[PATCH] Update testsuite mechanism to allow object files as source files.

[Andrew Burgess]

* Caroline Tice via Gdb-patches <gdb-patches@sourceware.org> [2020-07-16 09:50:36 -0700]:

> Since this patch will be resulting in something of a policy change, I
> expect there will be a fair
> amount of discussion around it.
> 
> High level summary:
> In some (hopefully rare) cases, certain tests MUST be built with a
> particular compiler to work.  If that compiler is not GCC, then it
> makes it very burdensome for developers to run the GDB testsuite and
> test those tests.  This change allows those tests to use object files
> (generated by the required compiler) as the test source file, so that
> when the test suite is run with GCC those tests will still
> execute/test properly.
> 
> Details:
> This change is motivated by the fact that clang and GCC sometimes generate
> different output, which affects whether or not a test works properly.  The
> particular motivating example is the gdb.dwarf2/dw5-rnglist-test.exp test,
> which tests whether or not GDB is properly reading/handling DWARF v5
> DW_AT_ranges of the form DW_FORM_rnglistx in lexical block dies.  GCC does
> not generate that code, so compiling the test with GCC does not successfully
> test anything. Clang does generate that code, so the only way to properly
> test this is to compile the test case with clang.  A further twist is that
> the GNU assembler currently chokes on DWARF v5 .debug_line sections, because
> they start their file index at 0 instead of 1, and the GNU assembler has not
> been updated to handle this.  This is not a problem for
> assembly files generated by GCC, because GCC generates DWARF v3
> .debug_line sections, even when passed -gdwarf-5.  Clang on the other hand,
> when passed -gdwarf-5, generates DWARF v5 .debug_line tables. So using a
> clang-generated .s file for the test is not an option, because the GNU
> assembler chokes on it.
> 
> This patch updates lib/gdb.exp to allow it to properly handle test
> cases where the source file is in fact an object file, and it updates
> the dw5-rnglist-test to use an object file rather than the .cc file.  This
> in turn makes the test itself compiler-agnostic.

I haven't looked at this particular test, but I think any
justification for this change, especially when the example you cite is
about different DWARF, should include an explanation about why the
existing DWARF assembler can't be used in this case.

Thanks,
Andrew

> 
> 
> -- Caroline Tice
> cmtice@google.com
> 
> gdb/testsuite/ChangeLog
> 
> 2020-07-16  Caroline Tice  <cmtice@google.com>
> 
>         * lib/gdb.exp (build_executable_from_specs): Create output_dir
>         variable from call to standard_output_file; update code that
>         compiles source files to object files and copies them to output
>         directory, to check first and make sure they are not already
>         object file.  If they are already object files, just copy them to
>         output directory.
>         * gdb.dwarf2/dw5-rnglist-test.o: New file (object file)
>         * gdb.dwarf2/dw5-rnglist-test.exp: Update to use .o file rather than
>         .cc file; this removes the dependency of this test on clang and
>         allows it to work with GCC as well.