Compiling i2c library gives string.h error

[rupin]

When I added the i2c driver, and ran make, i met with the following error.
/home/pi/esp8266/xtensa-toolchain-build/build-lx106/root/bin/xtensa-lx106-elf-gcc -mlongcalls -I/home/pi/esp8266/esp_iot_sdk_v0.9.3/include -Imyclib -Iinclude -Iuser -O2 -I/home/pi/esp8266/esp_iot_sdk_v0.9.3/include/ i2c/i2c.c user/user_main.c -flto -nostdlib -Wl,--relax -Wl,--gc-sections -L/home/pi/esp8266/esp_iot_sdk_v0.9.3/lib -L/home/pi/esp8266/xtensa-toolchain-build/build-lx106/gcc-4.9.1-elf/xtensa-lx106-elf/libgcc/libgcc.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/liblwip.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/libssl.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/libupgrade.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/libnet80211.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/liblwip.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/libwpa.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/libnet80211.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/libphy.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/libmain.a /home/pi/esp8266/esp_iot_sdk_v0.9.3/lib/libpp.a /home/pi/esp8266/xtensa-toolchain-build/build-lx106/gcc-4.9.1-elf/xtensa-lx106-elf/libgcc/libgcc.a -T /home/pi/esp8266/esp_iot_sdk_v0.9.3/ld/eagle.app.v6.ld -B/home/pi/esp8266/esp_iot_sdk_v0.9.3/lib -o image.elf
In file included from i2c/i2c.c:21:0:
/home/pi/esp8266/esp_iot_sdk_v0.9.3/include/osapi.h:8:20: fatal error: string.h: No such file or directory
#include <string.h>
^
compilation terminated.
user/user_main.c:1:20: fatal error: string.h: No such file or directory
#include <string.h>
^
compilation terminated.
Makefile:49: recipe for target 'image.elf' failed
make: *** [image.elf] Error 1

I am pretty sure my setup is broken, if you do have tips, please let me know.

[AuroraRAS]

Maybe you should follow these steps from this link:
https://github.com/esp8266/esp8266-wiki/wiki/Toolchain#installing-xtensa-libraries-and-headers

I had a same trouble and I fixed it.