build the sdk demo error,sdk 1.4.0,demo - ESP8266_IOT_PLATFORM-master

[rpj]

hi：
q：used the rtos sdk version 1.4.0,get the demo code for iot - ESP8266_IOT_PLATFORM-master,then build the project,but fail.
=======================log===============
make[1]:正在离开目录 `/home/ppt/t/build/esp8266/ESP8266_RTOS_SDK/examples/ESP8266_IOT_PLATFORM-master/libesphttpd'
xtensa-lx106-elf-gcc -L/home/ppt/t/build/esp8266/ESP8266_RTOS_SDK/examples/ESP8266_IOT_PLATFORM-master/../..//lib -Wl,--gc-sections -nostdlib -T/home/ppt/t/build/esp8266/ESP8266_RTOS_SDK/examples/ESP8266_IOT_PLATFORM-master/../..//ld/eagle.app.v6.new.2048.ld -Wl,--no-check-sections -u call_user_start -Wl,-static -Wl,--start-group -lminic -lgcc -lhal -lphy -lpp -lnet80211 -lcrypto -lwpa -lmain -lfreertos -llwip -lssl -ljson -lsmartconfig -lpwm -L./libesphttpd -lesphttpd -lwebpages-espfs user/.output/eagle/debug/lib/libuser.a driver/.output/eagle/debug/lib/libdriver.a upgrade/.output/eagle/debug/lib/libupgrade.a -Wl,--end-group -o .output/eagle/debug/image/eagle.app.v6.out
/home/ppt/t/build/esp8266/ESP8266_RTOS_SDK/examples/ESP8266_IOT_PLATFORM-master/../..//lib/libjson.a(cJSON.o):(.text.print_number+0x48): undefined reference to `floor'
/home/ppt/t/build/esp8266/ESP8266_RTOS_SDK/examples/ESP8266_IOT_PLATFORM-master/../..//lib/libjson.a(cJSON.o):(.text.print_number+0x148): undefined reference to `floor'
/home/ppt/t/build/esp8266/ESP8266_RTOS_SDK/examples/ESP8266_IOT_PLATFORM-master/../..//lib/libjson.a(cJSON.o):(.text.parse_value+0x14): undefined reference to `pow'
/home/ppt/t/build/esp8266/ESP8266_RTOS_SDK/examples/ESP8266_IOT_PLATFORM-master/../..//lib/libjson.a(cJSON.o):(.text.parse_value+0x270): undefined reference to `pow'
collect2: error: ld returned 1 exit status
-----------
check the lib,no -lm cmd,add the cmd but no m can find.why?

[ESP_Rubin]

please refer chapter 4 as link:
http://espressif.com/sites/default/file ... ide_en.pdf