[PATCH v4] elf: Fix DFS sorting algorithm for LD_TRACE_LOADED_OBJECTS with missing libraries (BZ #28868)

[Andreas Schwab]

On Mär 04 2022, Adhemerval Zanella via Libc-alpha wrote:

> @@ -2725,3 +2735,50 @@ $(objpfx)tst-p_align3: $(objpfx)tst-p_alignmod3.so
>  $(objpfx)tst-p_align3.out: tst-p_align3.sh $(objpfx)tst-p_align3
>  	$(SHELL) $< $(common-objpfx) '$(test-program-prefix)'; \
>  	$(evaluate-test)
> +
> +
> +# Move the library to a folder so it can be selected by --library-path
> +define libtracemod-mv
> +  test -d $(objpfx)libtracemod$(1) || mkdir $(objpfx)libtracemod$(1)

You can use mkdir -p, which avoids any races.

> +  test -f $(objpfx)libtracemod$(1).so \
> +	  && mv $(objpfx)libtracemod$(1).so $(objpfx)libtracemod$(1)

This will result in a non-zero status if $(objpfx)libtracemod$(1).so
doesn't exist, causing the command to fail.  It's also not race-free.

> +define tst-trace-skeleton
> +$(objpfx)tst-trace$(1).out: $(..)scripts/tst-ld-trace.py \
> +			    $(objpfx)libtracemod1.so \
> +			    libtracemod-mv \
> +			    tst-trace$(1).exp

The dependency on the phony libtracemod-mv will cause the command to
always be rerun.

-- 
Andreas Schwab, schwab@linux-m68k.org
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