[PATCH v3 2/4] printversion: Fix unused variable

[Ilya Leoshkevich <iii@linux.ibm.com>]

clang complains:

    debuginfod.cxx:354:1: error: unused variable 'apba__' [-Werror,-Wunused-const-variable]
    ARGP_PROGRAM_BUG_ADDRESS_DEF = PACKAGE_BUGREPORT;
    ^
    ../lib/printversion.h:47:21: note: expanded from macro 'ARGP_PROGRAM_BUG_ADDRESS_DEF'
      const char *const apba__ __asm ("argp_program_bug_address")
                        ^

The default linkage for consts in C++ is internal, so declare them
extern. While at it, remove the debuginfod workaround for
argp_program_version_hook.

Co-developed-by: Mark Wielaard <mark@klomp.org>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 debuginfod/debuginfod.cxx | 3 +--
 lib/printversion.h        | 5 ++++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/debuginfod/debuginfod.cxx b/debuginfod/debuginfod.cxx
index 4271acf4..99b1f2b9 100644
--- a/debuginfod/debuginfod.cxx
+++ b/debuginfod/debuginfod.cxx
@@ -348,7 +348,7 @@ static const char DEBUGINFOD_SQLITE_CLEANUP_DDL[] =
 
 
 /* Name and version of program.  */
-/* ARGP_PROGRAM_VERSION_HOOK_DEF = print_version; */ // not this simple for C++
+ARGP_PROGRAM_VERSION_HOOK_DEF = print_version;
 
 /* Bug report address.  */
 ARGP_PROGRAM_BUG_ADDRESS_DEF = PACKAGE_BUGREPORT;
@@ -4171,7 +4171,6 @@ main (int argc, char *argv[])
 
   /* Parse and process arguments.  */
   int remaining;
-  argp_program_version_hook = print_version; // this works
   (void) argp_parse (&argp, argc, argv, ARGP_IN_ORDER, &remaining, NULL);
   if (remaining != argc)
       error (EXIT_FAILURE, 0,
diff --git a/lib/printversion.h b/lib/printversion.h
index a9e059ff..4154b328 100644
--- a/lib/printversion.h
+++ b/lib/printversion.h
@@ -39,10 +39,13 @@ void print_version (FILE *stream, struct argp_state *state);
    argp_program_bug_address, in all programs.  argp.h declares these
    variables as non-const (which is correct in general).  But we can
    do better, it is not going to change.  So we want to move them into
-   the .rodata section.  Define macros to do the trick.  */
+   the .rodata section.  Define macros to do the trick.  The default
+   linkage for consts in C++ is internal, so declare them extern.  */
+extern void (*const apvh) (FILE *, struct argp_state *);
 #define ARGP_PROGRAM_VERSION_HOOK_DEF \
   void (*const apvh) (FILE *, struct argp_state *) \
    __asm ("argp_program_version_hook")
+extern const char *const apba__;
 #define ARGP_PROGRAM_BUG_ADDRESS_DEF \
   const char *const apba__ __asm ("argp_program_bug_address")
 
-- 
2.39.1