Re: [PATCH] perf annotate: Fix crashes on empty annotate windows

[Namhyung Kim <namhyung@kernel.org>]

On Mon, Apr 20, 2026 at 12:52:17PM +0100, James Clark wrote:
> Annotate can open with an empty window if the disassembly tool fails.
> After the linked change, the TUI started assuming there was a current
> annotation line and could assert or segfault in the seek, refresh, and
> source-toggle paths.
> 
> Handle empty annotate windows explicitly: set the asm entry count before
> resetting the browser, return early when refreshing an empty list, and
> ignore source line toggle when there is no current annotation line.
> 
> Fixes the following when opening an annotation:
> 
>   perf: ui/browser.c:125: ui_browser__list_head_seek: Assertion `pos != NULL' failed.
>   Aborted
> 
> Fixes: e201757f7a0a ("perf annotate: Fix source code annotate with objdump")
> Assisted-by: GitHub Copilot:GPT-5.4
> Signed-off-by: James Clark <james.clark@linaro.org>

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung

> ---
>  tools/perf/ui/browser.c           | 3 +++
>  tools/perf/ui/browsers/annotate.c | 5 ++++-
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/ui/browser.c b/tools/perf/ui/browser.c
> index dc88427b4ae5..321187b204d3 100644
> --- a/tools/perf/ui/browser.c
> +++ b/tools/perf/ui/browser.c
> @@ -513,6 +513,9 @@ unsigned int ui_browser__list_head_refresh(struct ui_browser *browser)
>  	struct list_head *head = browser->entries;
>  	int row = 0;
>  
> +	if (browser->nr_entries == 0)
> +		return 0;
> +
>  	if (browser->top == NULL || browser->top == browser->entries)
>                  browser->top = ui_browser__list_head_filter_entries(browser, head->next);
>  
> diff --git a/tools/perf/ui/browsers/annotate.c b/tools/perf/ui/browsers/annotate.c
> index ea17e6d29a7e..0261cd922183 100644
> --- a/tools/perf/ui/browsers/annotate.c
> +++ b/tools/perf/ui/browsers/annotate.c
> @@ -449,6 +449,9 @@ static bool annotate_browser__toggle_source(struct annotate_browser *browser,
>  	struct annotation_line *al;
>  	off_t offset = browser->b.index - browser->b.top_idx;
>  
> +	if (browser->b.nr_entries == 0)
> +		return false;
> +
>  	browser->b.seek(&browser->b, offset, SEEK_CUR);
>  	al = list_entry(browser->b.top, struct annotation_line, node);
>  
> @@ -542,8 +545,8 @@ static void annotate_browser__show_full_location(struct ui_browser *browser)
>  static void ui_browser__init_asm_mode(struct ui_browser *browser)
>  {
>  	struct annotation *notes = browser__annotation(browser);
> -	ui_browser__reset_index(browser);
>  	browser->nr_entries = notes->src->nr_asm_entries;
> +	ui_browser__reset_index(browser);
>  }
>  
>  static int sym_title(struct symbol *sym, struct map *map, char *title,
> 
> ---
> base-commit: 841dbf4871c57ce2da18c4ea7ffac5487d0eda16
> change-id: 20260417-james-perf-annotate-assert-20f520eeb35b
> 
> Best regards,
> -- 
> James Clark <james.clark@linaro.org>
>