From 93209958cfbf8805debc0a9a233553f75977f6cc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=BCtzel?= <markus.muetzel@gmx.de>
Date: Wed, 12 Jun 2024 18:49:21 +0200
Subject: [PATCH] GraphBLAS: Check for ability to link with libdl.

On some platforms (like NetBSD), `dlopen` and similar functions are not
in a library. They can be used in any dynamically linked program instead:
https://man.netbsd.org/dlopen.3

Use a feature test during configuration to check whether linking to libdl
is necessary (or possible).
---
 GraphBLAS/CMakeLists.txt | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/GraphBLAS/CMakeLists.txt b/GraphBLAS/CMakeLists.txt
index 8677da436..68811a408 100644
--- a/GraphBLAS/CMakeLists.txt
+++ b/GraphBLAS/CMakeLists.txt
@@ -409,7 +409,9 @@ if ( NOT NO_LIBM )
 endif ( )
 
 # libdl
-if ( NOT WIN32 )
+include ( CheckLibraryExists )
+check_library_exists ( "dl" "dlopen" "${CMAKE_LIBRARY_PATH}" HAVE_DL )
+if ( HAVE_DL AND NOT WIN32 )
     if ( BUILD_SHARED_LIBS )
         target_link_libraries ( GraphBLAS PRIVATE dl )
     endif ( )