From bb6a97a8f3e4e046442eaf8814b30d9c9995bfd2 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 30 Aug 2016 16:50:01 +0200
Subject: Build infrastructure update

---
 hello/buildfile | 23 +++++++++++++++++++----
 hello/export    | 36 ++++++++++++++++++++++++++++++++++++
 hello/hello     | 21 +++++++++++++++++++--
 hello/hello.cxx |  5 ++---
 4 files changed, 76 insertions(+), 9 deletions(-)
 create mode 100644 hello/export

(limited to 'hello')

diff --git a/hello/buildfile b/hello/buildfile
index c18fa98..8807f1b 100644
--- a/hello/buildfile
+++ b/hello/buildfile
@@ -1,11 +1,26 @@
-import libs = libformat%lib{format}
-import libs += libprint%lib{print}
+import int_libs = libformat%lib{format}
+import imp_libs = libprint%lib{print}
 
-lib{hello}: {hxx cxx}{hello} $libs
+lib{hello}: {hxx cxx}{hello} hxx{export} $imp_libs $int_libs
+
+# For pre-releases use the complete version to make sure they cannot be used
+# in place of another pre-release or the final version.
+#
+if $abi_prerelease
+  lib{hello}: bin.lib.version = @-$version
+else
+  lib{hello}: bin.lib.version = @-$abi_major.$abi_minor
 
 cxx.poptions += -I$src_root
+obja{*}: cxx.poptions += -DLIBHELLO_STATIC_BUILD
+objs{*}: cxx.poptions += -DLIBHELLO_SHARED_BUILD
+
 lib{hello}: cxx.export.poptions = -I$src_root
+liba{hello}: cxx.export.poptions += -DLIBHELLO_STATIC
+libs{hello}: cxx.export.poptions += -DLIBHELLO_SHARED
+
+lib{hello}: cxx.export.libs = $int_libs
 
 # Install into the hello/ subdirectory of, say, /usr/include/.
 #
-install.include = $install.include/hello
+install.include = $install.include/hello/
diff --git a/hello/export b/hello/export
new file mode 100644
index 0000000..18f4968
--- /dev/null
+++ b/hello/export
@@ -0,0 +1,36 @@
+// file: hello/export -*- C++ -*-
+
+#pragma once
+
+// Normally we don't export class templates (but do complete specializations),
+// inline functions, and classes with only inline member functions. Exporting
+// classes that inherit from non-exported/imported bases (e.g., std::string)
+// will end up badly. The only known workarounds are to not inherit or to not
+// export. Also, MinGW GCC doesn't like seeing non-exported function being
+// used before their inline definition. The workaround is to reorder code. In
+// the end it's all trial and error.
+
+#if defined(LIBHELLO_STATIC)         // Using static.
+#  define LIBHELLO_EXPORT
+#elif defined(LIBHELLO_STATIC_BUILD) // Building static.
+#  define LIBHELLO_EXPORT
+#elif defined(LIBHELLO_SHARED)       // Using shared.
+#  ifdef _WIN32
+#    define LIBHELLO_EXPORT __declspec(dllimport)
+#  else
+#    define LIBHELLO_EXPORT
+#  endif
+#elif defined(LIBHELLO_SHARED_BUILD) // Building shared.
+#  ifdef _WIN32
+#    define LIBHELLO_EXPORT __declspec(dllexport)
+#  else
+#    define LIBHELLO_EXPORT
+#  endif
+#else
+// If none of the above macros are defined, then we assume we are being used
+// by some third-party build system that cannot/doesn't signal the library
+// type. Note that this fallback works for both static and shared but in case
+// of shared will be sub-optimal compared to having dllimport.
+//
+#  define LIBHELLO_EXPORT            // Using static or shared.
+#endif
diff --git a/hello/hello b/hello/hello
index 4f85114..75a47a0 100644
--- a/hello/hello
+++ b/hello/hello
@@ -4,8 +4,25 @@
 
 #include <string>
 
+#include <format/format>
+
+#include <hello/export>
+
 namespace hello
 {
-  void
-  say (const std::string& name);
+  // If you compare this interface to version 1.0, then you will notice that
+  // while it is API/source-compatible (the signature of say() is unchanged)
+  // it is not ABI/binary-compatible (say() is now inline).
+  //
+  // Notice also that inline say() calls format() which means libformat is an
+  // interface dependency of libhello.
+
+  LIBHELLO_EXPORT void
+  say_formatted (const std::string& message);
+
+  inline void
+  say (const std::string& name)
+  {
+    say_formatted (format ("Hello", name));
+  }
 }
diff --git a/hello/hello.cxx b/hello/hello.cxx
index 46d9f6e..8fdd5a6 100644
--- a/hello/hello.cxx
+++ b/hello/hello.cxx
@@ -2,7 +2,6 @@
 
 #include <hello/hello>
 
-#include <format/format>
 #include <print/print>
 
 using namespace std;
@@ -10,8 +9,8 @@ using namespace std;
 namespace hello
 {
   void
-  say (const string& n)
+  say_formatted (const string& m)
   {
-    print (format ("Hello", n));
+    print (m);
   }
 }
-- 
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