Refactor library lookup

* Try every prefix, not just the first one where the file exists.
  The first existing file might be for the wrong architecture or have
  other issues and cannot be loaded.
* Show which directories were searched in error message.
* Only consider /opt/homebrew/lib on darwin-aarch64.
* Only rescue LoadError and RuntimeError, not Exception.
* Refactor in smaller functions to improve readability.
* Fixes #880.
* Example error message:
  Could not open library 'notexist': notexist: cannot open shared object file: No such file or directory. (LoadError)
  Could not open library 'libnotexist.so': libnotexist.so: cannot open shared object file: No such file or directory.
  Searched in <system library path>, /usr/lib, /usr/local/lib, /opt/local/lib

2 files changed, 97 insertions, 54 deletions

diff --git a/lib/ffi/dynamic_library.rb b/lib/ffi/dynamic_library.rb
new file mode 100644
index 0000000..5b2ec31
--- /dev/null
+++ b/lib/ffi/dynamic_library.rb
@@ -0,0 +1,92 @@
+#
+# Copyright (C) 2008-2010 Wayne Meissner
+#
+# This file is part of ruby-ffi.
+#
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice, this
+#   list of conditions and the following disclaimer.
+# * Redistributions in binary form must reproduce the above copyright notice
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
+# * Neither the name of the Ruby FFI project nor the names of its contributors
+#   may be used to endorse or promote products derived from this software
+#   without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.#
+
+module FFI
+  class DynamicLibrary
+    SEARCH_PATH = %w[/usr/lib /usr/local/lib /opt/local/lib]
+    if FFI::Platform::ARCH == 'aarch64' && FFI::Platform.mac?
+      SEARCH_PATH << '/opt/homebrew/lib'
+    end
+
+    SEARCH_PATH_MESSAGE = "Searched in <system library path>, #{SEARCH_PATH.join(', ')}"
+
+    def self.load_library(name, flags)
+      if name == FFI::CURRENT_PROCESS
+        FFI::DynamicLibrary.open(nil, RTLD_LAZY | RTLD_LOCAL)
+      else
+        flags ||= RTLD_LAZY | RTLD_LOCAL
+
+        libnames = (name.is_a?(::Array) ? name : [name])
+        libnames = libnames.map(&:to_s).map { |n| [n, FFI.map_library_name(n)].uniq }.flatten.compact
+        errors = {}
+
+        libnames.each do |libname|
+          lib = try_load(libname, flags, errors)
+          return lib if lib
+
+          unless libname.start_with?("/") || FFI::Platform.windows?
+            SEARCH_PATH.each do |prefix|
+              path = "#{prefix}/#{libname}"
+              if File.exist?(path)
+                lib = try_load(path, flags, errors)
+                return lib if lib
+              end
+            end
+          end
+        end
+
+        raise LoadError, [*errors.values, SEARCH_PATH_MESSAGE].join(".\n")
+      end
+    end
+    private_class_method :load_library
+
+    def self.try_load(libname, flags, errors)
+      orig = libname
+      begin
+        lib = FFI::DynamicLibrary.open(libname, flags)
+        return lib if lib
+
+      # LoadError for C ext & JRuby, RuntimeError for TruffleRuby
+      rescue LoadError, RuntimeError => ex
+        if ex.message =~ /(([^ \t()])+\.so([^ \t:()])*):([ \t])*(invalid ELF header|file too short|invalid file format)/
+          if File.binread($1) =~ /(?:GROUP|INPUT) *\( *([^ \)]+)/
+            libname = $1
+            retry
+          end
+        end
+
+        libr = (orig == libname ? orig : "#{orig} #{libname}")
+        errors[libr] = ex
+        nil
+      end
+    end
+    private_class_method :try_load
+  end
+end
diff --git a/lib/ffi/library.rb b/lib/ffi/library.rb
index 43b2bfe..92d2143 100644
--- a/lib/ffi/library.rb
+++ b/lib/ffi/library.rb
@@ -28,6 +28,8 @@
 # OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.#
 
+require 'ffi/dynamic_library'
+
 module FFI
   CURRENT_PROCESS = USE_THIS_PROCESS_AS_LIBRARY = Object.new
 
@@ -95,62 +97,11 @@ module FFI
     def ffi_lib(*names)
       raise LoadError.new("library names list must not be empty") if names.empty?
 
-      lib_flags = defined?(@ffi_lib_flags) ? @ffi_lib_flags : FFI::DynamicLibrary::RTLD_LAZY | FFI::DynamicLibrary::RTLD_LOCAL
-      ffi_libs = names.map do |name|
-
-        if name == FFI::CURRENT_PROCESS
-          FFI::DynamicLibrary.open(nil, FFI::DynamicLibrary::RTLD_LAZY | FFI::DynamicLibrary::RTLD_LOCAL)
-
-        else
-          libnames = (name.is_a?(::Array) ? name : [ name ]).map(&:to_s).map { |n| [ n, FFI.map_library_name(n) ].uniq }.flatten.compact
-          lib = nil
-          errors = {}
-
-          libnames.each do |libname|
-            begin
-              orig = libname
-              lib = FFI::DynamicLibrary.open(libname, lib_flags)
-              break if lib
-
-            rescue Exception => ex
-              ldscript = false
-              if ex.message =~ /(([^ \t()])+\.so([^ \t:()])*):([ \t])*(invalid ELF header|file too short|invalid file format)/
-                if File.binread($1) =~ /(?:GROUP|INPUT) *\( *([^ \)]+)/
-                  libname = $1
-                  ldscript = true
-                end
-              end
-
-              if ldscript
-                retry
-              else
-                # TODO better library lookup logic
-                unless libname.start_with?("/") || FFI::Platform.windows?
-                  path = ['/usr/lib/','/usr/local/lib/','/opt/local/lib/', '/opt/homebrew/lib/'].find do |pth|
-                    File.exist?(pth + libname)
-                  end
-                  if path
-                    libname = path + libname
-                    retry
-                  end
-                end
-
-                libr = (orig == libname ? orig : "#{orig} #{libname}")
-                errors[libr] = ex
-              end
-            end
-          end
-
-          if lib.nil?
-            raise LoadError.new(errors.values.join(".\n"))
-          end
+      lib_flags = defined?(@ffi_lib_flags) && @ffi_lib_flags
 
-          # return the found lib
-          lib
-        end
+      @ffi_libs = names.map do |name|
+        FFI::DynamicLibrary.send(:load_library, name, lib_flags)
       end
-
-      @ffi_libs = ffi_libs
     end
 
     # Set the calling convention for {#attach_function} and {#callback}