[v2] gdb/testsuite: Regenerate the testglue if it is not in path

  From: Shahab Vahedi <shahab@synopsys.com>

For running the  DejaGnu  tests,  some  esoteric  configurations
may require a testglue.   This,  for  instance,  is  true  about
testing ARC  targets  which  uses  its  own  DejaGnu  board  and
a simulator which does not support returning the  pass  or  fail
through the exit code.  Therefore,  for  those  tests  that  use
"gdb_compile" a "gdb_tg.o" file is compiled and  linked  to  the
final executable.

There  are  tests  that  invoke  "gdb_compile"  from   different
directories.   Let's  take  a   look   at   an   example   test:
gdb.base/fullname.exp.  The purpose of this  test  is  to  build
the executable from different directories (absolute vs. relative
vs.  other) and then check if gdb can handle setting breakpoints
accordingly.

When  "gdb_compile"  generates  the  "gdb_tg.o",  it  does   not
do it again  for  the  same  test.   Although  this  might  seem
efficient, it can lead to  problems  when  changing  directories
before the next compile:

  gdb compile failed, arc-elf32-gcc: error: gdb_tg.o:
  No such file or directory

This patch checks if the wrapper file ("gdb_tg.o") is  still  in
reach and if it is not, it will stimulate the generation of  the
wrapper again.

It is worth mentioning that GCC's  DejaGnu  tests  handle  these
scenarios as well and they seem to be more efficient in doing so
by saving the library paths and manipulating them  if  necessary
[1].  However, for GDB tests, that  require  less  compilations,
I think the proposed solution should be fine compared to a  more
full fledged solution from GCC.  The glue file in  our  case  is
only 2 KiB.

Last but not least, I ran the x86_64 tests on an x86_64 host and
found no regression.

[1]
Avid  coders  may  look  for  "set_ld_library_path_env_vars"  in
gcc/testsuite/lib/target-libpath.exp.

gdb/testsuite/ChangeLog:

	* lib/gdb.exp (gdb_wrapper_init): Reset
	"gdb_wrapper_initialized" to 0 if "wrapper_file" does
	not exist.
---
 gdb/testsuite/lib/gdb.exp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)
  

On 2020-02-18 6:51 a.m., Shahab Vahedi wrote:
> From: Shahab Vahedi <shahab@synopsys.com>
> 
> For running the  DejaGnu  tests,  some  esoteric  configurations
> may require a testglue.   This,  for  instance,  is  true  about
> testing ARC  targets  which  uses  its  own  DejaGnu  board  and
> a simulator which does not support returning the  pass  or  fail
> through the exit code.  Therefore,  for  those  tests  that  use

When you say "returning the pass or fail through the exit code", do
you mean the exit codes of the test programs (the value returned
by main)?  If so, it does not really mean "pass" or "fail", in a
testsuite sense.  In which case, it would be clearer to just say
"does not support returning the program's exit code".

I don't know what Tom was referring to when he talked about the cache
directory.  I see that the testsuite Makefile cleans a cache directory,
but I have no idea how things can end up there.  Tom, can you clarify?

It's great if you can manage to have it built only once, but just make
sure it's not racy, like:

1. Test 1 notices testglue.o is not there
2. Test 2 notices testglue.o is not there
3. Test 1 generates testglue.o
4. Test 2 starts to write testglue.o, deleting what was done in step 3,
   gets interrupted half-way
5. Test 1 tries to link the half-baked testglue.o in its executable and fails

An option to have it at a predictable absolute place would be to pass
the result of [standard_output_file testglue.o] to build_wrapper.
It would be rebuilt for each test, but it would make sure that tests
don't interfere with each other.

Simon
  

>>>>> "Simon" == Simon Marchi <simark@simark.ca> writes:

Simon> I don't know what Tom was referring to when he talked about the cache
Simon> directory.  I see that the testsuite Makefile cleans a cache directory,
Simon> but I have no idea how things can end up there.  Tom, can you clarify?

If you write a gdb_caching_proc, it caches its result in the cache directory.
This can speed up parallel builds by avoiding excess work.

However in this case, I'm inclined to just let the patch in as-is, since
it's a specialty thing not affecting most test runs.

Tom