builtin.h does not compile with Arduino IDE g++#43

I am compiling psnip using the Arduino IDE for use on a Teensy, but it results in a compilation error when including `psnip/builtin/builtin.h` in a `.cpp` file. When I include it in a `.c` file it works fine, so that it suggests it has something to do specifically with C++. In another issue I've read that you intend to support C++, but that it's just less well-tested. ``` In file included from C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\test.cpp:2:0: C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h: In function 'unsigned char psnip_intrin_BitScanForward64(long unsigned int*, uint64_t)': C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:636:63: error: '_' was not declared in this scope # define psnip_builtin_ctz64(x) PSNIP_BUILTIN__VARIANT_INT64(_,ctz)(x) ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:1253:61: note: in expansion of macro 'psnip_builtin_ctz64' return PSNIP_BUILTIN_UNLIKELY(Mask == 0) ? 0 : ((*Index = psnip_builtin_ctz64 (Mask)), 1); ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:636:65: error: 'ctz' was not declared in this scope # define psnip_builtin_ctz64(x) PSNIP_BUILTIN__VARIANT_INT64(_,ctz)(x) ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:1253:61: note: in expansion of macro 'psnip_builtin_ctz64' return PSNIP_BUILTIN_UNLIKELY(Mask == 0) ? 0 : ((*Index = psnip_builtin_ctz64 (Mask)), 1); ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:636:68: error: 'PSNIP_BUILTIN__VARIANT_INT64' was not declared in this scope # define psnip_builtin_ctz64(x) PSNIP_BUILTIN__VARIANT_INT64(_,ctz)(x) ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:1253:61: note: in expansion of macro 'psnip_builtin_ctz64' return PSNIP_BUILTIN_UNLIKELY(Mask == 0) ? 0 : ((*Index = psnip_builtin_ctz64 (Mask)), 1); ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h: In function 'unsigned char psnip_intrin_BitScanReverse64(long unsigned int*, uint64_t)': C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:481:63: error: '_' was not declared in this scope # define psnip_builtin_clz64(x) PSNIP_BUILTIN__VARIANT_INT64(_,clz)(x) ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:1287:97: note: in expansion of macro 'psnip_builtin_clz64' return (PSNIP_BUILTIN_UNLIKELY(Mask == 0)) ? 0 : ((*Index = ((sizeof(Mask) * CHAR_BIT) - 1) - psnip_builtin_clz64 (Mask)), 1); ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:481:65: error: 'clz' was not declared in this scope # define psnip_builtin_clz64(x) PSNIP_BUILTIN__VARIANT_INT64(_,clz)(x) ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:1287:97: note: in expansion of macro 'psnip_builtin_clz64' return (PSNIP_BUILTIN_UNLIKELY(Mask == 0)) ? 0 : ((*Index = ((sizeof(Mask) * CHAR_BIT) - 1) - psnip_builtin_clz64 (Mask)), 1); ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:481:68: error: 'PSNIP_BUILTIN__VARIANT_INT64' was not declared in this scope # define psnip_builtin_clz64(x) PSNIP_BUILTIN__VARIANT_INT64(_,clz)(x) ^ C:\Users\ninjoh\AppData\Local\Temp\arduino_build_148318\sketch\psnip/builtin/builtin.h:1287:97: note: in expansion of macro 'psnip_builtin_clz64' return (PSNIP_BUILTIN_UNLIKELY(Mask == 0)) ? 0 : ((*Index = ((sizeof(Mask) * CHAR_BIT) - 1) - psnip_builtin_clz64 (Mask)), 1); ``` sample code: ``` test.cpp --- #include <stdint.h> #include "psnip/builtin/builtin.h" #include "psnip/endian/endian.h" void test_do_nothing(void) { uint16_t be = psnip_endian_be16(200); } ``` How g++ is actually called by the Arduino IDE (newlines added for clarity): ``` "C:\\Users\\ninjoh\\arduino-1.8.13\\hardware\\teensy/../tools/arm/bin/arm-none-eabi-g++" -c -O3 -flto -fno-fat-lto-objects -g -Wall -ffunction-sections -fdata-sections -nostdlib -MMD -fno-exceptions -fpermissive -felide-constructors -std=gnu++14 -Wno-error=narrowing -fno-rtti -mthumb -mcpu=cortex-m4 -fsingle-precision-constant -D__MK20DX256__ -DTEENSYDUINO=153 -DARDUINO=10813 -DARDUINO_TEENSY32 -DF_CPU=24000000 -DUSB_SERIAL_HID -DLAYOUT_US_ENGLISH "-IC:\\Users\\ninjoh\\AppData\\Local\\Temp\\arduino_build_148318/pch" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\hardware\\teensy\\avr\\cores\\teensy3" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\portable\\sketchbook\\libraries\\MFRC522\\src" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\hardware\\teensy\\avr\\libraries\\SPI" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\portable\\sketchbook\\libraries\\Base64\\src" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\portable\\sketchbook\\libraries\\ArduinoBearSSL\\src" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\hardware\\teensy\\avr\\libraries\\EEPROM" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\portable\\sketchbook\\libraries\\EDB" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\hardware\\teensy\\avr\\libraries\\Wire" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\hardware\\teensy\\avr\\libraries\\SD" "-IC:\\Users\\ninjoh\\arduino-1.8.13\\portable\\sketchbook\\libraries\\ArduinoJson\\src" "C:\\Users\\ninjoh\\AppData\\Local\\Temp\\arduino_build_148318\\sketch\\test.cpp" -o "C:\\Users\\ninjoh\\AppData\\Local\\Temp\\arduino_build_148318\\sketch\\test.cpp.o" ```