[doc] Changing libpth for building extensions

[Flamefire]

Where
Possibly ExtUtils::Liblist::ext()

Description

ExtUtils::Liblist::ext() use libpth to search for libraries and custom implementations of it follow suit.
If I understood this correctly libpth is set during the configure/build of Perl itself.

We are in an environment that sets LD_LIBRARY_PATH & LIBRARY_PATH dynamically before building and using extensions.
But this seems to get ignored.

I've seen e.g. Term:Readline:Gnu providing e.g. --libdir to add paths but haven't found any option to modify libpth to have something generic enough.

Is this missing from the documentation, somewhere I haven't found yet or does it not exist at all?

[jkeenan]

Where Possibly ExtUtils::Liblist::ext()

Description

ExtUtils::Liblist::ext() use libpth to search for libraries and custom implementations of it follow suit. If I understood this correctly libpth is set during the configure/build of Perl itself.

We are in an environment that sets LD_LIBRARY_PATH & LIBRARY_PATH dynamically before building and using extensions. But this seems to get ignored.

I've seen e.g. Term:Readline:Gnu providing e.g. --libdir to add paths but haven't found any option to modify libpth to have something generic enough.

Is this missing from the documentation, somewhere I haven't found yet or does it not exist at all?

My impression is that you haven't supplied sufficient information for us to help you with your problem. For example, I can't identify the operating system on which you are experiencing this problem.

Can you supply us with the output of ./perl -Ilib -V for the perl instance in which you are having this problem?

Can you supply us with the sequence of commands that reproduces the problem?

If you have a git checkout of the Perl core distribution (which you should, in order to investigate a problem like this), you can use the following command to locate instances of the string libpth within that checkout:

$  ack -l '\blibpth\b' .

Please note that ExtUtils::Liblist is maintained upstream on CPAN as part of the ExtUtils-MakeMaker distribution. So any code change will first have to be sent to that library's issue tracker/pull request queue and evaluated there before appearing in the Perl core distribution.

[Flamefire]

I'm using a Linux system, SLES 8 to be exact but this applies to any system supporting LD_LIBRARY_PATH & LIBRARY_PATH

Not sure what you need to "reproduce". The question is basically: How to change libpth to respect the current $LIBRARY_PATH or equivalently what to pass to perl such that it is updated to a specific value or some value gets appended or prepended.
Maybe: perl -e 'use Config; print $Config{libpth}'
This should ideally be equal to $LIBRARY_PATH

This needs to be done either generally, via an environment variable or with a flag to perl such that perl MakeFile.PT can pick it up

In the source I have found this place where the value of this config options seems to be determined during configure and not updated on runtime:

perl5/hints/linux.sh

Line 202 in 29cc805

'') plibpth=`LANG=C LC_ALL=C $gcc $ccflags $ldflags -print-search-dirs | grep libraries |

$ ./perl -Ilib -V

Summary of my perl5 (revision 5 version 38 subversion 2) configuration:

Platform:
osname=linux
osvers=4.18.0-513.24.1.el8_9.x86_64
archname=x86_64-linux-thread-multi
uname='linux n1549 4.18.0-513.24.1.el8_9.x86_64 #1 smp thu mar 14 14:20:09 edt 2024 x86_64 x86_64 x86_64 gnulinux '
config_args='-de -Dcc=gcc -Dccflags=-O2 -ftree-vectorize -march=native -fno-math-errno -fPIC -Dinc_version_list=none -Dprefix=/perl -Dinstallscript=/perl/bin -Dscriptdir=/perl/bin -Dscriptdirexp=/perl/bin -Dinstallstyle=lib/perl5 -Dusethreads'
hint=recommended
useposix=true
d_sigaction=define
useithreads=define
usemultiplicity=define
use64bitint=define
use64bitall=define
uselongdouble=undef
usemymalloc=n
default_inc_excludes_dot=define
Compiler:
cc='gcc'
ccflags ='-D_REENTRANT -D_GNU_SOURCE -O2 -ftree-vectorize -march=native -fno-math-errno -fPIC -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
optimize='-O2'
cppflags='-D_REENTRANT -D_GNU_SOURCE -O2 -ftree-vectorize -march=native -fno-math-errno -fPIC -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
ccversion=''
gccversion='13.3.0'
gccosandvers=''
intsize=4
longsize=8
ptrsize=8
doublesize=8
byteorder=12345678
doublekind=3
d_longlong=define
longlongsize=8
d_longdbl=define
longdblsize=16
longdblkind=3
ivtype='long'
ivsize=8
nvtype='double'
nvsize=8
Off_t='off_t'
lseeksize=8
alignbytes=8
prototype=define
Linker and Libraries:
ld='gcc'
ldflags =' -fstack-protector-strong -L/usr/local/lib'
libpth=/usr/local/lib /software/zlib/1.3.1-GCCcore-13.3.0/lib/../lib64 /software/binutils/2.42-GCCcore-13.3.0/lib/../lib64 /lib/../lib64 /usr/lib/../lib64 /software/zlib/1.3.1-GCCcore-13.3.0/lib /software/binutils/2.42-GCCcore-13.3.0/lib /lib /usr/lib /lib64 /usr/lib64 /usr/local/lib64
libs=-lpthread -ldl -lm -lcrypt -lutil -lc
perllibs=-lpthread -ldl -lm -lcrypt -lutil -lc
libc=libc-2.28.so
so=so
useshrplib=false
libperl=libperl.a
gnulibc_version='2.28'
Dynamic Linking:
dlsrc=dl_dlopen.xs
dlext=so
d_dlsymun=undef
ccdlflags='-Wl,-E'
cccdlflags='-fPIC'
lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'

Characteristics of this binary (from libperl):
Compile-time options:
HAS_LONG_DOUBLE
HAS_STRTOLD
HAS_TIMES
MULTIPLICITY
PERLIO_LAYERS
PERL_COPY_ON_WRITE
PERL_DONT_CREATE_GVSV
PERL_HASH_FUNC_SIPHASH13
PERL_HASH_USE_SBOX32
PERL_MALLOC_WRAP
PERL_OP_PARENT
PERL_PRESERVE_IVUV
PERL_USE_SAFE_PUTENV
USE_64_BIT_ALL
USE_64_BIT_INT
USE_ITHREADS
USE_LARGE_FILES
USE_LOCALE
USE_LOCALE_COLLATE
USE_LOCALE_CTYPE
USE_LOCALE_NUMERIC
USE_LOCALE_TIME
USE_PERLIO
USE_PERL_ATOF
USE_REENTRANT_API
USE_THREAD_SAFE_LOCALE
Built under linux
Compiled at Jul 31 2024 10:10:40
@inc:
lib
/perl/lib/perl5/site_perl/5.38.2/x86_64-linux-thread-multi
/perl/lib/perl5/site_perl/5.38.2
/perl/lib/perl5/5.38.2/x86_64-linux-thread-multi
/perl/lib/perl5/5.38.2