Re: [PATCH v3 5/6] perf tool: Add fallback stubs for missing dependencies

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Feature fallback stubs are generated in the C source file instead of providing dummy inline stubs in the header file.
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commit f19b5b661c978968c83e8af505c2279ba5f83167
Author: Ian Rogers <irogers@google.com>

perf tool: Add fallback stubs for missing dependencies

This commit adds fallback stubs directly in perf.c for commands that have
optional library dependencies, such as libtraceevent and libelf. This ensures
a unified warning is shown when users try to run these commands, rather than
silently omitting them from the commands array.

> diff --git a/tools/perf/perf.c b/tools/perf/perf.c
> index 65bdfd71f6262..6c5baa285b13f 100644
> --- a/tools/perf/perf.c
> +++ b/tools/perf/perf.c
[ ... ]
> @@ -53,6 +54,38 @@ static void __noreturn usage(const char *err)
>  static int use_pager = -1;
>  static FILE *debug_fp = NULL;
>  
> +
> +#ifndef HAVE_LIBTRACEEVENT
> +#define DECLARE_LIBTRACEEVENT_STUB(_cmd) \
> +	int cmd_##_cmd(int argc __always_unused, const char **argv __always_unused) \
> +	{ \
> +		fprintf(stderr, \
> +			"'" #_cmd "' command not available: missing libtraceevent " \
> +			"devel package at build time.\n"); \
> +		return -1; \
> +	}

[Severity: Medium]
Does defining these fallback stubs directly in the C source file violate the
subsystem guidelines for optional features? 

The perf subsystem guide expects that header files provide compatible dummy
inline stubs when a feature define is absent, rather than generating them via
macros directly in the C source file.

> +
> +DECLARE_LIBTRACEEVENT_STUB(timechart)
> +DECLARE_LIBTRACEEVENT_STUB(sched)
> +DECLARE_LIBTRACEEVENT_STUB(kmem)
> +DECLARE_LIBTRACEEVENT_STUB(lock)
> +DECLARE_LIBTRACEEVENT_STUB(trace)
> +DECLARE_LIBTRACEEVENT_STUB(kwork)
> +#endif
[ ... ]

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Sashiko AI review · https://sashiko.dev/#/patchset/20260902154858.2078885-1-irogers@google.com?part=5