On 01/19/2018 05:35 PM, Jakub Jelinek wrote:
> On Fri, Jan 19, 2018 at 05:33:10PM -0600, Daniel Santos wrote:
>> When stepping through tail-call restore stubs the debugger has to assume
>> that rsp - 8 is the CFA, although it is not. This is because I did not
>> explicitly add any .cfi directives. This patch adds them to the
>> tail-call restore stubs, but this is new territory for me, so I would
>> appreciate feedback.
>>
>> I've reg-tested on x86_64, but I still need to test on Solaris and
>> Darwin. OK to commit after those tests?
> I think you can't assume that the assembler supports .cfi_* directives.
> While e.g. libgcc/config/i386/morestack.S uses them unconditionally,
> it is guarded with:
> if test "$libgcc_cv_cfi" = "yes"; then
> tmake_file="${tmake_file} t-stack i386/t-stack-i386"
> fi
Ah hah! That explains a lot. Yeah, I wasn't thinking all assemblers
would support it but I saw them in the Solaris assembler manual and
figured that they were maybe more widely supported than I had thought.
> in config.host. E.g. cygwin.S has:
> #ifdef HAVE_GAS_CFI_SECTIONS_DIRECTIVE
> .cfi_sections .debug_frame
> # define cfi_startproc() .cfi_startproc
> # define cfi_endproc() .cfi_endproc
> # define cfi_adjust_cfa_offset(X) .cfi_adjust_cfa_offset X
> # define cfi_def_cfa_register(X) .cfi_def_cfa_register X
> # define cfi_register(D,S) .cfi_register D, S
> # ifdef __x86_64__
> # define cfi_push(X) .cfi_adjust_cfa_offset 8; .cfi_rel_offset X, 0
> # define cfi_pop(X) .cfi_adjust_cfa_offset -8; .cfi_restore X
> # else
> # define cfi_push(X) .cfi_adjust_cfa_offset 4; .cfi_rel_offset X, 0
> # define cfi_pop(X) .cfi_adjust_cfa_offset -4; .cfi_restore X
> # endif
> #else
> # define cfi_startproc()
> # define cfi_endproc()
> # define cfi_adjust_cfa_offset(X)
> # define cfi_def_cfa_register(X)
> # define cfi_register(D,S)
> # define cfi_push(X)
> # define cfi_pop(X)
> #endif /* HAVE_GAS_CFI_SECTIONS_DIRECTIVE */
> perhaps you need something similar or commonize that (though, without
> .cfi_sections, you want the default).
>
> Jakub
Thanks. I like the idea of commonizing the macros for consistency.
As far as adding tests, I guess I would need to dig into
lib/gcc-gdb-test.exp to figure out how to do that.
Daniel
