Merged gsoc-ssh branch. Closes #910

libssh2/cmake/CheckFunctionExistsMayNeedLibrary.cmake

@@ -0,0 +1,81 @@
+# Copyright (c) 2014 Alexander Lamaison <alexander.lamaison@gmail.com>
+#
+# Redistribution and use in source and binary forms,
+# with or without modification, are permitted provided
+# that the following conditions are met:
+#
+#   Redistributions of source code must retain the above
+#   copyright notice, this list of conditions and the
+#   following disclaimer.
+#
+#   Redistributions in binary form must reproduce the above
+#   copyright notice, this list of conditions and the following
+#   disclaimer in the documentation and/or other materials
+#   provided with the distribution.
+#
+#   Neither the name of the copyright holder nor the names
+#   of any other contributors may be used to endorse or
+#   promote products derived from this software without
+#   specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+# CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+# INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+# NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
+# USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+# OF SUCH DAMAGE.
+
+
+# - check_function_exists_maybe_need_library(<function> <var> [lib1 ... libn])
+#
+# Check if function is available for linking, first without extra libraries, and
+# then, if not found that way, linking in each optional library as well.  This
+# function is similar to autotools AC_SEARCH_LIBS.
+#
+# If the function if found, this will define <var>.
+#
+# If the function was only found by linking in an additional library, this
+# will define NEED_LIB_LIBX, where LIBX is the one of lib1 to libn that
+# makes the function available, in uppercase.
+#
+# The following variables may be set before calling this macro to
+# modify the way the check is run:
+#
+#  CMAKE_REQUIRED_FLAGS = string of compile command line flags
+#  CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
+#  CMAKE_REQUIRED_INCLUDES = list of include directories
+#  CMAKE_REQUIRED_LIBRARIES = list of libraries to link
+#
+
+include(CheckFunctionExists)
+include(CheckLibraryExists)
+
+function(check_function_exists_may_need_library function variable)
+
+  check_function_exists(${function} ${variable})
+
+  if(NOT ${variable})
+    foreach(lib ${ARGN})
+      string(TOUPPER ${lib} UP_LIB)
+      # Use new variable to prevent cache from previous step shortcircuiting
+      # new test
+      check_library_exists(${lib} ${function} "" HAVE_${function}_IN_${lib})
+      if(HAVE_${function}_IN_${lib})
+	set(${variable} 1 CACHE INTERNAL
+	  "Function ${function} found in library ${lib}")
+	set(NEED_LIB_${UP_LIB} 1 CACHE INTERNAL
+	  "Need to link ${lib}")
+	break()
+      endif()
+    endforeach()
+  endif()
+
+endfunction()