cmake: strip file full path to save the code size

Cmake build provide absolute paths to compile files. If __FILE__
macros are used in the source code(ASSERT), the binary will be occupied
by many invalid paths.
This saves some memory, stops leaking user locations in binaries, makes
failure logs more deterministic and most importantly makes builds more
deterministic.
Debuggers usually have a path mapping feature to ensure the files are
still found.

Test config sabre-6quad/citest:

Before:
$ size build/nuttx
   text	   data	    bss	    dec	    hex	filename
 279309	    908	  13652	 293869	  47bed	build/nuttx

After:
$ size build/nuttx
   text	   data	    bss	    dec	    hex	filename
 269313	    908	  13652	 283873	  454e1	build/nuttx

Signed-off-by: chao an <[email protected]>

CMakeLists.txt

@@ -173,6 +173,7 @@ if(NOT EXISTS "${NUTTX_APPS_DIR}")
   message(FATAL_ERROR "Application directory ${NUTTX_APPS_DIR} is not found")
 endif()
 
+get_filename_component(NUTTX_APPS_DIR ${NUTTX_APPS_DIR} ABSOLUTE)
 get_filename_component(apps_dir ${NUTTX_APPS_DIR} NAME)
 set(NUTTX_APPS_BINDIR "${CMAKE_BINARY_DIR}/${apps_dir}")
 
@@ -513,6 +514,21 @@ if(CONFIG_NDEBUG)
   add_compile_options(-DNDEBUG)
 endif()
 
+# Cmake build provide absolute paths to compile files. If __FILE__ macros are
+# used in the source code(ASSERT), the binary will be occupied by many invalid
+# paths. If the compiler support preprocessing files and expand the "__FILE__"
+# and "__BASE_FILE__" macros as if the files resided in directory new instead.
+# This saves some memory, stops leaking user locations in binaries, makes
+# failure logs more deterministic and most importantly makes builds more
+# deterministic. Debuggers usually have a path mapping feature to ensure the
+# files are still found.
+if(CONFIG_OUTPUT_STRIP_PATHS)
+  add_compile_options(-fmacro-prefix-map=${NUTTX_DIR}=)
+  add_compile_options(-fmacro-prefix-map=${NUTTX_APPS_DIR}=)
+  add_compile_options(-fmacro-prefix-map=${NUTTX_BOARD_ABS_DIR}=)
+  add_compile_options(-fmacro-prefix-map=${NUTTX_CHIP_ABS_DIR}=)
+endif()
+
 add_definitions(-D__NuttX__)
 
 set_property(

Kconfig

@@ -447,6 +447,21 @@ config DFU_PID
 	hex "PID to use for DFU image"
 
 endif # DFU_BINARY
+
+config OUTPUT_STRIP_PATHS
+	bool "Strip absolute paths from binaries"
+	default y
+	depends on ARCH_TOOLCHAIN_GNU
+	---help---
+	  Cmake build provide absolute paths to compile files. If __FILE__
+	  macros are used in the source code(ASSERT), the binary will be occupied
+	  by many invalid paths.
+	  This saves some memory, stops leaking user locations in binaries, makes
+	  failure logs more deterministic and most importantly makes builds more
+	  deterministic.
+	  Debuggers usually have a path mapping feature to ensure the files are
+	  still found.
+
 endmenu # Binary Output Formats
 
 menu "Customize Header Files"