Improve building with LTO

Use symver attribute for symbol versioning instead of .symver
assembler directive when available. Convert to use double @ syntax
for default version in all cases (required when using the attribute).

Add the attributes externally_visible, no_reorder if available when
using assembler directives to improve the situation for < gcc-10.
This is not 100% reliable, though; -flto-partition=none may still be
needed in some cases.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=24498
Signed-off-by: Alexander Miller <alex.miller@gmx.de>

4 files changed, 13 insertions, 6 deletions

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index d35674c7..f7e24a21 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,10 @@
+2021-02-14  Alexander Miller  <alex.miller@gmx.de>
+
+        * core-file.c (dwfl_core_file_report): Move NEW_VERSION before
+        definition.  Replace INTDEF with NEW_INTDEF.
+        * dwfl_module_build_id.c (dwfl_module_build_id): Likewise.
+        * dwfl_report_elf.c (dwfl_report_elf): Likewise.
+
 2021-09-06  Dmitry V. Levin  <ldv@altlinux.org>
 
         * linux-pid-attach.c (read_cached_memory): Remove cast of malloc
diff --git a/libdwfl/core-file.c b/libdwfl/core-file.c
index a0ccc9b3..4e4c9b3c 100644
--- a/libdwfl/core-file.c
+++ b/libdwfl/core-file.c
@@ -440,6 +440,7 @@ __libdwfl_dynamic_vaddr_get (Elf *elf, GElf_Addr *vaddrp)
   return false;
 }
 
+NEW_VERSION (dwfl_core_file_report, ELFUTILS_0.158)
 int
 dwfl_core_file_report (Dwfl *dwfl, Elf *elf, const char *executable)
 {
@@ -625,8 +626,7 @@ dwfl_core_file_report (Dwfl *dwfl, Elf *elf, const char *executable)
      error rather than just nothing found.  */
   return listed > 0 ? listed : retval;
 }
-INTDEF (dwfl_core_file_report)
-NEW_VERSION (dwfl_core_file_report, ELFUTILS_0.158)
+NEW_INTDEF (dwfl_core_file_report)
 
 #ifdef SYMBOL_VERSIONING
 int _compat_without_executable_dwfl_core_file_report (Dwfl *dwfl, Elf *elf);
diff --git a/libdwfl/dwfl_module_build_id.c b/libdwfl/dwfl_module_build_id.c
index 6ca93761..0c198f23 100644
--- a/libdwfl/dwfl_module_build_id.c
+++ b/libdwfl/dwfl_module_build_id.c
@@ -77,6 +77,7 @@ __libdwfl_find_build_id (Dwfl_Module *mod, bool set, Elf *elf)
   return found_build_id (mod, set, build_id_bits, build_id_len, build_id_vaddr);
 }
 
+NEW_VERSION (dwfl_module_build_id, ELFUTILS_0.138)
 int
 dwfl_module_build_id (Dwfl_Module *mod,
                       const unsigned char **bits, GElf_Addr *vaddr)
@@ -102,8 +103,7 @@ dwfl_module_build_id (Dwfl_Module *mod,
   *vaddr = mod->build_id_vaddr;
   return mod->build_id_len;
 }
-INTDEF (dwfl_module_build_id)
-NEW_VERSION (dwfl_module_build_id, ELFUTILS_0.138)
+NEW_INTDEF (dwfl_module_build_id)
 
 #ifdef SYMBOL_VERSIONING
 COMPAT_VERSION (dwfl_module_build_id, ELFUTILS_0.130, vaddr_at_end)
diff --git a/libdwfl/dwfl_report_elf.c b/libdwfl/dwfl_report_elf.c
index 9da86698..a5f0e5e5 100644
--- a/libdwfl/dwfl_report_elf.c
+++ b/libdwfl/dwfl_report_elf.c
@@ -287,6 +287,7 @@ __libdwfl_report_elf (Dwfl *dwfl, const char *name, const char *file_name,
   return m;
 }
 
+NEW_VERSION (dwfl_report_elf, ELFUTILS_0.156)
 Dwfl_Module *
 dwfl_report_elf (Dwfl *dwfl, const char *name, const char *file_name, int fd,
                  GElf_Addr base, bool add_p_vaddr)
@@ -322,8 +323,7 @@ dwfl_report_elf (Dwfl *dwfl, const char *name, const char *file_name, int fd,
 
   return mod;
 }
-INTDEF (dwfl_report_elf)
-NEW_VERSION (dwfl_report_elf, ELFUTILS_0.156)
+NEW_INTDEF (dwfl_report_elf)
 
 #ifdef SYMBOL_VERSIONING
 Dwfl_Module *