From: Simon Marchi <simon.marchi@polymtl.ca>
To: bug-gnulib@gnu.org
Subject: Missing extern "C" in count-one-bits.h?
Date: Thu, 20 Feb 2020 15:15:03 -0500 [thread overview]
Message-ID: <a546f1a8-d142-77ae-214a-ef72dd596cc0@polymtl.ca> (raw)
Hi,
I recently imported the count-one-bits module in GDB. I just noticed this while trying
to build gdb with clang++-9:
arch/arm-get-next-pcs.o:arm-get-next-pcs.c:function thumb_get_next_pcs_raw(arm_get_next_pcs*): error: undefined reference to 'count_one_bits(unsigned int)'
Everything works fine when building with gcc-9.
This is in the gcc build:
$ readelf --syms gnulib/import/count-one-bits.o | grep count_one_bits
164: 0000000000000000 24 FUNC GLOBAL DEFAULT 50 count_one_bits
$ readelf --syms gdb/arch/arm-get-next-pcs.o | grep count_one_bits
770: 0000000000000000 24 FUNC WEAK DEFAULT 281 _Z14count_one_bitsj
This is in the clang build:
$ readelf --syms gnulib/import/count-one-bits.o | grep count_one_bits
6: 0000000000000000 64 FUNC GLOBAL DEFAULT 2 count_one_bits
$ readelf --syms gdb/arch/arm-get-next-pcs.o | grep count_one_bits
109: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND _Z14count_one_bitsj
The disagreement between the symbol names between count-one-bits.o and arm-get-next-pcs.o
seems to show that there is a missing `extern "C"` in the count-one-bits.h header?
And apparently, gcc decided to compile the definition in the header and include
it in arm-get-next-pcs.o, while clang did not. Is that the compiler's choice,
or is it because the macros and preprocessor conditionals in count-one-bits.h
evaluated to something different for the two compilers?
Simon
next reply other threads:[~2020-02-20 20:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-20 20:15 Simon Marchi [this message]
2020-02-21 20:59 ` Missing extern "C" in count-one-bits.h? Paul Eggert
2020-02-21 22:47 ` Simon Marchi via Gnulib discussion list
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