https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92386
Bug ID: 92386
Summary: gdb issue with variable-shadowing
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: qinzhao at gcc dot gnu.org
Target Milestone: ---
gdb cannot print the correct value of variables if it's shadowed.
please see the following small testing case for an example:
1 #include <stdio.h>
2 int
3 main ()
4 {
5 volatile int v = 0;
6 int i;
7 for (i=0; i < 3; i++)
8 {
9 v++;
10 v++;
11 printf("i = %d outer v 1 is %d\n",i, v);
12 volatile int v = 4;
13 v++;
14 printf("i = %d inner v is %d\n",i, v);
15 }
16 printf("outer v 2 is %d\n", v);
17 }
built it with the latest gcc10 and execute it, no problem:
[qinzhao@localhost ~]$ gcc t.c
[qinzhao@localhost ~]$ ./a.out
i = 0 outer v 1 is 2
i = 0 inner v is 5
i = 1 outer v 1 is 4
i = 1 inner v is 5
i = 2 outer v 1 is 6
i = 2 inner v is 5
outer v 2 is 6
However, when use gdb to check the value of variable v, we will see that at
line 9, 10, the value of "v" is incorrect:
(gdb) run
Starting program: /home/qinzhao/a.out
Breakpoint 1, main () at t.c:9
9 v++;
Missing separate debuginfos, use: debuginfo-install
glibc-2.17-222.ora28641867.1.el7.x86_64
(gdb) print v
$1 = 32767
(gdb) n
10 v++;
(gdb) print v
$2 = 32767
(gdb) n
11 printf("i = %d outer v 1 is %d\n",i, v);
(gdb) n
i = 0 outer v 1 is 2
12 volatile int v = 4;
(gdb) n
13 v++;
(gdb) print v
$3 = 4
(gdb) n
14 printf("i = %d inner v is %d\n",i, v);
(gdb) print v
$4 = 5
(gdb) n
i = 0 inner v is 5
7 for (i=0; i < 3; i++)
(gdb) n
Breakpoint 1, main () at t.c:9
9 v++;
(gdb) print v
$5 = 5
(gdb) n
10 v++;
(gdb) print v
$6 = 5
