[Bug gdb/26842] New: Wrong repeat count for char arrays

[Bug gdb/26842] New: Wrong repeat count for char arrays

[bmburstein at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26842

            Bug ID: 26842
           Summary: Wrong repeat count for char arrays
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: bmburstein at gmail dot com
  Target Milestone: ---

When a char array ends with a repeated character, the repeat counter is off by
one. This doesn't happen when it is not at the end of the array, or with other
arrays.

Here is my sample program:

1       #include <stdio.h>
2       #include <string.h>
3       int main() {
4        struct {
5         int i[20];
6         char c[20];
7        } s[20];
8        memset(&s,0,sizeof(s));
9        printf("break here\n");
10       s[0].c[19] = 1;
11       printf("and here\n");
12      }


And here is my relevant (annotated) gdb session:

(gdb) b 9
Breakpoint 1 at 0x118c: file t.c, line 9.
(gdb) b 11
Breakpoint 2 at 0x119f: file t.c, line 11.
(gdb) r
Starting program: /home/baruch/a.out

Breakpoint 1, main () at t.c:9
9        printf("break here\n");
(gdb) p s
$1 = {{i = {0 <repeats 20 times>}, c = '\000' <repeats 19 times>} <repeats 20
times>}
//////////// Notice how both `i` and `s` are said to repeat 20 times, but `c`
only 19 times. ////////////
(gdb) c
Continuing.
break here

Breakpoint 2, main () at t.c:11
11       printf("and here\n");
(gdb) p s
$2 = {{i = {0 <repeats 20 times>}, c = '\000' <repeats 19 times>, "\001"}, {i =
{0 <repeats 20 times>}, c = '\000' <repeats 19 times>} <repeats 19 times>}
//////////// Notice how `c` still says it repeats 19 times, but now has another
element after the repeat ////////////


To help with this: My attempts to fix this got as far as figuring out the
problem is in the function `count_next_character` in `valprint.c`, but that is
as far as I could get.

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[Bug gdb/26842] Wrong repeat count for char arrays

[bmburstein at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26842

--- Comment #1 from Baruch <bmburstein at gmail dot com> ---
I was wrong about the source of the problem. It is in the function
generic_printstr (in file valprint.c), which gets a parameter
c_style_terminator, which causes the last char to be removed if it is a '\0',
so this only happens if the character is '\0'. Still seems wrong, but I am not
sure what would be correct.

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