
 return(temp.num);
}