From 357db6c5e0d571c2e2eb72bfcbdd2fefe72014ca Mon Sep 17 00:00:00 2001
From: Roland Kaufmann <roland.kaufmann@uni.no>
Date: Fri, 5 Jul 2013 12:44:04 +0200
Subject: [PATCH] Add function to detect linker version

The linker that is used (ld vs. gold for instance) is often hidden
when using the compiler as a front-end (to include the correct
runtime libraries).

These functions enables us to probe the linker version and reports
its finding in the log.
---
 cmake/Modules/UseCompVer.cmake | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/cmake/Modules/UseCompVer.cmake b/cmake/Modules/UseCompVer.cmake
index 461898ef..cf0e3772 100644
--- a/cmake/Modules/UseCompVer.cmake
+++ b/cmake/Modules/UseCompVer.cmake
@@ -45,3 +45,34 @@ function (compiler_info)
 	message (STATUS "GNU C++ compiler version: ${version}")
   endif (CMAKE_COMPILER_IS_GNUCXX)
 endfunction (compiler_info)
+
+function (get_ld_version ver_name)
+  # run linker to get the version number. interestingly, this option works
+  # (for our purposes) on all major platforms (Linux, Mac OS X and Windows);
+  # it returns the program version although it may have ended in error
+  exec_program (${CMAKE_LINKER}
+	ARGS "-v"
+	OUTPUT_VARIABLE _version
+	)
+
+  # keep only first line, even on Mac OS X there is no line end
+  list (GET _version 0 _version)
+
+  # format of the version string is platform-specific
+  if (NOT WIN32)
+	if (APPLE)
+	  string (REGEX REPLACE ".*, from Apple (.*\)" "\\1" _version "${_version}")
+	else (APPLE)
+	  # assuming some GNU toolchain now
+	  string (REGEX REPLACE "GNU ([a-zA-Z0-9_]*) \\(.*\\) (.*)" "\\1 \\2" _version "${_version}")
+	endif (APPLE)
+  endif (NOT WIN32)
+
+  # return the string to the caller
+  set (${ver_name} "${_version}" PARENT_SCOPE)
+endfunction (get_ld_version ver_name)
+
+function (linker_info)
+  get_ld_version (version)
+  message (STATUS "Linker: ${version}")
+endfunction (linker_info)