From 3a7034f2fd1060b2a1fc9d015f6df7fe73f18cf6 Mon Sep 17 00:00:00 2001
From: Samuel Dionne-Riel <samuel@dionne-riel.com>
Date: Mon, 24 Feb 2020 20:01:47 -0500
Subject: [PATCH] Nixpkgs: dump linker flags for re-use

Dumping the flags the build-system used is useful to allow re-using them
to compile custom binaries, via mrbc + custom gcc invocations.

Actually using the flags as defined by gems and mruby is much better
than hoping we're not forgetting to define some in the project-specific
builder.
---
 Rakefile | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/Rakefile b/Rakefile
index 28e2d75c..5a13046a 100644
--- a/Rakefile
+++ b/Rakefile
@@ -157,3 +157,45 @@ task :deep_clean => ["clean", "clean_doc"] do
   end
   puts "Cleaned up mrbgems build folder"
 end
+
+desc "Output linker flags"
+task :dump_linker_flags do
+  # This assumes the first defined target is the desired one.
+  # [{ host: ...   }]
+  #  ^first  ^last
+  target = MRuby.targets.first.last
+  require "shellwords"
+
+  File.open("mruby_linker_flags.sh", "w") do |file|
+    file.puts "mrb_cflags=("
+    file.puts target.cc.all_flags
+    file.puts ")"
+    file.puts ""
+    [:flags, :flags_before_libraries, :flags_after_libraries, :libraries, :library_paths].each do |sym|
+      contents = [
+        target.linker.send(sym),
+        *target.gems.map { |g| g.linker.send(sym) },
+      ].flatten
+      file.puts "mrb_linker_#{sym}=("
+      file.puts contents.shelljoin
+      file.puts ")"
+      file.puts ""
+    end
+    contents = [
+      target.linker.libraries,
+      *target.gems.map { |g| g.linker.libraries },
+    ].flatten
+    file.puts "mrb_linker_libraries_flags=("
+    file.puts contents.map{|lib| "-l#{lib}"}.shelljoin
+    file.puts ")"
+    file.puts ""
+    contents = [
+      target.linker.library_paths,
+      *target.gems.map { |g| g.linker.library_paths },
+    ].flatten
+    file.puts "mrb_linker_library_paths_flags=("
+    file.puts contents.map{|lib| "-L#{lib}"}.shelljoin
+    file.puts ")"
+    file.puts ""
+  end
+end
-- 
2.23.1