[Bug target/119854] New: nvptx offloading: omptests' 'xt-declare-target-ctors': 'unresolved symbol __dso_handle'

[tschwinge at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119854

            Bug ID: 119854
           Summary: nvptx offloading: omptests' 'xt-declare-target-ctors':
                    'unresolved symbol __dso_handle'
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Keywords: openacc, openmp
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tschwinge at gcc dot gnu.org
                CC: burnus at gcc dot gnu.org, jakub at gcc dot gnu.org,
                    vries at gcc dot gnu.org
  Target Milestone: ---
            Target: nvptx

For omptests' 'xt-declare-target-ctors'
(<https://github.com/doru1004/omptests/blob/main/xt-declare-target-ctors/test.cpp>),
nvptx offloading compilation currently fails due to:

    unresolved symbol __dso_handle
    collect2: error: ld returned 1 exit status
    nvptx mkoffload: fatal error:
[...]/x86_64-pc-linux-gnu-accel-nvptx-none-gcc returned 1 exit status

GCN offloading compiles fine.  I first thought GCN, via being
'OBJECT_FORMAT_ELF', would get a '__dso_handle' definition via
'libgcc/crtstuff.c':

    #ifdef OBJECT_FORMAT_ELF

    #if DEFAULT_USE_CXA_ATEXIT
    /* Declare the __dso_handle variable.  It should have a unique value
       in every shared-object; in a main program its value is zero.  The
       object should in any case be protected.  This means the instance
       in one DSO or the main program is not used in another object.  The
       dynamic linker takes care of this.
       If __cxa_atexit is not being used, __dso_handle will not be used and
       doesn't need to be defined.  */

    #ifdef TARGET_LIBGCC_SDATA_SECTION
    extern void *__dso_handle __attribute__ ((__section__
(TARGET_LIBGCC_SDATA_SECTION)));
    #endif
    #ifdef HAVE_GAS_HIDDEN
    extern void *__dso_handle __attribute__ ((__visibility__ ("hidden")));
    #endif
    #ifdef CRTSTUFFS_O
    void *__dso_handle = &__dso_handle;
    #else
    void *__dso_handle = 0;
    #endif
    #endif /* DEFAULT_USE_CXA_ATEXIT */

..., but actually it doesn't, due to being '!DEFAULT_USE_CXA_ATEXIT'.  (See
PR119853 "GCN, nvptx: Review 'DEFAULT_USE_CXA_ATEXIT'".)  Instead, it's via
linker magic; running GCN offloading 'ld' with '--trace-symbol=__dso_handle':

    ./a.xamdgcn-amdhsa.mkoffload.hsaco-a.xamdgcn-amdhsa.mkoffload.2.o:
reference to __dso_handle
    <internal>: definition of __dso_handle

(The '__dso_handle'-using code is per 'DEFAULT_USE_CXA_ATEXIT' powerpc64le and
x86_64 GNU/Linux host.)