[PATCH v4 mtd-utils 3/4] configure.ac: Add a check for execinfo and backtrace

[Ross Burton]

On 19 Feb 2025, at 13:02, Fabio Estevam <festevam at gmail.com> wrote:
>
> musl relies on an external execinfo library to provide backtrace
> functionality. If musl cannot link to libexecinfo, the following link
> error happens:
>
> Fix the problem by checking for backtrace support in libc first and if not
> found, then check for backtrace support in the external libexecinfo.

If this is the right solution, it’s not complete.

mtd-utils already checks for the presence of execinfo.h and uses that when creating lib/libmissing.a, which if execinfo.h isn’t present will contain a stub backtrace() implementation that simply returns 0.  The test suite already uses this so it can build on systems without musl, but presumably nobody tested mtd-utils on musl after "ubifs-utils: Add implementations for linux kernel printing functions” landed, which added more users of backtrace().

I think either mtd-utils should hard-depend on _something_ providing backtrace(), be it the libc or a drop-in library, or it should use backtrace() if present and gracefully fallback otherwise (as it’s a convenience feature).  Not both, which is what this patch achieves.

I’ll send an alternative patch in a moment which uses libmissing.a instead of relying on an external libexecinfo.

Note that the rest of the series is good, this is the only change I have comments on.

Ross
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