Re: Fail in dw2-dos-drive.exp

[Doug Evans <dje at google dot com>]

On Mon, Nov 17, 2014 at 9:10 PM, Yao Qi <yao@codesourcery.com> wrote:
>
> The fail in dw2-dos-drive.exp on arm target leads me to looking into
> this test case deeply,
>
>  break 'z:file.c':func^M
>  Cannot access memory at address 0x4^M
>  (gdb) FAIL: gdb.dwarf2/dw2-dos-drive.exp: break 'z:file.c':func
>
> some questions are raised, and the answers to them affect the scope of work,
>
> The test isn't run on mingw32 target because dwarf2_support returns
> false.  AFAIK, dwarf is supported on mingw32, do we want dwarf2_support
> return true for mingw32 target (and cygwin target)?
>
> If we tweak dwarf2_support to return true for mingw32 target, we'll get
> errors like this, because '.4byte' isn't recognized by mingw32 gas.
>
>   dw2-dos-drive.S:19: Error: unknown pseudo-op: `.4byte'
>
> probably we can use '.long' if '.4byte' isn't supported, like
>
> #ifdef __MINGW32__
>        .long XXXX
> #else
>        .4byte XXX
> #endif
>
> the code in function 'func' is '.4byte 0', which can be interpreted as
> different instructions (even invalid instructions) on different
> architectures.  As the result, it causes the fail I mentioned above.  We
> can use dwarf assembler to emit debug info for a .c file, so that the
> function 'func' always has valid code instructions, including a prologue.
> If we use dwarf assembler, we have to teach dwarf assembler to emit
> .4byte/.long and .2byte/.short according to the capability of target
> gas.  This needs some work too.

Hi.

Another alternative, which I kinda like more, is to add .4byte, etc.
to mingw gas.