gnucash master: Link with libm.so on those platforms that require it.

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash/commit/4ee573e2 (commit)
	from  https://github.com/Gnucash/gnucash/commit/43749a94 (commit)



commit 4ee573e23a15691247b509c981258a12bdd49194
Author: John Ralls <jralls at ceridwen.us>
Date:   Mon Jul 6 12:24:49 2020 -0700

    Link with libm.so on those platforms that require it.

diff --git a/common/cmake_modules/CMakeLists.txt b/common/cmake_modules/CMakeLists.txt
index 115c90fd5..e25f806b2 100644
--- a/common/cmake_modules/CMakeLists.txt
+++ b/common/cmake_modules/CMakeLists.txt
@@ -1,7 +1,7 @@
 
 set(cmake_FILES
   GncAddGSchemaTargets.cmake GncAddSchemeTargets.cmake
-  GncAddSwigCommand.cmake GncAddTest.cmake
+  GncAddSwigCommand.cmake GncAddTest.cmake GncFindLibm.cmake
   MacroAddSourceFileCompileFlags.cmake MacroAppendForeach.cmake
   MakeDist.cmake MakeDistFiles.cmake MakeDistCheck.cmake
   )
diff --git a/common/cmake_modules/GncFindLibm.cmake b/common/cmake_modules/GncFindLibm.cmake
new file mode 100644
index 000000000..ab29df95c
--- /dev/null
+++ b/common/cmake_modules/GncFindLibm.cmake
@@ -0,0 +1,46 @@
+# Copied & modified from https://android.googlesource.com/platform/external/eigen/+/master/cmake/FindStandardMathLibrary.cmake
+# Copyright (c) 2010 Benoit Jacob <jacob.benoit.1 at gmail.com>
+# Redistribution and use is allowed according to the terms of the 2-clause BSD license.
+# For details see the accompanying COPYING-CMAKE-SCRIPTS file.
+
+#Detect whether this platform requires libm for pow().
+
+include(CheckCXXSourceCompiles)
+macro (gnc_check_standard_math_library)
+  set(find_standard_math_library_test_program
+"
+#include <math.h>
+int main(int argc, char** argv)
+{
+    double foo = pow(2.0, 2.0);
+    return foo == 4.0;
+}"
+  )
+
+  set(CMAKE_REQUIRED_FLAGS "")
+  set(CMAKE_REQUIRED_LIBRARIES "")
+  check_c_source_compiles(
+    "${find_standard_math_library_test_program}"
+    standard_math_library_linked_to_automatically
+    )
+  if(standard_math_library_linked_to_automatically)
+    # the test program linked successfully without any linker flag.
+    set(STANDARD_MATH_LIBRARY "")
+    set(STANDARD_MATH_LIBRARY_FOUND TRUE)
+  else()
+    # the test program did not link successfully without any linker flag.
+    # Try again with standard name 'm' for the standard math library.
+    set(CMAKE_REQUIRED_LIBRARIES "m")
+    check_c_source_compiles(
+      "${find_standard_math_library_test_program}"
+      standard_math_library_linked_to_as_m)
+    if(standard_math_library_linked_to_as_m)
+      # the test program linked successfully when linking to the 'm' library
+      set(STANDARD_MATH_LIBRARY "m")
+      set(STANDARD_MATH_LIBRARY_FOUND TRUE)
+    else()
+      # the test program still doesn't link successfully
+      set(STANDARD_MATH_LIBRARY_FOUND FALSE)
+    endif()
+  endif()
+endmacro()
diff --git a/libgnucash/app-utils/CMakeLists.txt b/libgnucash/app-utils/CMakeLists.txt
index 4cfa65a35..2cc9c82f1 100644
--- a/libgnucash/app-utils/CMakeLists.txt
+++ b/libgnucash/app-utils/CMakeLists.txt
@@ -1,6 +1,9 @@
 # NB: Unit tests which require GSchemas should be made conditional on COMPILE_GSCHEMAS.
 add_subdirectory(test)
 add_subdirectory(mocks)
+
+include (GncFindLibm)
+
 # Build the library
 
 set (app_utils_noinst_HEADERS
@@ -67,10 +70,15 @@ set (app_utils_SOURCES
   gnc-ui-util.c
   gnc-ui-balances.c
   option-util.c
-)
+  )
 
 set_source_files_properties (${app_utils_SOURCES} PROPERTIES OBJECT_DEPENDS ${CONFIG_H})
 
+gnc_check_standard_math_library()
+if (NOT STANDARD_MATH_LIBRARY_FOUND)
+  message(FATAL_ERROR "An implementation of the standard C function pow() is required and is supported neither by the C runtime nor libm.so.")
+endif()
+
 set(app_utils_ALL_SOURCES ${app_utils_SOURCES} ${app_utils_HEADERS} ${app_utils_noinst_HEADERS})
 set(app_utils_ALL_LIBRARIES
     gnc-engine
@@ -78,7 +86,10 @@ set(app_utils_ALL_LIBRARIES
     gnucash-guile
     ${GIO_LDFLAGS}
     ${LIBXML2_LDFLAGS}
-    ${LIBXSLT_LDFLAGS})
+    ${LIBXSLT_LDFLAGS}
+    ${STANDARD_MATH_LIBRARY}
+)
+
 set(app_utils_ALL_INCLUDES
     ${CMAKE_CURRENT_SOURCE_DIR}/calculation
     ${GIO_INCLUDE_DIRS}



Summary of changes:
 common/cmake_modules/CMakeLists.txt    |  2 +-
 common/cmake_modules/GncFindLibm.cmake | 46 ++++++++++++++++++++++++++++++++++
 libgnucash/app-utils/CMakeLists.txt    | 15 +++++++++--
 3 files changed, 60 insertions(+), 3 deletions(-)
 create mode 100644 common/cmake_modules/GncFindLibm.cmake