[ruby/yarp] Document building, more macro changes

https://github.com/ruby/yarp/commit/4214f262d2

docs/building.md

@@ -0,0 +1,26 @@
+# Building
+
+The following describes how to build YARP from source.
+
+## Common
+
+All of the source files match `src/**/*.c` and all of the headers match `include/**/*.h`.
+
+The following flags should be used to compile YARP:
+
+* `-std=c99` - Use the C99 standard
+* `-Wall -Wconversion -Wextra -Wpedantic -Wundef` - Enable the warnings we care about
+* `-Werror` - Treat warnings as errors
+* `-fvisibility=hidden` - Hide all symbols by default
+
+The following flags can be used to compile YARP:
+
+* `-DHAVE_MMAP` - Should be passed if the system has the `mmap` function
+* `-DHAVE_SNPRINTF` - Should be passed if the system has the `snprintf` function
+
+## Shared
+
+If you want to build YARP as a shared library and link against it, you should compile with:
+
+* `-fPIC -shared` - Compile as a shared library
+* `-DYP_EXPORT_SYMBOLS` - Export the symbols (by default nothing is exported)

lib/yarp/yarp.gemspec

@@ -20,6 +20,7 @@ Gem::Specification.new do |spec|
     "config.h.in",
     "config.yml",
     "configure",
+    "docs/building.md",
     "docs/configuration.md",
     "docs/design.md",
     "docs/encoding.md",

yarp/defines.h

@@ -12,18 +12,16 @@
 #include <string.h>
 
 // YP_EXPORTED_FUNCTION
-#if defined(_WIN32)
-#   define YP_EXPORTED_FUNCTION __declspec(dllexport) extern
-#elif defined(YP_EXPORT_SYMBOLS)
-#   ifndef YP_EXPORTED_FUNCTION
-#       ifndef RUBY_FUNC_EXPORTED
-#           define YP_EXPORTED_FUNCTION __attribute__((__visibility__("default"))) extern
+#ifndef YP_EXPORTED_FUNCTION
+#   ifdef YP_EXPORT_SYMBOLS
+#       ifdef _WIN32
+#          define YP_EXPORTED_FUNCTION __declspec(dllexport) extern
 #       else
-#           define YP_EXPORTED_FUNCTION RUBY_FUNC_EXPORTED
+#          define YP_EXPORTED_FUNCTION __attribute__((__visibility__("default"))) extern
 #       endif
+#   else
+#       define YP_EXPORTED_FUNCTION
 #   endif
-#else
-#   define YP_EXPORTED_FUNCTION
 #endif
 
 // YP_ATTRIBUTE_UNUSED