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ld: new options --ctf-variables and --ctf-share-types

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libctf recently changed to make it possible to not emit the CTF
variables section.  Make this the default for ld: the variables section
is a simple name -> type mapping, and the names can be quite voluminous.
Nothing in the variables section appears in the symbol table, by
definition, so GDB cannot make use of them: special-purpose projects
that implement their own analogues of symbol table lookup can do so, but
they'll need to tell the linker to emit the variables section after all.

The new --ctf-variables option does this.

The --ctf-share-types option (valid values "share-duplicated" and
"share-unconflicted") allow the caller to specify the CTF link mode.
Most users will want share-duplicated, since it allows for more
convenient debugging: but very large projects composed of many decoupled
components may want to use share-unconflicted mode, which places types
that appear in only one TU into per-TU dicts.  (They may also want to
relink the CTF using the ctf_link API and cu-mapping, to make their
"components" larger than a single TU.  Right now the linker does not
expose the CU-mapping machinery.  Perhaps it should in future to make
this use case easier.)

For now, giving the linker the ability to emit share-duplicated CTF lets
us add testcases for that mode to the testsuite.

ld/
	* ldlex.h (option_values) <OPTION_CTF_VARIABLES,
	OPTION_NO_CTF_VARIABLES, OPTION_CTF_SHARE_TYPES>: New.
	* ld.h (ld_config_type) <ctf_variables, ctf_share_duplicated>:
	New fields.
	* ldlang.c (lang_merge_ctf): Use them.
	* lexsup.c (ld_options): Add ctf-variables, no-ctf-variables,
	ctf-share-types.
	(parse_args) <OPTION_CTF_VARIABLES, OPTION_NO_CTF_VARIABLES,
	OPTION_CTF_SHARE_TYPES>: New cases.
	* ld.texi: Document new options.
	* NEWS: Likewise.
This commit is contained in:
Nick Alcock 2020-06-05 23:18:06 +01:00
parent f320bba50f
commit 5dba6f05b7
7 changed files with 107 additions and 1 deletions
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29
ld/lexsup.c
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@ -572,6 +572,18 @@ static const struct ld_option ld_options[] =
{ {"no-print-map-discarded", no_argument, NULL, OPTION_NO_PRINT_MAP_DISCARDED},
'\0', NULL, N_("Do not show discarded sections in map file output"),
TWO_DASHES },
{ {"ctf-variables", no_argument, NULL, OPTION_CTF_VARIABLES},
'\0', NULL, N_("Emit names and types of static variables in CTF"),
TWO_DASHES },
{ {"no-ctf-variables", no_argument, NULL, OPTION_NO_CTF_VARIABLES},
'\0', NULL, N_("Do not emit names and types of static variables in CTF"),
TWO_DASHES },
{ {"ctf-share-types=<method>", required_argument, NULL,
OPTION_CTF_SHARE_TYPES},
'\0', NULL, N_("How to share CTF types between translation units.\n"
" <method> is: share-unconflicted (default),\n"
" share-duplicated"),
TWO_DASHES },
};
#define OPTION_COUNT ARRAY_SIZE (ld_options)
@ -1637,6 +1649,23 @@ parse_args (unsigned argc, char **argv)
case OPTION_DEPENDENCY_FILE:
config.dependency_file = optarg;
break;
case OPTION_CTF_VARIABLES:
config.ctf_variables = TRUE;
break;
case OPTION_NO_CTF_VARIABLES:
config.ctf_variables = FALSE;
break;
case OPTION_CTF_SHARE_TYPES:
if (strcmp (optarg, "share-unconflicted") == 0)
config.ctf_share_duplicated = FALSE;
else if (strcmp (optarg, "share-duplicated") == 0)
config.ctf_share_duplicated = TRUE;
else
einfo (_("%F%P: bad --ctf-share-types option: %s\n"), optarg);
break;
}
}