Add floating-point configuration to CMake (#174)

Change-Id: I4a5ca53c4eb2041c21170b74a9c5d8378612df5e
Signed-off-by: David Vincze <[email protected]>

Signed-off-by: David Vincze <[email protected]>

Author: davidvincze

CMakeLists.txt

@@ -1,3 +1,11 @@
+#-------------------------------------------------------------------------------
+# Copyright (c) 2022-2023, Arm Limited. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+# See BSD-3-Clause license in README.md
+#-------------------------------------------------------------------------------
+
 cmake_minimum_required(VERSION 3.15)
 
 project(qcbor
@@ -14,6 +22,12 @@ set(BUILD_QCBOR_WARN   OFF   CACHE BOOL   "Compile with the warning flags used i
 #    IoT OS's don't support them at all.
 set(BUILD_SHARED_LIBS  OFF   CACHE BOOL   "Build shared libraries instead of static ones")
 
+# Configuration:
+#   Floating-point support (see README.md for more information)
+set(QCBOR_OPT_DISABLE_FLOAT_HW_USE     OFF  CACHE BOOL "Eliminate dependency on FP hardware and FP instructions")
+set(QCBOR_OPT_DISABLE_FLOAT_PREFERRED  OFF  CACHE BOOL "Eliminate support for half-precision and CBOR preferred serialization")
+set(QCBOR_OPT_DISABLE_FLOAT_ALL        OFF  CACHE BOOL "Eliminate floating-point support completely")
+
 if (BUILD_QCBOR_WARN)
     # Compile options applying to all targets in current directory and below
     add_compile_options(-Wall -Wextra -Wpedantic -Wshadow -Wconversion -Wcast-qual)
@@ -37,13 +51,26 @@ target_include_directories(qcbor
         src
 )
 
+target_compile_definitions(qcbor
+    PRIVATE
+        $<$<BOOL:${QCBOR_OPT_DISABLE_FLOAT_HW_USE}>:QCBOR_DISABLE_FLOAT_HW_USE>
+        $<$<BOOL:${QCBOR_OPT_DISABLE_FLOAT_PREFERRED}>:QCBOR_DISABLE_PREFERRED_FLOAT>
+        $<$<BOOL:${QCBOR_OPT_DISABLE_FLOAT_ALL}>:USEFULBUF_DISABLE_ALL_FLOAT>
+)
+
 if (BUILD_SHARED_LIBS)
     target_compile_options(qcbor PRIVATE -Os -fPIC)
 endif()
 
 # The math library is needed for floating-point support.
 # To avoid need for it #define QCBOR_DISABLE_FLOAT_HW_USE
-target_link_libraries(qcbor PRIVATE m)
+if (CMAKE_C_COMPILER_ID STREQUAL "GNU")
+    # Using GCC
+    target_link_libraries(qcbor
+        PRIVATE
+            $<$<NOT:$<BOOL:${QCBOR_OPT_DISABLE_FLOAT_HW_USE}>>:m>
+    )
+endif()
 
 if (NOT BUILD_QCBOR_TEST STREQUAL "OFF")
     add_subdirectory(test)

README.md

@@ -280,7 +280,7 @@ used to reduce object code size and dependency.
 
 See discussion in qcbor_encode.h for other details.
 
-### #define QCBOR_DISABLE_FLOAT_HW_USE
+#### #define QCBOR_DISABLE_FLOAT_HW_USE
 
 This removes dependency on:
 
@@ -359,6 +359,19 @@ In particular, `-mfloat-abi=soft`, disables use of
  hardware instructions for the float and double
  types in C for some architectures.
 
+#### CMake options
+
+If you are using CMake, it can also be used to configure the floating-point
+support. These options can be enabled by adding them to the CMake configuration
+step and setting their value to 'ON' (True). The following table shows the
+available options and the associated #defines.
+
+    | CMake option                      | #define                       |
+    |-----------------------------------|-------------------------------|
+    | QCBOR_OPT_DISABLE_FLOAT_HW_USE    | QCBOR_DISABLE_FLOAT_HW_USE    |
+    | QCBOR_OPT_DISABLE_FLOAT_PREFERRED | QCBOR_DISABLE_PREFERRED_FLOAT |
+    | QCBOR_OPT_DISABLE_FLOAT_ALL       | USEFULBUF_DISABLE_ALL_FLOAT   |
+
 ## Code Size
 
 These are approximate sizes on a 64-bit x86 CPU with the -Os optimization.
@@ -551,4 +564,4 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 ### Copyright for this README
 
 Copyright (c) 2018-2021, Laurence Lundblade. All rights reserved.
-Copyright (c) 2021, Arm Limited. All rights reserved.
+Copyright (c) 2021-2023, Arm Limited. All rights reserved.

test/CMakeLists.txt

@@ -1,3 +1,11 @@
+#-------------------------------------------------------------------------------
+# Copyright (c) 2022-2023, Arm Limited. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+# See BSD-3-Clause license in README.md
+#-------------------------------------------------------------------------------
+
 cmake_minimum_required(VERSION 3.15)
 
 # Validate value of BUILD_QCBOR_TEST config option
@@ -24,12 +32,20 @@ target_include_directories(qcbor_test
         ../inc
 )
 
+target_compile_definitions(qcbor_test
+    PUBLIC
+        $<$<BOOL:${QCBOR_OPT_DISABLE_FLOAT_HW_USE}>:QCBOR_DISABLE_FLOAT_HW_USE>
+        $<$<BOOL:${QCBOR_OPT_DISABLE_FLOAT_PREFERRED}>:QCBOR_DISABLE_PREFERRED_FLOAT>
+        $<$<BOOL:${QCBOR_OPT_DISABLE_FLOAT_ALL}>:USEFULBUF_DISABLE_ALL_FLOAT>
+)
+
 target_link_libraries(qcbor_test
     PRIVATE
         qcbor
         # The math library is needed for floating-point support.
         # To avoid need for it #define QCBOR_DISABLE_FLOAT_HW_USE
-        m
+        # Using GCC
+        $<$<AND:$<STREQUAL:${CMAKE_C_COMPILER_ID},"GNU">,$<NOT:$<BOOL:${QCBOR_OPT_DISABLE_FLOAT_HW_USE}>>>:m>
 )
 
 if (BUILD_QCBOR_TEST STREQUAL "APP")