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Re: Unused variables in testsuite
- From: Daniel Jacobowitz <drow at false dot org>
- To: Christophe LYON <christophe dot lyon at st dot com>
- Cc: gdb at sourceware dot org
- Date: Fri, 28 Apr 2006 10:41:58 -0400
- Subject: Re: Unused variables in testsuite
- References: <email@example.com>
On Fri, Apr 28, 2006 at 04:38:56PM +0200, Christophe LYON wrote:
> Is there anywhere a requirement that the compiler should allocate unused
> variable under -O0 ?
This sort of requirement is never documented anywhere; it's just a
question of common practice. Which in practice means GCC, until
someone is interested in making it more portable.
> For instance, consider the test in gdb.cp/m-static.cc , m-static.h,
> You can see that in main() one defines "test4" which is not used, thus
> need not be allocated. Then, using "print test4.elsewhere" under GDB
> fails. [note that in this case the default (empty) constructor for test4
> has no side effects, thus test4 can be eliminated safely]
> In the same way, in gdb.mi/var-cmd.c , mi-var-display.exp, you can see
> that function do_special_tests() defines several variables (eg 'u') and
> does not use them, while the .exp file tries to "-var-create u * u".
> I modified these tests so that the variables are used, and they now pass
> with our compiler.
> May I submit this small patch, or is there a requirement on GCC to
> allocate even unused variables in -O0? (our compiler is not GCC)
I'd recommend submitting it. We (CodeSourcery) have been slowly
submitting patches to allow the testsuite to run with yet another
compiler (ARM's); we hadn't gotten to this one yet, but I think it's in
there somewhere, because I remember having to modify m-static*.