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Treat common symbol as undefined for --no-define-common

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When --no-define-common is used to build shared library, treat common
symbol as undefined so that common symbols that are referenced from a
shared library to be assigned addresses only in the main program.  This
eliminates the unused duplicate space in the shared library, and also
prevents any possible confusion over resolving to the wrong duplicate
when there are many dynamic modules with specialized search paths for
runtime symbol resolution.

--no-define-common is only allowed when building a shared library.

bfd/

	PR ld/21903:
	* elflink.c (elf_link_add_object_symbols): Treat common symbol
	as undefined for --no-define-common.

include/

	PR ld/21903:
	* bfdlink.h (bfd_link_info): Add inhibit_common_definition.

ld/

	PR ld/21903:
	* ld.h (command_line): Remove inhibit_common_definition.
	* ldgram.y: Replace command_line.inhibit_common_definition with
	link_info.inhibit_common_definition.
	* ldlang.c (lang_common): Likewise.
	* lexsup.c (parse_args): Likewise.
	* ldmain.c (main): Only allow --no-define-common with -shared.
	* testsuite/ld-elf/pr21903.s: New file.
	* testsuite/ld-elf/pr21903a.d: Likewise.
	* testsuite/ld-elf/pr21903b.d: Likewise.
	* testsuite/ld-elf/pr21903c.d: Likewise.
	* testsuite/ld-elf/pr21903d.d: Likewise.
	* testsuite/ld-elf/pr21903e.d: Likewise.
This commit is contained in:
H.J. Lu
2017-08-06 08:18:53 -07:00
parent e2a084f2c1
commit a4819f54c0
16 changed files with 82 additions and 6 deletions
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3
include/bfdlink.h
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@@ -489,6 +489,9 @@ struct bfd_link_info
/* TRUE if generate a 1-byte NOP as suffix for x86 call instruction. */
unsigned int call_nop_as_suffix : 1;
/* TRUE if common symbols should be treated as undefined. */
unsigned int inhibit_common_definition : 1;
/* The 1-byte NOP for x86 call instruction. */
char call_nop_byte;