Не-не-не, опции компилятора я и сам вижу в makefile, вы покажите пожалуйста целую командную строку.
c:/Espressif/xtensa-lx106-elf/bin/xtensa-lx106-elf-gcc -Os -Wall -Wno-pointer-sign -fno-tree-ccp -mno-target-align -mno-serialize-volatile -foptimize-register-move -Wundef -Wpointer-arith -Werror -Wl,-EL -fno-inline-functions -nostdlib -mlongcalls -mtext-section-literals -DICACHE_FLASH -DPBUF_RSV_FOR_WLAN -DLWIP_OPEN_SRC -DEBUF_LWIP -I ./include -I ../include -I ../../include -I C:/ESP8266_test/esp8266web-master/include -I C:/ESP8266_test/esp8266web-master/app/include -o .output/eagle/obj/fost02.o -c fost02.c
fost02.c: In function 'ReadHMS':
fost02.c:230:12: error: floating constant truncated to zero [-Werror=overflow]
T.d=((float)(T.ul))*0.005 - PTATD1; //calc. Temperature from ticks to [C] 36.92 0.3
^
fost02.c:230:12: error: floating constant truncated to zero [-Werror=overflow]
fost02.c:234:12: error: floating constant truncated to zero [-Werror=overflow]
RH.d=(float)(RH.ul)*0.5;
^
fost02.c:236:12: error: floating constant truncated to zero [-Werror=overflow]
RH.d=(T.d-25.0)*(0.01+0.00008*RH.d)-0.0000028*RH.d*RH.d+0.0405*RH.d-4.0;
^
fost02.c:236:12: error: floating constant truncated to zero [-Werror=overflow]
fost02.c:236:12: error: floating constant truncated to zero [-Werror=overflow]
fost02.c:236:12: error: floating constant truncated to zero [-Werror=overflow]