ld: error: undefined hidden symbol: Perl_do_ncmp

Fails to link with perl 5.38 and later:

cc  -shared  -L/usr/local/lib -fstack-protector-strong  XS.o  -o blib/arch/auto/Algorithm/Heapify/XS/XS.so        
ld: error: undefined hidden symbol: Perl_do_ncmp
>>> referenced by XS.c
>>>               XS.o:(sift_up)
>>> referenced by XS.c
>>>               XS.o:(sift_down)
>>> referenced by XS.c
>>>               XS.o:(sift_down)
cc: error: linker command failed with exit code 1 (use -v to see invocation)
*** Error code 1

I came here confirm the issue with a similar error log:

gcc -c  -I. -DSILENT_NO_TAINT_SUPPORT -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2 -O3   -DVERSION=\"0.04\" -DXS_VERSION=\"0.04\" -fPIC "-I/usr/local/booking-perl/5.42/lib/CORE"   XS.c
rm -f blib/arch/auto/Algorithm/Heapify/XS/XS.so
LD_RUN_PATH="/usr/lib/pakket/5.42/libraries/active/lib:/usr/lib/pakket/5.42/libraries/active/lib64" gcc  -shared -g1 -O3 -L/usr/local/lib -fstack-protector-strong  XS.o  -o blib/arch/auto/Algorithm/Heapify/XS/XS.so  \
/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/12/ld: XS.o: in function `sift_up':
XS.c:(.text+0x1f1): undefined reference to `Perl_do_ncmp'
/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/12/ld: XS.o: in function `sift_down':
XS.c:(.text+0x7f9): undefined reference to `Perl_do_ncmp'
/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/12/ld: XS.c:(.text+0x811): undefined reference to `Perl_do_ncmp'
/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/12/ld: blib/arch/auto/Algorithm/Heapify/XS/XS.so: hidden symbol `Perl_do_ncmp' isn't defined
/opt/rh/gcc-toolset-12/root/usr/libexec/gcc/x86_64-redhat-linux/12/ld: final link failed: bad value
collect2: error: ld returned 1 exit status
make: *** [Makefile:481: blib/arch/auto/Algorithm/Heapify/XS/XS.so] Error 1

If we look at line 1072 of proto.h at perl5 commit 0351a629e71de127cbfd1b142e9eaa6069deabf5

As we can see was updated in the diff but GitHub's deep linking doesn't seem to support the diff-view.

Sorry this is fixed now in v 5.0

FWIW, this really should not have been removed from core, I fixed this by copying the one from core, which doesn't make sense. Its actually a bit trick to make an efficient function for this, see Perl_do_ncmp()'s code.

@demerphq

FWIW, this really should not have been removed from core, I fixed this by copying the one from core, which doesn't make sense. Its actually a bit trick to make an efficient function for this, see Perl_do_ncmp()'s code.

@demerphq, thanks for the release! I've just build it on our systems!

For the general discussion about hidden functions, maybe you'll want to chime in the discussion on Perl/perl5#23918, especially these comments by @Leont (Perl/perl5#23918 (comment)) and @tonycoz (Perl/perl5#23918 (comment)).

5.43.8 adds sv_numcmp(), sv_numlt(), sv_numgt() etc that handle overloading correctly (more correctly than the 0.03 or 0.06 implementation here) - ticket to come

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ld: error: undefined hidden symbol: Perl_do_ncmp #2

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ld: error: undefined hidden symbol: Perl_do_ncmp #2

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book commented on Oct 9, 2025

ericherman commented on Nov 12, 2025

demerphq commented on Jun 29, 2026

demerphq commented on Jun 29, 2026

book commented on Jun 29, 2026

tonycoz commented on Jun 29, 2026

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