ESP8266 NONOS SDK: How to compile C++ code? - esp8266

Question

ESP8266 NONOS SDK: How to compile C++ code?
I'm somehow not able to compile C++ code using the ESP8266 NONOS SDK.
I use the gen_misc.sh-script to configure and compile the program,
but it outputs the following error:
start...
make[1]: Entering directory '/repos/esp/ESP8266_NONOS_SDK/diplomarbeit-firmware/user'
xtensa-lx106-elf-g++ -Os -g -Wpointer-arith -Wundef -Werror -Wl,-EL -fno-inline-functions -nostdlib -mlongcalls -mtext-section-literals -ffunction-sections -fdata-sections -fno-builtin-printf -DICACHE_FLASH -DSPI_FLASH_SIZE_MAP=3 -I include -I ./ -I ../../include/ets -I ../include -I ../../include -I ../../include/eagle -I ../../driver_lib/include -o .output/eagle/debug/obj/user_main.o -c user_main.cpp
xtensa-lx106-elf-ar ru .output/eagle/debug/lib/libuser.a .output/eagle/debug/obj/user_main.o
make[1]: Leaving directory '/repos/esp/ESP8266_NONOS_SDK/diplomarbeit-firmware/user'
xtensa-lx106-elf-gcc -L../lib -nostdlib -T../ld/eagle.app.v6.ld -Wl,--no-check-sections -Wl,--gc-sections -u call_user_start -Wl,-static -Wl,--start-group -lc -lgcc -lhal -lphy -lpp-lnet80211 -llwip -lwpa -lcrypto -lmain -ldriver user/.output/eagle/debug/lib/libuser.a -Wl,--end-group -o .output/eagle/debug/image/eagle.app.v6.out
../lib/libmain.a(app_main.o): In function `user_uart_wait_tx_fifo_empty':
(.irom0.text+0x6a0): undefined reference to `user_pre_init'
../lib/libmain.a(app_main.o): In function `user_uart_wait_tx_fifo_empty':
(.irom0.text+0x6b8): undefined reference to `user_init'
../lib/libmain.a(app_main.o): In function `flash_data_check':
(.irom0.text+0x718): undefined reference to `user_pre_init'
../lib/libmain.a(app_main.o): In function `flash_data_check':
(.irom0.text+0xac1): undefined reference to `user_init'
collect2: error: ld returned 1 exit status
../Makefile:398: recipe for target '.output/eagle/debug/image/eagle.app.v6.out' failed
make: *** [.output/eagle/debug/image/eagle.app.v6.out] Error 1
My code looks like that:
user_main.cpp
#include "user_interface.h"
#include "osapi.h"
#include "partition.h"
void ICACHE_FLASH_ATTR user_pre_init ()
{
// register partition table here
if (!system_partition_table_regist(partition_table,
sizeof(partition_table) / sizeof(partition_table[0]),
SPI_FLASH_SIZE_MAP))
{
os_printf("FAIL TO REGISTER PARTITION TABLE");
while (1) {}
}
}
class MyClass {
};
void user_init ()
{
os_printf("Hello world!\n");
}
I really don't know how to fix this problem.

Answer 1

The header files you are including are C header files, not C++. The C++ compiler will mangle the function names, leading to the above error you see. You need to wrap them in an extern block like this to tell the compiler not to mangle them:
extern "C" {
#include "user_interface.h"
#include "osapi.h"
#include "partition.h"
}