Fix ruby-odbc on Ruby-2.4 and MINGW

0001-Fix-Ruby-2.4-MINGW-build.patch

From 53fe2f8c992c28d57b19733723ce43f260376eac Mon Sep 17 00:00:00 2001
From: Lars Kanis <[email protected]>
Date: Wed, 6 Dec 2017 08:53:24 +0100
Subject: [PATCH] Fix Ruby-2.4 MINGW build

Since the following commit to Ruby-2.4, have_library() with an empty function
is no longer treated as "main()". Therefore
"gem install ruby-odbc -v 0.99998" fails on RubyInstaller-2.4 currently.
https://github.com/ruby/ruby/commit/6ff3a8e3bb6c6cf25c134300ebf9877907d739c1

Calling have_library() with one argument fixes this issue.
Calling have_library() with the desired function name as second parameter,
works with RubyInstaller-2.4, but fails on older versions, so that it's
probably best to omit the function name.

The patch has been tested on RubyInstaller-2.0, 2.2, 2.3 and 2.4 and on both
i386 and x86_64.
---
 ext/extconf.rb      | 6 +++---
 ext/utf8/extconf.rb | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/ext/extconf.rb b/ext/extconf.rb
index 5e7023c..eb35b6f 100644
--- a/ext/extconf.rb
+++ b/ext/extconf.rb
@@ -124,9 +124,9 @@ if PLATFORM =~ /mswin32/ then
   have_func("SQLInstallerError", "odbcinst.h")
 # mingw untested !!!
 elsif PLATFORM =~ /(mingw|cygwin)/ then
-  have_library("odbc32", "")
-  have_library("odbccp32", "")
-  have_library("user32", "")
+  have_library("odbc32")
+  have_library("odbccp32")
+  have_library("user32")
 elsif (testdlopen && PLATFORM !~ /(macos|darwin)/ && CONFIG["CC"] =~ /gcc/ && have_func("dlopen", "dlfcn.h") && have_library("dl", "dlopen")) then
   $LDFLAGS+=" -Wl,-init -Wl,ruby_odbc_init -Wl,-fini -Wl,ruby_odbc_fini"
   $CPPFLAGS+=" -DHAVE_SQLCONFIGDATASOURCE"
diff --git a/ext/utf8/extconf.rb b/ext/utf8/extconf.rb
index 344329f..aa99196 100644
--- a/ext/utf8/extconf.rb
+++ b/ext/utf8/extconf.rb
@@ -113,9 +113,9 @@ if PLATFORM =~ /mswin32/ then
   have_func("SQLInstallerError", "odbcinst.h")
   have_func("SQLInstallerErrorW", "odbcinst.h")
 elsif PLATFORM =~ /(mingw|cygwin)/ then
-  have_library("odbc32", "")
-  have_library("odbccp32", "")
-  have_library("user32", "")
+  have_library("odbc32")
+  have_library("odbccp32")
+  have_library("user32")
   header = ["windows.h", "odbcinst.h"]
   have_func("SQLConfigDataSourceW", header)
   have_func("SQLWriteFileDSNW", header)
-- 
2.6.2.windows.1