update_view_title: Fix NULL dereference at startup #1293
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update_view_title can be called with a `struct view`
where `line` is NULL, and `lines` is 0.
Specifically, along this call stack:
0 update_view_title (view=0x3fdb88 <main_view>) at [...]/tig/src/view.c:690
1 0x0000000000338018 in report_clear () at [...]/tig/src/display.c:565
2 0x00000000003cfe5b in load_view (view=0x3fdb88 <main_view>, prev=0x3fdb88 <main_view>, flags=OPEN_
at [...]/tig/src/view.c:857
3 0x00000000003d0bc0 in open_view (prev=0x0, view=0x3fdb88 <main_view>, flags=OPEN_DEFAULT)
at [...]/tig/src/view.c:894
4 0x00000000003b2932 in open_main_view (prev=0x0, flags=OPEN_DEFAULT) at include/tig/main.h:57
5 0x00000000003b0cca in view_driver (view=0x0, request=REQ_VIEW_MAIN) at [...]/tig/src/tig.c:179
6 0x00000000003af96a in main (argc=1, argv=0x7fffffffddb8) at [...]/tig/src/tig.c:864
Specifically, load_view calls report_clear when `view->lines == 0`,
which calls `update_view_title`, which attempts `&view->line[...]`
on a null `line`.
It's not clear why this doesn't explode today.
I caught it when I ran tig compiled with Zig in debug mode
and it failed with an illegal instruction on the line:
struct line *line = &view->line[view->pos.lineno];
Adding a check for `NULL` or `lines == 0` resolves the issue.
abhinav
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The prior fix was pretty blunt: return early if line is null. However, line isn't really used unless specific conditions are met. Instead of returning early, add a check for the value of line where it's first used. This also allows reducing the scope of the corresponding variables from function to a specific block.
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update_view_title can be called with a
struct viewwhere
lineis NULL, andlinesis 0.Along this call stack:
Specifically, load_view calls report_clear when
view->lines == 0,which calls
update_view_title, which attempts&view->line[...]on a null
line.It's not clear why this doesn't explode today.
I caught it when I ran tig compiled with Zig in debug mode
and it failed with an illegal instruction on the line:
Adding a check for
NULLorlines == 0resolves the issue.