[Bug ld/20152] New: constructors for c++ objects are sometimes discarded when linked via a .a archive

[dmalcolm at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=20152

            Bug ID: 20152
           Summary: constructors for c++ objects are sometimes discarded
                    when linked via a .a archive
           Product: binutils
           Version: 2.27 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
          Assignee: unassigned at sourceware dot org
          Reporter: dmalcolm at redhat dot com
  Target Milestone: ---

I noticed when developing a patch for GCC that C++ objects with global
constructors are sometimes discarded if linked via a .a archive.

I've created a minimal reproducer for this here:
  https://github.com/davidmalcolm/test-ctor

I can turn that into an archive and attach it if that's preferably.

In the example, test-ctor.C contains objects with constructors that should be
run before main.

If linked as a .o file into the final executable, the constructors are run. If
converted to a .a archive first, the constructors are only run if there's
another symbol in the file that's consumed by something in another file.

Note how in test-1 and test-2a, four ctors are run, but in test-2b, only two
ctors are run; the ctors in test-ctors.C appear to be being discarded:

$ ./test-1
foo:foo(test-ctor.C, static foo in emptyish file)
foo:foo(test-ctor.C, foo in anon ns in emptyish file)
foo:foo(test-ctor-main.C, static foo in main file)
foo:foo(test-ctor-main.C, foo in anon ns in main file)
main()

$ ./test-2a
foo:foo(test-ctor-main.C, static foo in main file)
foo:foo(test-ctor-main.C, foo in anon ns in main file)
foo:foo(test-ctor.C, static foo in emptyish file)
foo:foo(test-ctor.C, foo in anon ns in emptyish file)
main()

$ ./test-2b
foo:foo(test-ctor-main.C, static foo in main file)
foo:foo(test-ctor-main.C, foo in anon ns in main file)
main()

Seen with binutils-2.23.88.0.1-13.fc20.x86_64, reproduced with trunk
(f3ad76370f8c79e4ae74ca6826e23bf417d5283a, 2016-05-25).

-- 
You are receiving this mail because:
You are on the CC list for the bug.