make ucos_test错误

kylezk

+ linking o file ... : start.o at91_aic.o at91_usart.o at91_tc.o at91_init.o sk yeye_stdio.o skyeye_printf.o main_entry.o -> simple_test.elf
arm-elf-ld -p -X -T../../samples/samples.lds start.o --start-group ../ulib/libu c.a at91_aic.o at91_usart.o at91_tc.o at91_init.o skyeye_stdio.o skyeye_printf. o main_entry.o --end-group -o simple_test.elf
skyeye_printf.o: In function `getnum':
/home/skyeye-projects/ucosii4skyeye/samples/simple_test/../../lib/skyeye_printf .c:110: undefined reference to `isdigit'
skyeye_printf.o: In function `skyeye_printf':
/home/skyeye-projects/ucosii4skyeye/samples/simple_test/../../lib/skyeye_printf .c:156: undefined reference to `isdigit'
make: *** [simple_test.elf] 错误 1
怎么解决啊

epingnet

skyeye项目至今也有几年了吧，连一份完整的文档都没有，至于编译使用过程中出错很正常的了。