Re: [ptxdist] pkg-config-wrapper libdir confusion, ABI dynamic-linker path.

[Christian Melki <christian.melki@t2data.com>]

On 4/23/21 9:39 AM, Michael Olbrich wrote:
> On Thu, Apr 22, 2021 at 09:59:06PM +0200, Christian Melki wrote:
>> I'm using a crosstool-ng toolchain which adheres to the ld.so ABI path
>> for x86_64 (glibc).
>>
>> Afaiu, ptxdist does not like multilib.
>> But it will happily get the dynamic-linker path which contain a multilib
>> description or just a regular lib64 path.
>>
>> https://git.pengutronix.de/cgit/ptxdist/tree/scripts/lib/ptxd_make_00-init.sh#n169
>>
>> This might be a symbolic link to the real dynamic linker, because a
>> demultilibbed toolchain must still adhere to the ABI specifications.
>> For x86_64: 64-bit, hard-float, LE: /lib64/ld-linux-x86-64.so.2
>>
>> So ptxdist will use lib64 as it's base for libdirs placing various
>> libraries in a lib64 path.
> 
> Right, that was contributed a long time ago. But since I don't have a
> test-case for this, the support for this has not been maintained.
> 
> 
>> But when using the pkg-config-wrapper it looks like all libraries are
>> only statically set from a something /lib path.
>>
>> https://git.pengutronix.de/cgit/ptxdist/tree/scripts/pkg-config-wrapper#n19
> 
> Right, and here it get's ugly. I don't want to rely on some external
> environment variable here. Maybe just search for the paths:
> 
> libdir=( $(find ${prefix} -maxdepth 3 -type d -name pkgconfig )
> 
> Would care to provide a patch for this?
> 
> Michael
> 

Sounds resonable. I can try that and provide a patch that (if?) works
for my case atleast. I'll rebuild a ct-ng toolchain without demultilibbing.

Maybe the following is valuable for someone reading this in the future.
I tinkered with ct-ng glibc extra params passed to configuration and
found these two to be useful to play with in situations like these.

# Forcibly try to set a libpath.
CT_GLIBC_EXTRA_CONFIG_ARRAY="libc_cv_slibdir=/lib"

# Make recognize multiple trusted directories upon start.
# Useful when ABI-spec is looking for /lib64 but stuff is elsewhere.
# The rest is managed with the regular ld.so path options.
CT_GLIBC_CONFIGPARMS="user-defined-trusted-dirs=/lib:/lib64"

>> So building a library yields:
>> $ ls -la platform-tracker/sysroot-target/usr/lib64/libmnl.so*
>> lrwxrwxrwx 2 xxx users    15 Apr 22 21:01
>> platform-tracker/sysroot-target/usr/lib64/libmnl.so -> libmnl.so.0.2.0*
>> lrwxrwxrwx 2 xxx users    15 Apr 22 21:01
>> platform-tracker/sysroot-target/usr/lib64/libmnl.so.0 -> libmnl.so.0.2.0*
>> -rwxr-xr-x 2 xxx users 77216 Apr 22 21:01
>> platform-tracker/sysroot-target/usr/lib64/libmnl.so.0.2.0*
>>
>> $ ls -la platform-tracker/sysroot-target/usr/lib64/pkgconfig/libmnl.pc
>> -rw-r--r-- 2 xxx users 318 Apr 22 21:01
>> platform-tracker/sysroot-target/usr/lib64/pkgconfig/libmnl.pc
>>
>> In the search for the library:
>> PKG_CONFIG_DEBUG_SPEW variable enabling debug spew
>> Adding directory
>> '/home/xxx/work/tracker/bin/platform-tracker/sysroot-target/usr/lib/pkgconfig'
>> from PKG_CONFIG_PATH
>> Adding directory
>> '/home/xxx/work/tracker/bin/platform-tracker/sysroot-target/usr/share/pkgconfig'
>> from PKG_CONFIG_PATH
>> Global variable definition 'pc_sysrootdir' = '/'
>> Global variable definition 'pc_top_builddir' = '$(top_builddir)'
>> Error printing enabled by default due to use of output options besides
>> --exists, --atleast/exact/max-version or --list-all. Value of
>> --silence-errors: 0
>> Error printing enabled
>> Adding virtual 'pkg-config' package to list of known packages
>> Looking for package 'libmnl'
>> Looking for package 'libmnl-uninstalled'
>> No package 'libmnl' found
>>
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> 
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