Start using exceptions.

CMakeLists.txt

@@ -19,6 +19,7 @@ set(SOURCE_FILES
  src/mavlink.cpp
  src/outputs.cpp
  src/pulse_processor.cpp
+ src/platform.cpp
 
  src/primitives/timestamp.cpp
  src/primitives/string_utils.cpp

notes.md

@@ -33,3 +33,13 @@ https://google.github.io/styleguide/cppguide.html
 ### Git submodule management
  * Update submodules to latest on branches/tags: `git submodule update --remote`
  * When changing .gitmodules, do `git submodule sync`
+
+### GCC Headers search for #include <..>
+
+ /usr/local/Caskroom/gcc-arm-embedded/6_2-2016q4,20161216/gcc-arm-none-eabi-6_2-2016q4
+ /arm-none-eabi/include/c++/6.2.1
+ /arm-none-eabi/include/c++/6.2.1/arm-none-eabi
+ /arm-none-eabi/include/c++/6.2.1/backward
+ /lib/gcc/arm-none-eabi/6.2.1/include
+ /lib/gcc/arm-none-eabi/6.2.1/include-fixed
+ /arm-none-eabi/include

src/platform.cpp

@@ -0,0 +1,62 @@
+#include <exception>
+#include <assert.h>
+#include <stdlib.h>
+
+// This file contains support functions that make it possible to use C++ exceptions and other niceties 
+// in a meaningful way on Teensy.
+// See https://andriidevel.blogspot.com/2016/05/size-cost-of-c-exception-handling-on.html for some tricks used.
+
+// NOTE: gcc-arm-embedded uses 'newlib' as stdlib. To be properly used, newlib needs several "Syscall" functions
+// to be implemented, see https://sourceware.org/newlib/libc.html#Syscalls .
+// For Teensy, some of them are defined in teensy3/mk20dx128.c but we need to 
+
+
+// ==== 1. Termination ================================
+
+// abort() is a C stdlib function to do an abnormal program termination.
+// It's being called for example when exception handling mechanisms themselves fail. 
+// It's not defined by default, so we need to implement it.
+void abort() {
+ // TODO: Write to eeprom.
+ while(1);
+}
+
+// terminate_handler is called on std::terminate() and handles uncaught exceptions, exception-in-exceptions, etc.
+// We install it statically below (__cxxabiv1::__terminate_handler) to avoid linking with default GCC 
+// __verbose_terminate_handler, which adds 30kb of code.
+// See also: https://gcc.gnu.org/onlinedocs/libstdc++/manual/termination.html
+// https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/libsupc%2B%2B/vterminate.cc#L44
+void terminate_handler() {
+ // TODO: Get exception name and write to eeprom.
+ while(1);
+}
+
+namespace __cxxabiv1 { 
+ std::terminate_handler __terminate_handler = terminate_handler; // Default terminate handler for gcc c++ impl.
+}
+
+// TODO: We might want to re-define _exit() and __cxa_pure_virtual() as well to provide meaningful actions.
+
+
+// ==== 2. Memory ================================
+
+// Low-leve _sbrk() syscall to allocate memory is defined in teensy3/mk20dx128.c and very simple - just moves 
+// __brkval, current top of the heap.
+// malloc() uses _sbrk().
+// Teensy defines basic "operator new()", but it's too simple for our case, so we use standard one instead.
+
+// Nice lib to get memory stats: https://github.com/michaeljball/RamMonitor
+// Or, use standard interface mallinfo(); (uordblks = bytes in use, fordblks = bytes free.)
+
+
+// ==== 3. Assertions ================================
+
+// assert() macro in debug mode is defined to call __assert_func when assertion fails. 
+// We must redefine it statically to avoid linking to additional 15kb of code.
+// Default implementation: https://github.com/bminor/newlib/blob/master/newlib/libc/stdlib/assert.c#L53
+void __assert_func(const char *file, int line, const char *function_name, const char *expression) {
+ // TODO: Write to EEPROM.
+ while(1);
+}
+
+

teensy-arm.toolchain.cmake

@@ -58,19 +58,19 @@ set_property(CACHE TEENSY_USB_MODE PROPERTY STRINGS SERIAL HID SERIAL_HID MIDI R
 
 set(TARGET_FLAGS "-mcpu=cortex-m4 -mthumb -mfp16-format=ieee")
 set(OPTIMIZE_FLAGS "-O2" CACHE STRING "Optimization flags") # Remember to reset cache and rebuild cmake when changing this.
-set(CMAKE_C_FLAGS "${OPTIMIZE_FLAGS} -Wall -nostdlib -ffunction-sections -fdata-sections ${TARGET_FLAGS}" CACHE STRING "C/C++ flags")
-set(CMAKE_CXX_FLAGS "${CMAKE_C_FLAGS} -std=gnu++14 -fno-exceptions -fno-rtti -felide-constructors -fsingle-precision-constant -Woverloaded-virtual" CACHE STRING "c++ flags")
+set(CMAKE_C_FLAGS "${OPTIMIZE_FLAGS} -Wall -ffunction-sections -fdata-sections ${TARGET_FLAGS}" CACHE STRING "C/C++ flags")
+set(CMAKE_CXX_FLAGS "${CMAKE_C_FLAGS} -std=gnu++14 -fno-rtti -fsingle-precision-constant -Woverloaded-virtual" CACHE STRING "C++ flags")
+
+set(CMAKE_C_FLAGS_RELEASE "-DNDEBUG" CACHE STRING "" FORCE) # Don't do -O3 because it increases the size. Just remove asserts.
+set(CMAKE_CXX_FLAGS_RELEASE "-DNDEBUG" CACHE STRING "" FORCE)
 
 link_libraries(m)
 set(LINKER_FLAGS "--gc-sections,--relax,--defsym=__rtc_localtime=0" CACHE STRING "Ld flags")
 set(CXX_LINKER_FLAGS "${OPTIMIZE_FLAGS} -Wl,${LINKER_FLAGS} ${TARGET_FLAGS} -T${TEENSY_ROOT}/mk20dx256.ld")
 
-set(CMAKE_SHARED_LINKER_FLAGS "${CXX_LINKER_FLAGS}" CACHE STRING "Linker flags" FORCE)
-set(CMAKE_MODULE_LINKER_FLAGS "${CXX_LINKER_FLAGS}" CACHE STRING "Linker flags" FORCE)
-set(CMAKE_EXE_LINKER_FLAGS "${CXX_LINKER_FLAGS}" CACHE STRING "Linker flags" FORCE)
-
-# Don't pass regular CMAKE_CXX_FLAGS because that causes undefined symbols
-set(CMAKE_CXX_LINK_EXECUTABLE "<CMAKE_CXX_COMPILER> <CMAKE_CXX_LINK_FLAGS> <LINK_FLAGS> <OBJECTS> -o <TARGET> <LINK_LIBRARIES>")
+set(CMAKE_SHARED_LINKER_FLAGS "${CXX_LINKER_FLAGS}" CACHE STRING "Shared Linker flags" FORCE)
+set(CMAKE_MODULE_LINKER_FLAGS "${CXX_LINKER_FLAGS}" CACHE STRING "Module Linker flags" FORCE)
+set(CMAKE_EXE_LINKER_FLAGS "${CXX_LINKER_FLAGS}" CACHE STRING "Executable Linker flags" FORCE)
 
 
 add_definitions("-DARDUINO=${ARDUINO_VERSION}")
@@ -79,6 +79,7 @@ add_definitions("-D__${TEENSY_MODEL}__")
 add_definitions("-DUSB_${TEENSY_USB_MODE}")
 add_definitions("-DF_CPU=${TEENSY_FREQUENCY}000000")
 add_definitions("-DLAYOUT_US_ENGLISH")
+add_definitions("-DNEW_H") # Don't include new.h header as it defines non-standard operator new().
 add_definitions("-MMD")
 
 # Define target for the Teensy 'core' library.
@@ -88,6 +89,7 @@ if (NOT TARGET TeensyCore AND NOT ${CMAKE_SOURCE_DIR} MATCHES "CMakeTmp")
  file(GLOB TEENSY_C_CORE_FILES "${TEENSY_ROOT}/*.c")
  list(REMOVE_ITEM TEENSY_C_CORE_FILES "${TEENSY_ROOT}/math_helper.c") # legacy cmsis file - not needed anyway.
  file(GLOB TEENSY_CXX_CORE_FILES "${TEENSY_ROOT}/*.cpp")
+ list(REMOVE_ITEM TEENSY_CXX_CORE_FILES "${TEENSY_ROOT}/new.cpp") # Don't use non-standard operator new.
  add_library(TeensyCore ${TEENSY_C_CORE_FILES} ${TEENSY_CXX_CORE_FILES})
  link_libraries(TeensyCore)
  include_directories(${TEENSY_ROOT})