On Wed, 20 Oct 2021 08:11:34 GMT, Stefan Karlsson <stef...@openjdk.org> wrote:
> We encountered the following linking error when trying to build Generational
> ZGC on Windows:
>
> jvm.exp : error LNK2001: unresolved external symbol "const
> ZBasicOopIterateClosure<class <lambda_9767402e468f9fc654281195f9700e48>
> >::`vftable'"
> (??_7?$ZBasicOopIterateClosure@V<lambda_9767402e468f9fc654281195f9700e48>@@@@6B@)
>
>
> I narrowed this down to a simple reproducer, which doesn't link when built
> through the HotSpot build system:
>
> #include <functional>
> std::function<void()> = [](){};
>
>
> I found that we have a line in our make files that filters out symbols that
> contain the string vftable (though it checks the mangled name, so a bit hard
> to find):
>
> else ifeq ($(call isTargetOs, windows), true)
> DUMP_SYMBOLS_CMD := $(DUMPBIN) -symbols *.obj
> FILTER_SYMBOLS_AWK_SCRIPT := \
> '{ \
> if ($$7 ~ /??_7.*@@6B@/ && $$7 !~ /type_info/) print $$7; \
> }'
>
>
> The following line prints the vftable symbol if it doesn't contain the string
> 'type_info':
> if ($$7 ~ /??_7.*@@6B@/ && $$7 !~ /type_info/) print $$7;
>
> The printed values are added to a list of symbols that get filtered out of
> the mapfile, which is then passed to the linker.
>
> I can get the code to link if I add a second exception for vftable symbols
> containing the string 'lambda':
> if ($$7 ~ /??_7.*@@6B@/ && $$7 !~ /type_info/ && $$7 !~ /lambda/) print $$7;
>
> I did an additional experiment where I completely removed this filtering of
> vftable symbols. When I did that the linker complained that we used more than
> 64K symbols.
Looks good to me.
make/hotspot/lib/JvmMapfile.gmk line 109:
> 107: #
> 108: # Some usages of C++ lambdas require the vftable symbol of classes
> that use
> 109: # the lambda type as a template parameter. The usage of those classes
> wont
Suggestion:
# the lambda type as a template parameter. The usage of those classes won't
-------------
Marked as reviewed by ihse (Reviewer).
PR: https://git.openjdk.java.net/jdk/pull/6030
