I tried just using GV_ADD, but it gave me a segfault:

==44885== Invalid write of size 8
==44885==    at 0x6BA4D37: boot_MyModule (mymodule.xs:113)
==44885==    by 0x4CB944F: Perl_pp_entersub (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4CB7785: Perl_runops_standard (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C59496: Perl_call_sv (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C5999C: Perl_call_list (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C45138: S_process_special_blocks (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C533EC: Perl_newATTRSUB (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C53AA2: Perl_utilize (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C82FFF: Perl_yyparse (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4CF0918: S_doeval (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4CF143A: Perl_pp_entereval (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4CB7785: Perl_runops_standard (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==  Address 0x18 is not stack'd, malloc'd or (recently) free'd
==44885==
==44885==
==44885== Process terminating with default action of signal 11 (SIGSEGV): dumping core
==44885==  Access not within mapped region at address 0x18
==44885==    at 0x6BA4D37: boot_MyModule (mymodule.xs:113)
==44885==    by 0x4CB944F: Perl_pp_entersub (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4CB7785: Perl_runops_standard (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C59496: Perl_call_sv (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C5999C: Perl_call_list (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C45138: S_process_special_blocks (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C533EC: Perl_newATTRSUB (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C53AA2: Perl_utilize (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4C82FFF: Perl_yyparse (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4CF0918: S_doeval (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4CF143A: Perl_pp_entereval (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==    by 0x4CB7785: Perl_runops_standard (in /export/my_company/Linux_RHEL6_x86_64/lang/perl/5.12/lib/5.12.5/x86_64-linux-thread-multi/CORE/libperl.so)
==44885==  If you believe this happened as a result of a stack
==44885==  overflow in your program's main thread (unlikely but
==44885==  possible), you can try to increase the size of the
==44885==  main thread stack using the --main-stacksize= flag.
==44885==  The main thread stack size used in this run was 10485760.

mymodule.xs:113 is where I'm calling SvIV_set. The same thing happens if I leave $CONSTANT_NAME in the use vars statement, but don't initialize it in BEGIN.

In reply to Re^2: XS: exposing C++ library constant as package variable by wisnij
in thread XS: exposing C++ library constant as package variable by wisnij

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