Date: Sun, 17 Apr 2022 19:21:11 -0700 From: Mark Millard <marklmi@yahoo.com> To: freebsd-ports@freebsd.org, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Use of lang/gcc*'s g++* via the likes of USE_GCC=11:build+ in ports when a -Wl,-rpath=/usr/local/lib/gcc* is required: How? Message-ID: <90BF482E-BE98-4783-8440-9FA0E03E3D88@yahoo.com> References: <90BF482E-BE98-4783-8440-9FA0E03E3D88.ref@yahoo.com>
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I'll use g++11 as an example here. By no means is the issue
limited to g++11 . Also, the general issue is not limited
to the specifics of the other aspects of the example I report
below.
EXAMPLE PROBLEM:
FreeBSD's /lib/libgcc_s.so.1 is insufficient for what aarch64
g++11 code generation expects to be provided. Programs can be
built but end up with notices that start with:
ld-elf.so.1: /lib/libgcc_s.so.1: version GCC_4.5.0 required by
. . . not found
Sometimes the ". . ." is /usr/local/lib/gcc11/libstdc++.so.6 .
Other times it does not get that far because the program
itself has the issue before shared libraries are bound. A
simple 6 line program on aarch64 can show the issue:
# more fp-binding-failure-aarch64.cpp
#include <cmath>
volatile long double v=3DNAN;
int main()
{
return std::isnan(v) ? 1 : 0;
}
# g++11 fp-binding-failure-aarch64.cpp
# ./a.out
ld-elf.so.1: /lib/libgcc_s.so.1: version GCC_4.5.0 required by =
/usr/home/root/c_tests/a.out not found
The a.out has its own reference to=20
__unordtf2@GCC_4.5.0 :
# nm -a a.out | grep '@GCC_[4-9]\.' | more
U=20
__unordtf2@GCC_4.5.0
For reference . . .
# ldd a.out
a.out:
libstdc++.so.6 =3D> /usr/local/lib/gcc11/libstdc++.so.6 =
(0x83000000)
libm.so.5 =3D> /lib/libm.so.5 (0x81834000)
libgcc_s.so.1 =3D> /lib/libgcc_s.so.1 (0x8275a000)
libc.so.7 =3D> /lib/libc.so.7 (0x845f3000)
Use of -Wl,-rpath=3D/usr/local/lib/gcc11 avoids the example's
failure by using gcc11's libgcc_s.so.1 instead of FreeBSD's.
gcc11's libgcc_s.so.1 is more likely to accurately cover
the g++11 compiler's potential range of code generation.
I've no clue what all g++11 targeting aarch64 generates that
also would not be found in /lib/libgcc_s.so.1 on aarch64.
Similarly, I do not know what examples might exist for other
FreeBSD platforms. But aarch64 is tier 1 these days, if that
matters for this subject area.
THE QUESTION:
How does one use the likes of USE_GCC=3D11:build+ and also
supply the appropriate -Wl,-rpath=3D/usr/local/lib/gcc??
to match which g++ is actually used?
There is an analogous question for when using a linker
command line directly instead (no -Wl, prefix).
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
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