SERVER-3364 Add macros for putting visibility and calling convention declarations on declarations.

Also SERVER-5650.

MONGO_COMPILER_API_EXPORT Puts the "export visibility" declaration on a type,
    function or variable.

MONGO_COMPILER_API_IMPORT Puts the "import from library" declaration on a type,
    function or variable.

MONGO_COMPILER_API_CALLING_CONVENTION Labels a function declaration with its
    calling convention.

3 files changed, 67 insertions, 1 deletions

diff --git a/src/mongo/platform/compiler.h b/src/mongo/platform/compiler.h
index 9bb166e8f60..7a0a18495b4 100644
--- a/src/mongo/platform/compiler.h
+++ b/src/mongo/platform/compiler.h
@@ -27,7 +27,7 @@
  *   Instructs the compiler that the decorated function will not return through the normal return
  *   path.
  *
- *   Correct: void MONGO_COMPILER_NORETURN myAbortFunction();
+ *   Correct: MONGO_COMPILER_NORETURN void myAbortFunction();
  *
  *
  * MONGO_COMPILER_VARIABLE_UNUSED
@@ -71,6 +71,40 @@
  *
  *   Incorrect:
  *     int MONGO_COMPILER_ALIGN_VARIABLE(16) a, b;
+ *
+ *
+ * MONGO_COMPILER_API_EXPORT
+ *
+ *   Instructs the compiler to label the given type, variable or function as part of the
+ *   exported interface of the library object under construction.
+ *
+ *   Correct:
+ *       MONGO_COMPILER_API_EXPORT int globalSwitch;
+ *       class MONGO_COMPILER_API_EXPORT ExportedType { ... };
+ *       MONGO_COMPILER_API_EXPORT SomeType exportedFunction(...);
+ *
+ *   NOTE: Rather than using this macro directly, one typically declares another macro named for the
+ *   library, which is conditionally defined to either MONGO_COMIPLER_API_EXPORT or
+ *   MONGO_COMPILER_API_IMPORT based on whether the compiler is currently building the library or
+ *   building an object that depends on the library, respectively.  For example, MONGO_CLIENT_API
+ *   might be defined to MONGO_COMPILER_API_EXPORT when building the MongoDB shared library, and to
+ *   MONGO_COMPILER_API_IMPORT when building an application that links against the shared library.
+ *
+ *
+ * MONGO_COMPILER_API_IMPORT
+ *
+ *   Instructs the compiler to label the given type, variable or function as imported
+ *   from another library, and not part of the library object under construction.
+ *
+ *   Same correct/incorrect usage as for MONGO_COMPILER_API_EXPORT.
+ *
+ *
+ * MONGO_COMPILER_API_CALLING_CONVENTION
+ *
+ *    Explicitly decorates a function declaration the api calling convention used for
+ *    shared libraries.
+ *
+ *    Same correct/incorrect usage as for MONGO_COMPILER_API_EXPORT.
  */
 
 #if defined(_MSC_VER)
diff --git a/src/mongo/platform/compiler_gcc.h b/src/mongo/platform/compiler_gcc.h
index 84d2a8f52d5..14540c13eb3 100644
--- a/src/mongo/platform/compiler_gcc.h
+++ b/src/mongo/platform/compiler_gcc.h
@@ -29,3 +29,23 @@
 #define MONGO_COMPILER_ALIGN_TYPE(ALIGNMENT) __attribute__(( __aligned__(ALIGNMENT) ))
 
 #define MONGO_COMPILER_ALIGN_VARIABLE(ALIGNMENT) __attribute__(( __aligned__(ALIGNMENT) ))
+
+// NOTE(schwerin): These visibility and calling-convention macro definitions assume we're not using
+// GCC/CLANG to target native Windows. If/when we decide to do such targeting, we'll need to change
+// compiler flags on Windows to make sure we use an appropriate calling convention, and configure
+// MONGO_COMPILER_API_EXPORT, MONGO_COMPILER_API_IMPORT and MONGO_COMPILER_API_CALLING_CONVENTION
+// correctly.  I believe "correctly" is the following:
+//
+// #ifdef _WIN32
+// #define MONGO_COMIPLER_API_EXPORT __attribute__(( __dllexport__ ))
+// #define MONGO_COMPILER_API_IMPORT __attribute__(( __dllimport__ ))
+// #ifdef _M_IX86
+// #define MONGO_COMPILER_API_CALLING_CONVENTION __attribute__((__cdecl__))
+// #else
+// #define MONGO_COMPILER_API_CALLING_CONVENTION
+// #endif
+// #else ... fall through to the definitions below.
+
+#define MONGO_COMPILER_API_EXPORT __attribute__(( __visibility__("default") ))
+#define MONGO_COMPILER_API_IMPORT
+#define MONGO_COMPILER_API_CALLING_CONVENTION
diff --git a/src/mongo/platform/compiler_msvc.h b/src/mongo/platform/compiler_msvc.h
index a2207009785..1155e7d6edd 100644
--- a/src/mongo/platform/compiler_msvc.h
+++ b/src/mongo/platform/compiler_msvc.h
@@ -29,3 +29,15 @@
 #define MONGO_COMPILER_ALIGN_TYPE(ALIGNMENT) __declspec( align( ALIGNMENT ) )
 
 #define MONGO_COMPILER_ALIGN_VARIABLE(ALIGNMENT) __declspec( align( ALIGNMENT ) )
+
+#define MONGO_COMPILER_API_EXPORT __declspec(dllexport)
+#define MONGO_COMPILER_API_IMPORT __declspec(dllimport)
+
+#ifdef _M_IX86
+// 32-bit x86 supports multiple of calling conventions.  We build supporting the cdecl convention
+// (most common).  By labeling our exported and imported functions as such, we do a small favor to
+// 32-bit Windows developers.
+#define MONGO_COMPILER_API_CALLING_CONVENTION __cdecl
+#else
+#define MONGO_COMPILER_API_CALLING_CONVENTION
+#endif