[sr #111172] AC_FC/F77_LIBRARY_LDFLAGS incorrectly picks up flags from 'llc'

[anonymous]

URL:
  <https://savannah.gnu.org/support/?111172>

                 Summary: AC_FC/F77_LIBRARY_LDFLAGS incorrectly picks up flags
from 'llc'
                   Group: Autoconf
               Submitter: None
               Submitted: Thu 16 Jan 2025 12:31:49 PM UTC
                Priority: 5 - Unprioritized
                Severity: 3 - Normal
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: j.reuter@fz-juelich.de
             Open/Closed: Open
         Discussion Lock: Any
        Operating System: GNU/Linux


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Follow-up Comments:


-------------------------------------------------------
Date: Thu 16 Jan 2025 12:31:49 PM UTC By: Anonymous
We recently ran into issues building Score-P (and other software like netCDF)
on an aarch64 system using GH200 system when building a compiler toolchain
based on NVHPC 24.9. Generally, software using `autoconf`, and Fortran + C/C++
might be affected.
The issue boils down to a specific `autoconf` check (`checking for Fortran
libraries of [...]`, see
[_AC_FC_LIBRARY_LDFLAGS](https://github.com/autotools-mirror/autoconf/blob/1f38316f6af7bf63e5e7dd187ff6456e07ad743e/lib/autoconf/fortran.m4#L636)).
On `aarch64`, NVHPC may pass the option `-lsr-complexity-limit=131072` to
`llc`. This flag is incorrectly picked up by `autoconf` and treated as a
linker flag for all further checks, causing them to fail with `[...]/ld:
cannot find -lsr-complexity-limit=131072: No such file or directory`.
Configure will then very likely abort soon after, e.g. with `configure: error:
linking to Fortran libraries from C fails`.


In Score-P, we plan to add the following to one of our `.m4` files, right
after the Fortran check picking up this flag:

```
  AC_F77_LIBRARY_LDFLAGS
+ # Remove -lsr-complexity-limit=<some-number> from FLIBS, as it is
+ # not an actual linker flag, but a flag passed to 'llc'. This flag
+ # was observed in the FLIBS variable when using the NVHPC compiler
+ # on aarch64 systems.
+ FLIBS=`echo ${FLIBS} | sed -e 's/-lsr-complexity-limit=[[0-9]]* //g' -e
's/-lsr-complexity-limit=[[0-9]]*$//g'`
```

with a similar substitution for `FCFLAGS`.
This issue might also show up with other compilers, as `llc` is a LLVM tool.
I haven't explicitly checked this.


The issue can be easily reproduced with this snippet, checked with Autoconf
2.72:

```
AC_PREREQ([2.69])
AC_INIT([autotools-playground], [0.0])
AC_CONFIG_AUX_DIR([build-config])
AC_CONFIG_MACRO_DIRS([build-config/m4])

AM_INIT_AUTOMAKE([1.13.4 -Wall foreign tar-pax])
AM_SILENT_RULES([yes])

AC_PROG_CC
AC_PROG_F77

LT_PREREQ([2.4.6])
LT_INIT
AC_SUBST([LIBTOOL_DEPS])

AC_F77_LIBRARY_LDFLAGS
AC_F77_DUMMY_MAIN([], [], [77])])
AC_F77_WRAPPERS

AC_CONFIG_HEADERS([src/config.h])
AC_CONFIG_FILES([Makefile])
AC_OUTPUT
```

The snippet + output is attached.








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File Attachments:


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Name: reproducer.zip  Size: 1MiB
<https://file.savannah.gnu.org/file/reproducer.zip?file_id=56775>

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