[binutils-gdb] Implement and document --gc-keep-exported

[Alan Modra <amodra at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=221855059a11ab76aa909a5df4104354f9384139

commit 221855059a11ab76aa909a5df4104354f9384139
Author: fincs <fincs.alt1@gmail.com>
Date:   Fri Dec 16 13:42:02 2016 +1030

    Implement and document --gc-keep-exported
    
    include/
    	* bfdlink.h (struct bfd_link_info): Add gc_keep_exported.
    bfd/
    	* elflink.c (bfd_elf_gc_mark_dynamic_ref_symbol): Add handling
    	for info->gc_keep_exported.
    	(bfd_elf_gc_sections): Likewise.
    ld/
    	* ld.texinfo: Document --gc-keep-exported.
    	* ldlex.h (enum option_values): Add OPTION_GC_KEEP_EXPORTED.
    	* lexsup.c (parse_args): Add handling for --gc-keep-exported.

Diff:
---
 bfd/ChangeLog     |  6 ++++++
 bfd/elflink.c     |  3 ++-
 include/ChangeLog |  4 ++++
 include/bfdlink.h |  3 +++
 ld/ChangeLog      |  6 ++++++
 ld/ld.texinfo     | 12 ++++++++++++
 ld/ldlex.h        |  1 +
 ld/lexsup.c       |  6 ++++++
 8 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 46cb383..8c09c2c 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,9 @@
+2016-12-16  fincs  <fincs.alt1@gmail.com>
+
+	* elflink.c (bfd_elf_gc_mark_dynamic_ref_symbol): Add handling
+	for info->gc_keep_exported.
+	(bfd_elf_gc_sections): Likewise.
+
 2016-12-15  Alan Modra  <amodra@gmail.com>
 
 	PR ld/20968
diff --git a/bfd/elflink.c b/bfd/elflink.c
index fe6662d..07b7901 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -13051,6 +13051,7 @@ bfd_elf_gc_mark_dynamic_ref_symbol (struct elf_link_hash_entry *h, void *inf)
 	      && ELF_ST_VISIBILITY (h->other) != STV_INTERNAL
 	      && ELF_ST_VISIBILITY (h->other) != STV_HIDDEN
 	      && (!bfd_link_executable (info)
+		  || info->gc_keep_exported
 		  || info->export_dynamic
 		  || (h->dynamic
 		      && d != NULL
@@ -13170,7 +13171,7 @@ bfd_elf_gc_sections (bfd *abfd, struct bfd_link_info *info)
     return FALSE;
 
   /* Mark dynamically referenced symbols.  */
-  if (htab->dynamic_sections_created)
+  if (htab->dynamic_sections_created || info->gc_keep_exported)
     elf_link_hash_traverse (htab, bed->gc_mark_dynamic_ref, info);
 
   /* Grovel through relocs to find out who stays ...  */
diff --git a/include/ChangeLog b/include/ChangeLog
index 57ea85e..7e69c42 100644
--- a/include/ChangeLog
+++ b/include/ChangeLog
@@ -1,3 +1,7 @@
+2016-12-16  fincs  <fincs.alt1@gmail.com>
+
+	* bfdlink.h (struct bfd_link_info): Add gc_keep_exported.
+
 2016-12-14  Maciej W. Rozycki  <macro@imgtec.com>
 
 	* elf/mips.h (Elf_Internal_ABIFlags_v0): Also declare struct
diff --git a/include/bfdlink.h b/include/bfdlink.h
index 9b2194f..aea027b 100644
--- a/include/bfdlink.h
+++ b/include/bfdlink.h
@@ -328,6 +328,9 @@ struct bfd_link_info
   /* TRUE if unreferenced sections should be removed.  */
   unsigned int gc_sections: 1;
 
+  /* TRUE if exported symbols should be kept during section gc.  */
+  unsigned int gc_keep_exported: 1;
+
   /* TRUE if every symbol should be reported back via the notice
      callback.  */
   unsigned int notice_all: 1;
diff --git a/ld/ChangeLog b/ld/ChangeLog
index 086434a..8463c7c 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,9 @@
+2016-12-16  fincs  <fincs.alt1@gmail.com>
+
+	* ld.texinfo: Document --gc-keep-exported.
+	* ldlex.h (enum option_values): Add OPTION_GC_KEEP_EXPORTED.
+	* lexsup.c (parse_args): Add handling for --gc-keep-exported.
+
 2016-12-14  Yury Norov <ynorov@caviumnetworks.com>
 
 	* ld/testsuite/ld-aarch64/aarch64-elf.exp: Add tests for tiny and
diff --git a/ld/ld.texinfo b/ld/ld.texinfo
index ec7ff1b..17503eb 100644
--- a/ld/ld.texinfo
+++ b/ld/ld.texinfo
@@ -1558,6 +1558,18 @@ default behaviour (of not listing the sections that are removed) can
 be restored by specifying @samp{--no-print-gc-sections} on the command
 line.
 
+@kindex --gc-keep-exported
+@cindex garbage collection
+@item --gc-keep-exported
+When @samp{--gc-sections} is enabled, this option prevents garbage
+collection of unused input sections that contain global symbols having
+default or protected visibility.  This option is intended to be used for
+executables where unreferenced sections would otherwise be garbage
+collected regardless of the external visibility of contained symbols.
+Note that this option has no effect when linking shared objects since
+it is already the default behaviour.  This option is only supported for
+ELF format targets.
+
 @kindex --print-output-format
 @cindex output format
 @item --print-output-format
diff --git a/ld/ldlex.h b/ld/ldlex.h
index 52f7198..fd29008 100644
--- a/ld/ldlex.h
+++ b/ld/ldlex.h
@@ -101,6 +101,7 @@ enum option_values
   OPTION_NO_GC_SECTIONS,
   OPTION_PRINT_GC_SECTIONS,
   OPTION_NO_PRINT_GC_SECTIONS,
+  OPTION_GC_KEEP_EXPORTED,
   OPTION_HASH_SIZE,
   OPTION_CHECK_SECTIONS,
   OPTION_NO_CHECK_SECTIONS,
diff --git a/ld/lexsup.c b/ld/lexsup.c
index fb0b47f..8ff5d1f 100644
--- a/ld/lexsup.c
+++ b/ld/lexsup.c
@@ -335,6 +335,9 @@ static const struct ld_option ld_options[] =
   { {"no-print-gc-sections", no_argument, NULL, OPTION_NO_PRINT_GC_SECTIONS},
     '\0', NULL, N_("Do not list removed unused sections"),
     TWO_DASHES },
+  { {"gc-keep-exported", no_argument, NULL, OPTION_GC_KEEP_EXPORTED},
+    '\0', NULL, N_("Keep exported symbols when removing unused sections"),
+    TWO_DASHES },
   { {"hash-size=<NUMBER>", required_argument, NULL, OPTION_HASH_SIZE},
     '\0', NULL, N_("Set default hash table size close to <NUMBER>"),
     TWO_DASHES },
@@ -861,6 +864,9 @@ parse_args (unsigned argc, char **argv)
 	case OPTION_PRINT_GC_SECTIONS:
 	  link_info.print_gc_sections = TRUE;
 	  break;
+	case OPTION_GC_KEEP_EXPORTED:
+	  link_info.gc_keep_exported = TRUE;
+	  break;
 	case OPTION_HELP:
 	  help ();
 	  xexit (0);