On Mon, 9 Sep 2019, Matthias Klose wrote:
> On 09.09.19 14:02, Richard Biener wrote:
> > So this is really a very poor mans solution that also might
> > uncover issues with -g0 at compile-time vs. -g at link-time
> > if there are mixed -g0/g TUs in the LTO link.
>
> Could this be documented, at least in the man page? e.g. invoke.texi. As a
> bonus I would very much welcome a section in the user manual about LTO
> building. E.g. what will work, what currently doesn't work, etc. Happy to
> review and extend such documentation, but I don't feel comfortable to write
> that on my own.
Like the following?
Richard.
2019-09-09 Richard Biener <rguent...@suse.de>
* lto-opts.c (lto_write_options): Stream -g when debug is enabled.
* lto-wrapper.c (merge_and_complain): Pick up -g.
(append_compiler_options): Likewise.
(run_gcc): Re-instantiate handling -g0 at link-time.
* doc/invoke.texi (flto): Document debug info generation.
Index: gcc/lto-opts.c
===================================================================
--- gcc/lto-opts.c (revision 275454)
+++ gcc/lto-opts.c (working copy)
@@ -94,6 +94,10 @@ lto_write_options (void)
: "-fno-pie");
}
+ /* If debug info is enabled append -g. */
+ if (debug_info_level > DINFO_LEVEL_NONE)
+ append_to_collect_gcc_options (&temporary_obstack, &first_p, "-g");
+
/* Append options from target hook and store them to offload_lto section. */
if (lto_stream_offload_p)
{
Index: gcc/lto-wrapper.c
===================================================================
--- gcc/lto-wrapper.c (revision 275454)
+++ gcc/lto-wrapper.c (working copy)
@@ -265,6 +265,7 @@ merge_and_complain (struct cl_decoded_op
case OPT_fshow_column:
case OPT_fcommon:
case OPT_fgnu_tm:
+ case OPT_g:
/* Do what the old LTO code did - collect exactly one option
setting per OPT code, we pick the first we encounter.
??? This doesn't make too much sense, but when it doesn't
@@ -617,6 +618,7 @@ append_compiler_options (obstack *argv_o
case OPT_fopenacc:
case OPT_fopenacc_dim_:
case OPT_foffload_abi_:
+ case OPT_g:
case OPT_O:
case OPT_Ofast:
case OPT_Og:
@@ -1399,6 +1401,10 @@ run_gcc (unsigned argc, char *argv[])
linker_output_rel = !strcmp (option->arg, "rel");
break;
+ case OPT_g:
+ /* Recognize -g0. */
+ skip_debug = option->arg && !strcmp (option->arg, "0");
+ break;
default:
break;
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 275454)
+++ gcc/doc/invoke.texi (working copy)
@@ -10335,6 +10335,14 @@ conflicting translation units. Specific
precedence; and for example @option{-ffp-contract=off} takes precedence
over @option{-ffp-contract=fast}. You can override them at link time.
+To enable debug info generation you need to supply @option{-g} at
+compile-time. If any of the input files at link time were built
+with debug info generation enabled the link will enable debug info
+generation as well. Any elaborate debug info settings
+like the dwarf level @option{-gdwarf-5} need to be explicitely repeated
+at the linker command line and mixing different settings in different
+translation units is discouraged.
+
If LTO encounters objects with C linkage declared with incompatible
types in separate translation units to be linked together (undefined
behavior according to ISO C99 6.2.7), a non-fatal diagnostic may be
